U.S. National Wetland Inventory Classif ications as Predictors of the Occurrence of Columbia Spotted Frogs ( Rana luteiventris ) and Pacific Treefrogs ( Hyla regilla ) - James C. Munger; Mark Gerber; Katy Madrid; Martha‐Ann Carroll; Wade Petersen; Lisa Heberger (Conservation Biology, 1998)
In the Owyhee Mountains of southwestern Idaho, we compared the habitat characteristics of sites at which we captured Columbia spotted frogs (Rana luteiventris) and Pacific treefrogs (Hyla regilla) to habitat characteristics of sites without frogs. Our primary objective was to determine if National Wetland Inventory classifications can be used to predict the presence of these species. Adult spotted frogs tended to be at palustrine, shrubscrub, seasonally flooded sites or at intermittent riverine, streambed, seasonally flooded sites; they tended not to be at palustrine, emergent, seasonally flooded or at intermittent riverine, streambed, temporarily flooded sites. Spotted frog sites also tended to have more submerged vegetation and algae and less grass and sagebrush; they were more likely to be located at oxbows, pools, or ponds; and they were more likely to have obvious hiding places than were sites without spotted frogs. Sites where treefrog adults were found tended to be lower in willow and higher in grass and emergent and submerged vegetation; they were more likely to be at a pond or pool than were sites without treefrog adults. Treefrog larvae tended to be found at intermittent riverine, streambed, seasonally flooded sites or at palustrine, emergent, seasonally flooded sites; they tended not to be at palustrine, shrubscrub, seasonally flooded sites. Treefrog larval sites also were higher in silt, emergent vegetation, and algae and lower in sagebrush and willow, and they were more likely be located at a pond, oxbow, or pool than were sites without treefrog larvae. Although certain National Wetland Inventory classifications were associated with frog presence, none could be used to predict with complete assurance the presence or absence of either species. Logistic regression models using habitat measures were better at predicting the presence of amphibian species than were models using National Wetland Inventory classifications; models using a combination of habitat measures and National Wetland Inventory classifications performed best. Because of their ready availability in geographic information system data bases, however, National Wetland Inventory classifications may in some circumstances provide a valuable indicator of the likelihood of finding certain amphibian species. National Wetland Inventory classifications should be most useful for highly aquatic species in arid environments. Clasificaciones del Inventario Nacional de Humedales de E.U.A. como Predictores de la Aparición de la Rana Moteada de Columbia ( Rana luteiventris ) y la Rana Arborícola del Pacífico ( Hyla regilla ) En las montañas Owyhee el suroeste de Idaho, comparamos las características del hábitat de sitios donde capturamos la rana moteada de Columbia (Rana luteiventris) y la rana arborícola del Pacífico (Hyla regilla) con sitios sin ranas. Nuestro objetivo principal fue el de determinar si las clasificaciones del Inventario Nacional de Humedales pueden ser utilizados para predecir la presencia de estas especies. Los adultos de la rana moteada tienden a utilizar sitios palustres, arbustivos, estacionalmente inundados, o sitios reverinos intermitentes, camas de arroyos, estacionalmente inundados, pero no sitios palustres, emergentes, estacionalmente inundados o intermitentemente riverinos, camas de arroyos, temporalmente inundados. Los sitios para la rana moteada tambien tienden a tener mas vegetación sumergida y algas y menos pasto y salvia; fue mas probable localizarlas en estanques, meandros y charcos, donde es probable localizar mas sitios de refugio que en sitios sin ranas moteadas. Los sitios donde se encontraron ranas arborícolas adultas tendían a tener pocos sauces, mucho pasto y vegetación emergente y sumergida, también fueron mas comunes los estanques y charcos, que en sitios sin ranas arborícolas. Las larvas de las ranas arborícolas tienden a ser encontradas en sitios riverinos intermitentes, camas de arroyo, estacionalmente inundados, o en sitios palustres, emergentes, estacionalmente inundados; pero no en sitios palustres, arbustivos, estacionalmente inundados. Las larvas de la rana arborícola frecuentan sitios con alto contenido de arcilla, vegetación emergente y algas, bajas en salvia y sauces y fueron mas probables de localizar en estanques, meandros y charcos que en sitios sin larvas de ranas arborícolas. Aunque algunas clasificaciones del Inventario Nacional de Humedales estan asociadas con la presencia de ranas, ninguna puede ser usada para predecir con completa certeza la presencia o ausencia de alguna de las dos especies. Modelos de regresión logística con datos del hábitat resultaron ser mejores en la predicción de la presencia de especies de anfibios que los modelos con las clasificaciones del Inventario Nacional de Humedales. Los mejores modelos resultaron ser aquellos que combinaron las mediciones del hábitat y las clasificaciones del Inventario Nacional de Humedales. Debido a su fácil acceso a través del bases de datos de Sistemas de Información Geográfica, las clasificaciones del Inventario Nacional de Humedales podrían sin embargo en algunas circunstancias proveer un indicador valioso de la probabilidad de encontrar ciertas especies de anfibios. Las clasificaciones del Inventario Nacional de Humedales podrían tener mas aplicación para especies altamente acuáticas en ambientes áridos.

Effects of Forest Fragmentation on Recruitment Patterns in Amazonian Tree Communities - William F. Laurance; Leandro V. Ferreira; Judy M. Rankin-De Merona; Susan G. Laurance; Roger W. Hutchings; Thomas E. Lovejoy (Conservation Biology, 1998)

The Influence of Geomorphological Heterogeneity on Biodiversity I. A Patch-Scale Perspective - Michael R. Burnett; Peter V. August; James H. Brown; Keith T. Killingbeck (Conservation Biology, 1998)

Broadening the Extinction Debate: Population Deletions and Additions in California and Western Australia - Richard J. Hobbs; Harold A. Mooney (Conservation Biology, 1998)

Mitochondrial DNA Phylogeography of the North American Brown Bear and Implications for Conservation - Lisette P. Waits; Sandra L. Talbot; R. H. Ward; G. F. Shields (Conservation Biology, 1998)
The historical distribution of the brown bear (Ursus arctos) in North America included Alaska, western Canada, the western and midwestern states, plus northern Mexico. Currently, the brown bear is limited to Alaska, the Canadian provinces of the Yukon, Northwest Territories, British Columbia, and Alberta, and six threatened subpopulations in the lower 48 states. To examine the evolutionary history of U. arctos in North America and to assess the genetic divergence between individuals from different geographic regions, we obtained 294 nucleotides of mitochondrial DNA sequence data from the control region for 317 free‐ranging brown bears. Twenty‐eight unique sequences, or mitochondrial DNA haplotypes were detected. The average sequence divergence between haplotypes was high (4.3%), and some haplotypes differed by as many as 23 nucleotides. Phylogenetic analyses using maximum parsimony revealed four major mitochondrial DNA phylogeographic groups, or clades. The significant phylogeographic structure detected in brown bears strongly contrasts with results obtained for other large carnivores and suggests limited female‐mediated gene flow. The mitochondrial DNA phylogeographic clades do not correlate with taxonomic classifications for U. arctos, and we hypothesize that the clades were formed prior to migration of this species into North America. We suggest evolutionarily significant units for conservation in three geographic regions: (1) the Alaskan islands of Admiralty, Baranof, and Chichagof; (2) mainland Alaska, Kodiak Island, and northern Canada; and (3) southern British Columbia, southern Alberta, and the states of Idaho, Montana, and Wyoming. Filogenia del ADN Mitocondrial del Oso Café de Norte América y sus Implicaciones en la Conservación La distribución histórica del oso café (Ursus arctos) en Norte Améica includía Alaska, oeste de Canada, oeste y medio oeste de los Estados Unidos y Norte de México. Actualmete, el oso café esta limitado a Alaska, las provincias Canadienses de Yukon, Northwest territories, British Columbia, Alberta y seis subpoblaciones amenazadas en 48 estados de los Estados Unidos. Obtuvimos datos de secuencias de 294 nucleótidos de ADN mitocondrial de la región control de 317 osos cafes para examinar la historia evolutiva de U. arctos en Norte América y evaluar la divergencia genética entre individuos de diferentes regiones geográficas. Fueron detectadas veintiocho secuencias únicas o haplotipos de ADN mitocondrial. El porcentaje de secuencia divergente entre haplotipos fue alto (4.3%) y algunos haplotipos difirieron por tantos como 23 nucleótidos. Análisis filogenéticos usando maxima parsimonia revelaron cuatro grupos mayores de ADN mitocondrial filogeográfico. La estructura filogeografica significativa detectada en osos cafés contrasta fuertemente con resultados obtenidos de otros carnivoros mayores y sugiere flujo genético limitado, mediado por las hembras. Los grupos de ADN mitocondrial filogeográfico no se correlacionan con clasificaciones taxonómicas de U. arctos, nosotros hipotetizamos que los grupos fueron formados antes de las migraciones de esta especie hacia Norte América. Sugerimos unidades evolutivamente significativas para su conservación en tres regiones geográficas: 1) las islas Admiralty, Baranof y Chichagof de Alaska; 2) el territorio continential de Alaska, la isla Kodiak y el norte de Canada, y 3) Sur de British Columbia, sur de Alberta y los estados de Idaho, Montana y Wyoming en los Estados Unidos.

Extinction and Persistence of Rare Orchids in Veracruz, Mexico - Victoria Sosa; Teodoro Platas (Conservation Biology, 1998)

Bats and the Loss of Tree Canopy in African Woodlands - M. Brock Fenton; David H. M. Cumming; I. L. Rautenbach; Graeme S. Cumming; Meg S. Cumming; Gavin Ford; Russell D. Taylor; Jenna Dunlop; Mark D. Hovorka; Dave S. Johnston; Christine V. Portfors; Matina C. Kalcounis; et al. (Conservation Biology, 1998)

Impact of Forest Fragmentation on Seedling Abundance in a Tropical Rain Forest - Julieta Benitez‐Malvido (Conservation Biology, 1998)
To evaluate the impact of fragmentation on forest regeneration, I measured the abundance of shade‐tolerant, mature‐phase tree seedlings (individuals 5–100 cm tall) in unfragmented and fragmented vegetation in three sites near Manaus, Brazil. The habitats studied were (1) continuous forest (control, n = 5); (2) 100‐ha fragments (n = 2); (3) 10‐ha fragments (n = 4); and (4) 1‐ha fragments (n = 5). For 10‐ and 100‐ha fragments, seedling density was measured in the center, the edge, and the corner of the fragments, and at 20‐m intervals up to 100 m away from the fragment’s edge. The density of seedlings declined significantly from continuous forest to forest fragments. Corners of 100‐ha fragments had lower densities of seedlings than plots in centers and edges. In both 100‐ and 10‐ha fragments, edge seedling density increased toward forest interior, but the increment was significant for only one site. Edge effects were more important than area effects per se in affecting seedling abundance. Overall, the centers of larger fragments (100 ha) did not have significantly higher densities of tree seedlings than smaller ones (10 and 1 ha). I suggest that a decrease in seed rain produced by increased tree mortality, reduced seed output and dispersal, high seed predation, and lower seedling establishment might explain the lower seedling numbers observed in forest fragments and fragment edges. These results suggest that forest fragmentation at Manaus may affect the regenerative potential of the forest. Impacto de la Fragmentación Forestal en la Abundancia de Plántulas en un Bosque Tropical Lluvioso Para evaluar el impacto de la fragmentación sobre la regeneración de la selva, utilizé la abundancia de plántulas (individuos entre 5 y 100 cm de altura) de árboles tolerantes a la sombra o de bosque maduro, como indicador de la alteración. Censé la abundancia de plántulas en sistemas no fragmentados y fragmentados en tres sitios (A, B, y C) al norte de Manaus, Brasil. Los hábitats estudiados fueron: (1) selva virgen (control, n = 5); (2) fragmentos de 100 ha (n = 2); (3) fragmentos de 10 ha (n = 4); y (4) fragmentos de 1 ha (n = 5). Para los fragmentos de 100 y de 10 ha la densidad de plántulas se midió en el centro, el borde y en la esquina de los fragmentos y también, a intervalos de 20 m, hasta 100 m del borde. La densidad de plántulas (número de plántulas/m 2 ) decreció significativamente de la selva virgen a los fragmentos de diferentes tamaños. Las esquinas de los fragmentos de 100 ha tuvieron menor número de plántulas que los centros y los bordes. En los fragmentos de 100 y 10 ha, la densidad de plántulas aumentó del borde hacia el interior del fragmento, pero éste incremento fue significativo únicamente para el Sitio B. Los efectos de borde parecen tener un impacto mayor sobre la abundancia de plántulas que el tamaño del fragmento. Los centros de los fragmentos de mayor tamaño (100 ha) tuvieron una densidad de plántulas similar a los menores (10 y 1 ha). La información existente y los resultados obtenidos en este trabajo, sugieren que una disminución en la lluvia de semillas, producida por un incremento en la mortalidad de árboles, una dispersión reducida, alta predación, y un pobre desempeño de las plántulas pueden explicar la disminución en el número de plántulas en los fragmentos y en los bordes de los fragmentos. Todo parece indicar que la fragmentación, en este sitio, puede afectar el potencial regenerativo de la selva.

Threatened Beetles in White-Backed Woodpecker Habitats - Petri Martikainen; Lauri Kaila; Yrjo Haila (Conservation Biology, 1998)

Effects of Silvicultural Edges on the Distribution and Abundance of Amphibians in Maine - Phillip G. Demaynadier; Malcolm L. Hunter (Conservation Biology, 1998)
Amphibians share several biological characteristics that may cause them to be sensitive to abrupt transitions in microhabitat and microclimate that occur across forest edges. To better understand the importance of edge effects on amphibians in a forested landscape, we sampled the distribution of populations along drift fences placed perpendicular to silvicultural edges of varying contrast in central Maine. Within the community of amphibians sampled (14 species), salamanders generally were more sensitive to even‐aged harvesting and associated edge effects than were anurans, but forest habitat generalists and specialists were identified within both groups. We conservatively estimated the depth of edge effects at 25–35 m for a subset of management‐sensitive species (Plethodon cinereus, Ambystoma maculatum, A. laterale, and Rana sylvatica). An index of edge contrast, calculated using ambient light penetration levels, was valuable in predicting the magnitude of edge effects among sites that included silvicultural edges of different age and origin (old field plantations versus recent clearcuts). Some structural microhabitat variables relevant to forest management were identified as potentially limiting to amphibians near forest edges, including canopy cover, litter cover, and a measure of stumps, snags, and their root channels. Our observations are consistent with the results of other work on biotic edge effects in the eastern United States and suggest that impacts from intensive forest management practices extend beyond the boundaries of harvested stands. Efectos de Bordes Silviculturales en la Distribución y Abundancia de Anfibios en Maine Los anfibios comparten diversas characterísticas biológicas que pueden ser la causa de que sean sensitivos a transiciones abruptas en microhábitats y microclimas que ocurren a lo largo de los bordes de bosques. Para entender mejor la importancia de los efectos de bordes en anfibios en un paisaje boscoso, muestreamos la distribución de poblaciones a lo largo de vallas de desvío colocadas perpendicularmente a bordes silviculturales de contrastes variantes en la parte central de Maine, USA. Dentro de la comunidad de anfibios muestreados (14 spp), las salamandras generalmente fueron más sensitivas a la tala de edad constante y efectos asociados al borde que los anuros, pero tanto especies generalistas y especialistas de hábitat boscoso fueron identificadas dentro de ambos grupos. Conservativamente estimamos la profundidad del efecto de borde a 25–35m para un subset de especies sensitivas al manejo (Plethodon cinereus, Ambystoma maculatum, A. Laterale y Rana sylvatica). Un índice de constraste de borde, calculado usando niveles de penetración de luz ambiental fue valioso para predecir la magnitud de los efectos de borde entre sitios que incluyeron bordes silviculturales a diferentes edades y origenes (plantaciones viejas contra clareados recientes). Algunas variables estructurales de microhábitat relevantes para el manejo forestal fueron identificadas como potencialmente limitantes para anfibios cercanos a los bordes de bosques, incluyendo la cobertura del dosel, cobertura de hojarasca y una medición de varas, tocones y sus canales de raíces. Nuestras obsevaciones son consistentes con los resultados de otro trabajo en efectos bióticos de borde en el este de los Estados Unidos y sugieren que los impactos de prácticas de manejo forestal intensivo se extienden mas allá de los límites de los sitios cosechados.

A Meta‐Analysis of Forest Cover, Edge Effects, and Artificial Nest Predation Rates - Mitschka J. Hartley; Malcolm L. Hunter (Conservation Biology, 1998)

The Influence of Geomorphological Heterogeneity on Biodiversity II. A Landscape Perspective - William F. Nichols; Keith T. Killingbeck; Peter V. August (Conservation Biology, 1998)

Range Collapse, Re-Introductions, and Biogeographic Guidelines for Conservation - Mark V. Lomolino; Rob Channell (Conservation Biology, 1998)

Training Idiot Savants : The Lack of Human Dimensions in Conservation Biology - Susan K. Jacobson; Mallory D. Duff (Conservation Biology, 1998)

The Influence of Geomorphological Heterogeneity on Biodiversity I. A Patch‐Scale Perspective - Michael R. Burnett; Peter V. August; James H. Brown; Keith T. Killingbeck (Conservation Biology, 1998)
Landscapes composed of spatially heterogeneous abiotic conditions should provide a greater diversity of potential niches for plants and animals than do homogeneous landscapes. We tested this hypothesis in a deciduous forest ecosystem in the northeastern United States. We created an index that summarizes the collective variation in terrain and soil properties in 2‐ha study plots. We measured woody plant species richness and diversity in 20 study plots that had high geomorphological heterogeneity and 20 plots that had low geomorphological heterogeneity. The richness and diversity of trees and shrubs were significantly higher in sites with high geomorphological heterogeneity than in sites that exhibited little change in terrain or soil conditions. Variation in aspect and soil drainage were especially important predictors of biotic diversity. Our results demonstrate an intimate association between abiotic and biotic diversity and have significant implications for long‐term conservation strategies. Influencia de la Heterogeneidad Geomorfológica en la Biodiversidad I. Una Perspectiva a Escala de Parcela Los paisajes compuestos de condiciones abioticas espacialmente heterogeneas deberían proveer una gran diversidad de nichos potenciales para plantas y animales comparados con los paisajes homogéneos. Probamos esta hipótesis en un ecosistema de bosque deciduo del noroeste de los Estados Unidos de Norteamérica. Creamos un índice que sumariza la variación colectiva de las condiciones del terreno y las propiedades del suelo en áreas de estudio de 2 ha. Medimos la riqueza de especies de madera y la divresidad de 20 áreas de estudio con una alta heterogeneidad geomorfológica y 20 con baja heterogeneidad geomorfológica. La riqueza y diversidad de especies de árboles y arbustos fue significativamente mayor en sitios con alta heterogeneidad geomorfológica en comparación con sitios que exhibieron pocos cambios en las condiciones del terreno o del suelo. Variaciones en el aspecto y drenaje del suelo fueron indicadores especialmente importantes de la diversidad biótica. Nuestros resultados demuestran que existe una asociación intima entre diversidad biótica y abiótica, teniendo implicaciones significativas en las estrategias de conservación a largo plazo.

Effects of Forest Fragmentation on Recruitment Patterns in Amazonian Tree Communities - William F. Laurance; Leandro V. Ferreira; Judy M. Rankin‐De Merona; Susan G. Laurance; Roger W. Hutchings; Thomas E. Lovejoy (Conservation Biology, 1998)

Life, the Universe, and Everything - Tormod V. Burkey; Jari Niemelä; N. N. FitzSimmons; Jeff Langholz; Sharon J. Downes; T. R. McClanahan (Conservation Biology, 1998)

Jacques Cousteau and His World's Inspiring Beauty - Alejandro Grajal (Conservation Biology, 1998)

Successful Reintroduction of Captive‐Raised Yellow‐Shouldered Amazon Parrots on Margarita Island, Venezuela - Virginia Sanz; Alejandro Grajal (Conservation Biology, 1998)
The Yellow‐shouldered Amazon (Amazona barbadensis) is one of the most endangered species of parrots in Venezuela. An integrated conservation program has focused on reversing the causes of parrot population decline on the Macanao Peninsula in Margarita Island. As a result, the parrot population on the island has increased to about 1900 individuals in 1996 from an estimated population of 750 in 1989, when the project started. Cooperation from national and local authorities and the project’s community outreach have resulted in several confiscated chicks. Whereas most confiscated chicks were successfully reintroduced in a cross‐fostering nest program, some had to be kept in captivity for later release. We hand‐reared 14 A. barbadensis and housed them for a year in a large outdoor aviary. Before release the birds were screened to determine their general health. Four parrots were fitted with radio transmitters and monitored for a minimum of 11 months. All 4 birds with radio transmitters survived and adapted successfully to their natural environment, 10 of the 12 released parrots survived at least 1 year, and 1 was seen alive 34 months after release. Integration into wild groups varied from 5 days to 9 months, with the two youngest parrots showing a slower integration process. None of the parrots reproduced the first year after release. Later three were seen scouting nesting holes with their partners, and one of the parrots was confirmed attending a nest with three eggs 28 months after release. Two chicks fledged from this nest. A substantial portion of the success of this program rests on 5 years of previous work on environmental education, public awareness, and studies on the parrot’s biology. To provide some guidance on the costs of reintroduction projects, we estimated an overall expenditure of about U.S. $2800 per parrot. Previous attempts to reintroduce captive‐raised parrots have had limited success, and our study indicates that reintroduction is feasible when captive‐raised parrots are introduced to an area with a resident population. Although reintroduction can significantly reduce the chances of extinction, it also involves some risks. The long‐term solution against extinction of A. barbadensis will be a combination of scientific understanding of their biology and habitat, awareness by local human communities, reduction in the wild bird trade, and continued commitment by conservation enforcement agencies. Reintroducción Exitosa del Loro Espalda Amarilla del Amazonas Criados en Cautiverio en la Isla Margarita, Venezuela La cotorra cabeziamarilla (Amazona barbadensis) es uno de los loros más amenazados de Venezuela. Un programa integrado de conservación se enfocó a revertir las causas de la declinación poblacional de cotorras en la Península de Macanao, en la Isla de Margarita. Como resultado, la población total de cotorras en la isla se incrementó hasta los 1900 individuos en 1996, a partir de una población estimada de 750 individuos cuando comenzó el proyecto en 1989. La cooperación de las autoridades nacionales y locales y las actividades educativas, han conducido a varios decomisos de polluelos. Aun cuando la mayoría de los polluelos fueron reintroducidos en un exitoso programa de nidos nodriza, algunos se tuvieron que mantener en cautiverio para soltarlos después. Para este estudio, un total de 14 A. barbadensis fueron criadas a mano y albergadas en un gran aviario durante un año. Antes de soltarlas, las aves fueron sometidas a análisis de salud general. Se le pusieron radio transmisores a cuatro cotorras, y se monitorearon por 11 meses. Todas las cuatro cotorras con radio transmisores sobrevivieron y se adaptaron exitosamente a su ambiente natural, 10 de las 12 cotorras sobrevivieron al menos durante un año, y una cotorra estaba viva al menos 34 meses después de soltarlas. La integración a grupos silvestres varió entre 5 días y 9 meses, y las dos cotorras mas jóvenes mostraron un proceso de integración más lento. Ninguna de las cotorras se reprodujo el primer año después de soltarlas. Tres de las cotorras fueron vistas explorando oquedades con sus parejas durante el segundo año, y una cuarta fue vista atendiendo un nido con tres huevos, a los 28 meses después de soltarla. Dos polluelos volaron de este nido. Una parte significativa del éxito de este estudio se basa en 5 años de trabajo previo en educación ambiental, conocimiento del publico, y estudios de biología de las cotorras. Para guiar los costos de proyectos de reintroducción, estimamos que el costo total estuvo alrededor de U.S.$2800 por cotorra. Pruebas anteriores para reintroducir loros criados en cautiverio han tenido éxito limitado. Los resultados de nuestro estudio indican que la reintroducción es posible cuando los loros criados en cautiverio son introducidos en un área donde existe una población silvestre residente. Aún cuando la reintroducción puede contribuir a reducir las oportunidades de extinción de esta y otras especies de cotorras, también acarrea riesgos. La solución a largo plazo contra la extinción será una combinación de entendimiento científico de la biología y habitat, conocimiento por parte de las comunidades humanas locales, reducción de la demanda de aves silvestres para el tráfico de mascotas, y la dedicación y continuidad de agencias conservacionistas y de guardería.

Influence of Complex Sex Determination on Demographic Stochasticity and Population Viability - Paul Leberg (Conservation Biology, 1998)

Softening the Boundaries - Gary K. Meffe (Conservation Biology, 1998)

Impact of pulp and paper mill effluent on water quality and fauna in a New Zealand hydro‐electric lake - Angela D. Sharples; Clive W. Evans (New Zealand Journal of Marine and Freshwater Research, 1998)
The Kinleith pulp and paper mill discharges effluent into the Kopakorahi arm of Lake Maraetai (New Zealand) resulting in an effluent gradient defined by the effluent visibility (Secchi disc), transmittance (465 nm), temperature, and oxygen level that is discernible at least as far down stream as the adjoining Lake Waipapa. This effluent gradient is reflected in the composition of the fauna caught in fyke nets which at the most effluent‐exposed sites is dominated by goldfish ( Carassius auratus ) and is depauperate in pollution‐sensitive species such as freshwater crayfish ( Paranephrops planifrons ) and trout ( Salmo trutta and Oncoryhynchus mykiss ) In 1991 the Kinleith mill undertook substantial process modifications which have resulted in improvements in the water quality of the discharge. Secchi disc visibilities have increased markedly at the most effluent‐exposed sites since modernisation of the mill and similar improvements have been observed in light transmittance. A seasonal trend in water temperature not previously observed was recorded at the most effluent‐exposed sites following modernisation, and dissolved oxygen levels at these sites rose markedly. Improvements in the water quality of the recipient since the mill modernisation are reflected in changes in the sampled fauna in particular the occurrence of trout at sites from which they were previously absent.

Effects of turbidity on the feeding ability of the juvenile migrant stage of six New Zealand freshwater fish species - David K. Rowe; Tracie L. Dean (New Zealand Journal of Marine and Freshwater Research, 1998)
Laboratory tank experiments were used to determine the effect of turbidity levels ranging from 0–640 Nephelometric Turbidity Units (NTU) on mean feeding rates for each species. Mean feeding rates for banded kokopu ( Galaxias fasciatus ), smelt ( Retropinna retropinna ), inanga ( G. maculatus ), and common bullies ( Gobiomorphus cotidianus ) were all reduced by increased turbidity, but significantly so only for banded kokopu and inanga. Banded kokopu was the most sensitive species as feeding rates at 20 NTU were significantly lower than in clear water, compared with levels over 160 NTU for the other species. Feeding rates for redfinned bullies ( Gobiomorphus huttoni ) increased with turbidity up to 40 NTU then decreased. Reductions in feeding rate at elevated turbidity levels were the result of a reduced inability to feed, rather than to stress, as exposure to the highest turbidity level did not reduce feeding motivation or appetite. Feeding tests in the dark indicated that, whereas vision was important for feeding by all species, banded kokopu and common bullies had a comparatively well‐developed ability to feed using non‐visual senses. Non‐visual feeding may have reduced the impact of high turbidity levels on feeding for these two species, and could confound attempts to determine the effects of turbidity on visual feeding on live prey.

SQMCI: A biotic index for freshwater macroinvertebrate coded‐abundance data - John D. Stark (New Zealand Journal of Marine and Freshwater Research, 1998)
A new freshwater macroinvertebrate‐based biotic index derived from the Quantitative Macroinvertebrate Community Index (QMCI) is proposed for use with coded‐abundance data collected from stony New Zealand streams using hand nets. The SQMCI (Semi‐Quantitative MCI) responds to changes in community dominance in a similar manner to the QMCI, but requires fewer replicate samples to achieve the same precision. In situations where macroinvertebrate densities are not required, the SQMCI provides a similar assessment to the QMCI with less than 40% of the effort, thus reducing the cost and/or improving the scientific defensibility of biomonitoring programmes. Variability of biotic indices must be known to enable detection of significant differences in water quality between streams, at different sites in the same stream, or between times at the same site. Best estimates of MCI and QMCI standard deviations have been updated, and newly derived for the SQMCI, for use in two statistical procedures for testing for significant differences between paired index values.

New Zealand fur seals ( Arctocephalus forsten ) at the Snares Islands: A stabilised population? - P. W. Carey (New Zealand Journal of Marine and Freshwater Research, 1998)
The abundance and distribution of New Zealand fur seals ( Arctocephalus forsteri ) on the Snares Islands were investigated in February 1984 and in March 1997. In 1984, a total of 1683 adult fur seals were counted in a census that included all islands in the Snares group. Twenty‐five per cent of these were found on the hitherto uncounted islets of the Western Chain. In 1997, 1324 adults were counted on North East and Broughton Islands. In 1984, 164 pups were counted in the entire archipelago, whereas 171 pups were seen on North East and Broughton Islands in 1997. Sixteen breeding sites were identified including six sites that were new in 1984, and one new in 1997. It is suggested that the fur seal population on the Snares is now spatially limited and may have stabilised after a period of relatively rapid growth in the 1950s and 1960s.

Surface water‐quality modeling. By Steve C.Chapra. Published in 1997 by McGraw‐Hill, New York, United States. 844 p. ISBN: 0–07–011364–5. - J. C. Rutherford (New Zealand Journal of Marine and Freshwater Research, 1998)

Occurrence of the tropical and subtropical gastropod Strombus vomer vomer (Roding, 1798) (Mollusca: Strombidae) off north‐eastern Northland, New Zealand - Bruce A. Marshall; Derrick D. Crosby (New Zealand Journal of Marine and Freshwater Research, 1998)
Strombus vomer vomer (Roding 1798) is recorded from north‐eastern Northland, New Zealand, the first record of the family Strombidae from New Zealand Recent fauna. Some other New Zealand records of tropical and subtropical Mollusca are commented upon.

Embryology and early larval development of orange roughy ( Hoplostethus atlanticus Collett) - John R. Zeldis; Paul J. Grimes; Alan C. Hart (New Zealand Journal of Marine and Freshwater Research, 1998)
Orange roughy ( Hoplostethus atlanticus Collett) egg development is described from fertilisation in a series of 29 stages based on morphological criteria. Two early larval stages are also described. Observations were made of eggs obtained from strip‐fertilisation using trawl‐caught adults and from plankton net samples of eggs caught off the east coast of New Zealand, and then cultured on‐board ship. Live eggs of each stage are described and illustrated with line drawings and photographs and age‐at‐stage data are presented. The mean development times from fertilisation to hatching were 278 h at 8°C, 235 h at 10°C, and 146 h at 12°C. Eggs cultured at 6°C did not hatch. The mean length of the larvae at hatching was 5.33 mm notochord length. Most criteria used in staging are readily observable with a standard dissecting microscope at x25 magnification using transmitted light. Damaged eggs are common in egg production surveys for orange roughy. The staging of damaged eggs is described. Orange roughy eggs can be sorted easily from plankton samples collected during egg production surveys for orange roughy biomass, and staged on‐board ship before preservation.

Short period (1–4 h) sea level fluctuations on the Canterbury coast, New Zealand - Derek G. Goring; R. Falconer Henry (New Zealand Journal of Marine and Freshwater Research, 1998)
Data from six sea level sites on the Canterbury coast, New Zealand, were analysed for short period (1–4 h) waves. Persistent waves with periods of 3.4 h in Pegasus Bay and 2.4 h in the Canterbury Bight were found. Their amplitude and phase are highly variable. Edge waves of similar period were found in simulations using a 2‐dimensional, harmonic, shallow water, numerical model. Numerical and analytical modelling showed that the offshore decay in amplitude may be approximated by Stokes zero‐mode edge waves, but the numerical model revealed that the detailed structure of the offshore decay is more complicated than can be explained by analytical models using a semi‐infinite sloping beach. Rotation appears to have little effect. In Pegasus Bay the edge waves are trapped laterally between the northern extent of the bay and Banks Peninsula and offshore by the shelf. In the Canterbury Bight they are trapped laterally between Banks Peninsula and the curvature of the coast and offshore by the shelf. The origin of the waves and the reason for their variability are unclear, but may be the result of the non‐linear interaction between semidiurnal tides and meteorological effects.

Hydrodynamics of Manukau Harbour, New Zealand - Robert G. Bell; Sergei V. Dumnov; Bryan L. Williams; Malcolm J. N. Greig (New Zealand Journal of Marine and Freshwater Research, 1998)
A calibrated two‐dimensional finite‐element model, which handles flooding/drying of intertidal areas, complemented by field data, has produced information on tidal propagation in Manukau Harbour, New Zealand with reasonably good accuracy. Excluding the upper‐harbour inlets, c. 50% of both the amplification and phase lag in the dominant M 2 tidal constituent occurs through the deep 10‐km‐long entrance channel to Puponga Point. The calculation of tidal residuals has isolated flood‐directed and ebb‐directed residual circulation respectively on either side of Puponga Point, which is a typical pattern for alternating flows around headlands. The model has established the dominance of tidal‐driven over wind‐driven circulation in most of the harbour except in the upper intertidal areas. Wind‐driven circulation in the inner Harbour is characterised by downwind flows over intertidal sand banks with pressure‐driven return flows (vertically averaged) in the deeper main channels. Tidal dissipation rates are sufficiently high to inhibit the onset of any summer stratification.

New Zealand sea lion predation on New Zealand fur seals - Corey J. A. Bradshaw; Chris Lalas; Shaun Mcconkey (New Zealand Journal of Marine and Freshwater Research, 1998)
Several sea lion species are known to occasionally hunt fur seals for food, but there have been few reports of New Zealand (Hooker's) sea lions {Phocarctos hookeri ) hunting and eating New Zealand fur seals ( Arctocephalus forsteri ) We describe the first reported incidence of P. hookeri eating A. forsteri pups in mainland New Zealand, and present evidence suggesting that it was active predation rather than scavenging. In late April, early May, and early September 1997 we found three sea lion regurgitations containing the remains of fur seal pups on Otago Peninsula, New Zealand. One contained three plastic tags formerly placed on three different female fur seal pups from a nearby breeding colony. When ingested at least two of the three identifiable pups fell within the lower condition quartile calculated from pups at their natal colony. The incidence of such predation may increase with increasing densities of both fur seals and sea lions in Otago, but the impact on the trends in fur seal populations is, and should remain, low.

Effect of temperature on the breeding cycle and spawning success of the New Zealand abalone, Haliotis australis - Graeme A. Moss (New Zealand Journal of Marine and Freshwater Research, 1998)
Adult Haliotis australis were brought into breeding condition in the hatchery by holding at constant temperature and ad libitum feeding of a mixed diet of seaweeds. Spawnings were achieved after 21 weeks at 15°C. This period was reduced to 14 weeks by raising the holding temperature to 18°C for 2 weeks before testing. More of those H. australis held at 18°C were induced to spawn and they produced a greater number of viable gametes. No spawnings were achieved from those H. australis tested within 1–2 days of collection from the wild.

Near‐shore distribution and abundance of dolphins along the West Coast of the South Island, New Zealand - Stefan Brager; Karsten Schneider (New Zealand Journal of Marine and Freshwater Research, 1998)
Compared to other stretches of the New Zealand coast, very little is known about the cetacean fauna off the West Coast of the South Island. The purpose of this paper is to describe the near‐shore distribution and abundance of dolphins in that area by summarising the results of two major studies. Between February 1995 and February 1997, 97 day trips were undertaken from Westport, Greymouth, and Jackson Bay in a small boat to survey the near‐shore distribution of dolphins. Between July 1994 and February 1997, 283 field days were spent on the water in Doubtful Sound studying the local bottlenose dolphin ( Tursiops truncatus ) population of c. 63 individuals. At the same time, three longer surveys were undertaken into other fiords of Fiordland which indicated the presence of further populations. Altogether, five delphinid species were recorded in various abundances. Small‐medium‐sized groups of Hector's dolphins ( Cephalorhynchus hectori ) with 1–60 individuals were observed in almost all areas of Westland in winter as well as in summer. Maximum densities peaked at 5–18 individuals per nautical mile of coastline between Cape Foulwind and Hokitika. Dusky and common dolphins ( Lagenorhynchus obscurus and Delphinus delphis ) occurred almost exclusively in summer in groups of 2–150 individuals, often with calves, especially at Cape Foulwind and Jackson Head. Bottlenose dolphins ( Tursiops truncatus ) and killer whales ( Orcinus orca ) were observed rarely off Westland, but occurred more frequently in Fiordland.

Ovarian development and the potential annual fecundity of western stock hoki ( Macruronus novaezelandiae ) - Kathy A. Schofield; Mary E. Livingston (New Zealand Journal of Marine and Freshwater Research, 1998)
Hoki ( Macruronus novaezelandiae ) form two of New Zealand's largest spawning fisheries, one centred off the west coast of the South Island (WCSI), the other in Cook Strait. Research data collected during surveys 1983–96 show that ovarian development begins on the feeding grounds between March and April, whereas spawning occurs mainly in July and August. Research has also shown that a significant proportion of adult hoki do not develop to spawn in a given year. Plans to estimate the absolute abundance of the western spawning stock off the WCSI using an egg production method require estimates of total annual fecundity and proportion spawning. Although determinate spawners, hoki are capable of multiple spawning in one season, and it is difficult to differentiate between fish about to spawn and fish that have already begun to spawn on the WCSI. In this study, we applied a modified stereological technique to samples of western stock hoki obtained from the feeding grounds south of New Zealand in May to determine the feasibility of estimating fecundity, at the same time as estimating the annual proportion developing to spawn. Mean fecundity estimates ranged from 0.4 million to 3.0 million oocytes and compare favourably with previous unpublished estimates of fecundity in early spawners on the west coast. We concluded that samples collected from the Southern Plateau during surveys of pre‐spawning hoki in May could provide useful estimates of fecundity.

Characterisation of lowland streams using a single‐station diurnal curve analysis model with continuous monitoring data for dissolved oxygen and temperature - Robert J. Wilcock; John W. Nagels; Graham B. McBride; Kevin J. Collier; Brent T. Wilson; Beat A. Huser (New Zealand Journal of Marine and Freshwater Research, 1998)
Twenty‐three lowland streams throughout the Waikato region, New Zealand, in catchments having a wide range of land uses and intensities, were monitored continuously over 3–4‐day periods for changes in dissolved oxygen (DO) and temperature. A single‐station diurnal curve model, DOFLO (Dissolved Oxygen at Low Flow), was used to produce reach‐averaged values for: K 2(20) , the reaeration coefficient at 20°C; P max. , the maximum daily rate of photosynthetic production of oxygen; R 20 , the daily respiration rate at 20°C; and Q 10 , the ratio of respiration rates 10°C apart. In addition, 24‐h average values for the ratio P/R were calculated and maximum and minimum values of DO and temperature tabulated for each site. Values of K 2(20) (0.05–40 d ‐1 , median 6.0 d ‐1 ) were in broad agreement with values calculated using a modified form of the O'Connor‐Dobbins equation. Values of gross primary production in daylight (0.5–29.2 g m ‐2 d ‐1 ) calculated from P max . (1.75–86.5 g m ‐3 d ‐1 ) were similar to data reported for other streams in agriculturally developed catchments in New Zealand and North America. Respiration rates (3.50–55.0 g m ‐3 d ‐1 ) were generally larger than values reported in the literature, and P/R ratios were mostly well below 1.0, indicative of heterotrophic respiration associated with decaying vegetation and other organic inputs and consistent with diurnal DO excursions of 40 to ≥120% saturation being commonly observed. Maximum daily temperatures up to 25.7°C (median 20.5°C) were weakly negatively correlated with DO minima. Five groupings of streams were identified from DOFLO parameter values, with K 2(20) being most critical in regulating average DO deficits.

Influence of substrate type and physico‐chemical conditions on macroinvertebrate faunas and biotic indices of some lowland Waikato, New Zealand, streams - Kevin J. Collier; Robert J. Ilcock; Adrian S. Meredith (New Zealand Journal of Marine and Freshwater Research, 1998)
Lowland streams in agricultural areas are often considered degraded because of high turbidity, high biomass of adventive macrophytes, and a predominance of fine bed substrates. Invertebrate faunas in these streams are being increasingly used in biomonitoring, and an understanding of factors affecting their distribution and abundance is important for interpreting the results of these studies. We measured physico‐chemical parameters and sampled macroinvertebrate faunas on inorganic substrates, wood, and macrophytes to investigate factors influencing invertebrate distribution and abundance in Waikato, New Zealand, lowland streams, and to evaluate six biotic indices and a rapid bioassessment protocol for lowland stream environments. At most sites, invertebrate faunas were dominated numerically on all substrate types by the hydrobiid snail Potamopyrgus antipodarum (Gray), the eusirid amphipod Paracalliope , and Diptera (mostly the chironomid Neonella forsythii Boothroyd and the blackfly Austrosimulium spp.). Stepwise regression analyses indicated that densities of some common taxa on inorganic substrates (0.1 m ‐2 ) and macrophytes (g ‐1 wet weight) were correlated with combinations of reach water depth, percentage of bed covered by macrophytes or sand/silt, and water quality factors including conductivity, water temperature, and measures of dissolved oxygen (DO) concentration and magnitude of diel fluctuation. These factors and also the amount of wood present explained 36–87% of the variation in several of the biotic indices examined on different substrate types. Some taxonomic (no. of taxa) and compositional (% dominant taxon) indices appeared sensitive to measured habitat conditions, and this may affect their utility for detecting water quality impacts in lowland streams. Percent Ephemerop‐tera, Plecoptera, and Tricoptera (EPT), and the Macroinvertebrate Community Index (MCI) and its quantitative analogue (QMCI) reflected factors thought to be more associated with direct and indirect effects of riparian and catchment land use on water quality (DO, conductivity, temperature, macrophyte cover). Comparison of indices derived from intensive and rapid bioassessment sampling yielded significant regressions with slopes that were not significantly different to 1 for % EPT and MCI. These indices appear to be particularly useful for rapid bioassessment of lowland stream environments.

Habitat and Avifaunal Recovery from Livestock Grazing in a Riparian Meadow System of the Northwestern Great Basin - David S. Dobkin; Adam C. Rich; William H. Pyle (Conservation Biology, 1998)

Outplanting and Differential Source Population Success in Lupinus guadalupensis - Kaius Helenurm (Conservation Biology, 1998)

Arbitrary and Capricious Species Conservation - John G. Sidle (Conservation Biology, 1998)

DNA Fingerprint Variation and Reproductive Fitness in the Plain Pigeon - Deshea L. Young; Marc W. Allard; Jorge A. Moreno; Michael M. Miyamoto; Carlos R. Ruiz; Raul A. Perez-Rivera (Conservation Biology, 1998)

Species Redundancy and Ecosystem Reliability - Shahid Naeem (Conservation Biology, 1998)

Mitigation of Habitat "Take" and the Core Area Concept - Joseph B. Buchanan; Richard J. Fredrickson; D. Erran Seaman (Conservation Biology, 1998)

Witness to Mass Extinction - Lauren J. Chapman; Mark W. Miller; Joan L. Walker; T. R. McClanahan; Diethart Matthies; Philip Cafaro (Conservation Biology, 1998)

Empirical Evaluation of a Test for Identifying Recently Bottlenecked Populations from Allele Frequency Data - Gordon Luikart; Jean-Marie Cornuet (Conservation Biology, 1998)

Strategies for Land-Bird Conservation on Mauritius - R. J. Safford; C. G. Jones (Conservation Biology, 1998)

Erratum (Conservation Biology, 1998)

The Potential Consequences of Pollinator Declines on the Conservation of Biodiversity and Stability of Food Crop Yields (Conservation Biology, 1998)

Evolutionary Distinctiveness and Status of the Endangered Lake Eacham Rainbowfish (Melanotaenia eachamensis) - Danqing Zhu; Sandie Degnan; Craig Moritz (Conservation Biology, 1998)

Viability of Sacramento River Winter-Run Chinook Salmon - Louis W. Botsford; John G. Brittnacher (Conservation Biology, 1998)

Forestry Trees as Invasive Aliens - David M. Richardson (Conservation Biology, 1998)

Response of Avian Communities to Disturbance by an Exotic Insect in Spruce-Fir Forests of the Southern Appalachians - Kerry N. Rabenold; Peter T. Fauth; Bradley W. Goodner; Jennifer A. Sadowski; Patricia G. Parker (Conservation Biology, 1998)

Natural Forest Management and Conservation of Biodiversity in Tropical Forests - Kamaljit S. Bawa; Reinmar Seidler (Conservation Biology, 1998)

Mitigation of Habitat “Take” and the Core Area Concept - Joseph B. Buchanan; Richard J. Fredrickson; D. Erran Seaman (Conservation Biology, 1998)

Empirical Evaluation of a Test for Identifying Recently Bottlenecked Populations from Allele Frequency Data - Gordon Luikart; Jean‐Marie Cornuet (Conservation Biology, 1998)

The Potential Consequences of Pollinator Declines on the Conservation of Biodiversity and Stability of Food Crop Yields (Conservation Biology, 1998)
Gordon Allen‐Wardell, BeeMaster, Inc., 1665, E. 18th St., #209, Tucson, AZ 85719, U.S.A. Peter Bernhardt, Department of Biology, St. Louis University, 3507, LaClede, St. Louis, MO 63101‐2010, U.S.A. Ron Bitner, International Pollination Systems, 16645, Plum Rd., Caldwell, ID 83605, U.S.A. Alberto Burquez, Instituto de Ecologia, Unam, Apartado Postal Hermosilo, Sonora 83000, Mexico Stephen Buchmann, USDA/ARS, 2000, E. Allen Rd., Tucson, AZ 85719, U.S.A. James Cane, USDA/ARS Bee Biology and Systematics Lab, Utah State University, Logan, UT 84322‐5310, U.S.A. Paul Allen Cox, National Tropical Botanical Garden, P.O. Box Lawai, Kauai, HI 96765, U.S.A. Virginia Dalton, Science Department, Pima College West, Desert Vista, 5901, South Calle Santa Cruz, Tucson, AZ 85709‐6000, U.S.A. Peter Feinsinger, Department of Biology, Northern University University, 5315, N. Copeland, Flagstaff, AZ 86004, U.S.A. Mrill Ingram, Arizona‐Sonora Desert Museum, 2101, North Kinney Road, Tucson, AZ 85743, U.S.A. David Inouye, Department of Sustainable Development, Conservation Biology, University of Maryland, College Park, MD 20742, U.S.A. C. Eugene Jones, Department of Biological Services, California State University at Fullerton, Fullerton, CA 92813, U.S.A. Kathryn Kennedy, U.S. Fish, Wildlife Service, 17011, Burnet Rd., Suite 200, Austin, TX 78716, U.S.A. Peter Kevan, Department of Environmental Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada Harold Koopowitz, Department of Biology, University of California, Irvine, CA 92717, U.S.A. Rodrigo Medellin, Instituto de Ecologia, Unam, Ciudad Universitaria, Apartado Postal 70‐275 D.F., 04510, Mexico Sergio Medellin‐Morales, Terra Nostra, Apartado Postal Victoria, Tamaulipas 887040, Mexico Gary, Paul Nabhan, Arizona‐Sonora Desert Museum, 2021, North Kinney, Tucson, AZ 85743, U.S.A. Bruce Pavlik, Department of Biology, Mills College, Oakland, CA 94610, U.S.A. Vincent Tepedino, USDA/ARS, Bee Biology and Systematics Lab., Utah State Univesity, Logan, UT 84322‐5310, U.S.A. Phillip Torchio, USDA/ARS, Bee Biology and Systematics Lab., Utah State University, Logan, UT 84321, U. S. A. Steve Walker, Bat Conservation International, 500 North Capital of Texas Highway, Austin, TX, U.S.A. Endorsers: Arizona‐Sonora Desert Museum, Bat Conservation International, Committee for Sustainable Agriculture, Community Alliance with Family Farmers, International Pollination Systems, Maine Organic Farmers and Gardeners Association, National Wildflower Research Center, Seacology Foundation, Society for Conservation Biology, Society for Ecological Restoration, Sonoran Arthropod Studies Institute, Terra Nostra, A.C., University of Maryland Department of Sustainable Development and Conservation Biology In a continuing effort to address contemporary conservation issues in a scholarly and rigorous fashion, the Board of Governors of the Society for Conservation Biology in 1997 approved a process by which a series of Commissioned Papers will be developed and published. Drawing on the Articles of Incorporation of SCB, which charge the Society to “disseminate scientific, technical, and management information through meetings, publications, and other media” and to “advance and articulate the Society’s position on matters of public policy,” this process is intended to formulate SCB positions on difficult issues relevant to the scientific basis for conservation. Those positions are made clear and explicit through publication of Commissioned Papers in this journal and may be used by the Society officers, Board of Governors, and members to guide activities of the society, synthesize and communicate the findings of conservation biology to the interested public, and inform decision makers of the Society’s scientific insights into issues relevant to public policy. The authority for such papers arises from the bylaws of the Society, which authorize the Policy and Resolutions Committee to develop “positions for the Society on issues related to conservation biology or policy issues where the scientific or management expertise of the Society will be of value” and to adopt “a protocol for the development of position statements and position papers.” Details of the process by which such papers are developed and approved by the Society were published in the SCB newsletter of November 1997 (Vol. 4, No. 4) and should be sought for further details. In this, the first SCB Commissioned Paper, Gary Paul Nabhan and co‐authors address an emerging and critically important issue: worldwide pollinator declines and their possible consequences for biodiversity conservation and agricultural stability. We plan to follow this with several Commissioned Papers each year on a broad scope of topics in an ongoing effort to clearly formulate SCB positions and influence public policy. The President and Board of Governors welcome suggestions from members for appropriate topics and will seek member input in writing these papers. Following reports of dramatic declines in managed and feral honey bees from nearly every region of North America, scientists and resource managers from the U.S., Mexico, and Canada came together to review the quality of the evidence that honey bees as well as other pollinators are in long‐term decline and to consider the potential consequences of these losses on the conservation of biodiversity and the stability of the yield of food crops. These experts in pollination ecology confirmed that the last 5 years of losses of honeybee colonies in North America leave us with fewer managed pollinators than at any time in the last 50 years and that the management and protection of wild pollinators is an issue of paramount importance to our food supply system. Although there are conclusive data that indicate 1200 wild vertebrate pollinators may be at risk, data on the status of most invertebrate species that act as pollination agents is lacking. The recommendations from a working group of over 20 field scientists, presented here, have been endorsed by 14 conservation and sustainable agriculture organizations, research institutes, and professional societies, including the Society for Conservation Biology. Among the most critical priorities for future research and conservation of pollinator species are (1) increased attention to invertebrate systematics, monitoring, and reintroduction as part of critical habitat management and restoration plans; (2) multi‐year assessments of the lethal and sublethal effects of pesticides, herbicides, and habitat fragmentation on wild pollinator populations in and near croplands; (3) inclusion of the monitoring of seed and fruit set and floral visitation rates in endangered plant management and recovery plans; (4) inclusion of habitat needs for critically‐important pollinators in the critical habitat designations for endangered plants; (5) identification and protection of floral reserves near roost sites along the “nectar corridors” of threatened migratory pollinators; and (6) investment in the restoration and management of a diversity of pollinators and their habitats adjacent to croplands in order to stabilize or improve crop yields. The work group encourages increased education and training to ensure that both the lay public and resource managers understand that pollination is one of the most important ecological services provided to agriculture through the responsible management and protection of wildland habitats and their populations of pollen‐vectoring animals and nectar‐producing plants. Consecuencias Potenciales de la Disminución de Polinizadores en la Conservación de la Biodiversidad y la Estabilidad en la Producción de Cosechas de Alimentos Debido a los constantes reportes de disminuciones dramáticas de abejas productoras de miel tanto manejadas como silvestres en casi todas las regiones de Norteamérica, científicos y manejadores de recursos de Estados Unidos, México y Canada se reunieron para revisar la calidad de las evidencias de que las abejas, así como otros polinizadores se encuentran en una disminución a largo plazo y para considerer las consecuencias potenciales de estas pérdidas en la conservación de la biodiversidad y la estabilidad de las cosechas de alimentos. Estos expertos en ecología de la polinización confirmaron que los últimos cinco años de pérdidas de colonias de abejas en Norteamérica nos ubican con menos polinizadores manejados que en ningún otro momento en los últimos 50 años y que el manejo y protección de polinizadores silvestres es un aspecto de suma importancia para nuestro sistema de abastecimiento de alimentos. A pesar de que existen datos concluyentes que indican que 1200 polinizadores vertebrados silvestres podrían encontrarse en riesgo, se carece de datos sobre la situación de la mayoría de las especies de invertebrados que actúan como polinizadores. Las recomendaciones de un grupo de trabajo de mas de 20 científicos, presentadas aquí, han sido respaldadas por 14 organizaciones de conservación y agricultura sustentable, institutos de investigación y sociedades de profesionistas incluyendo la Sociedad para la Biología de la Conservación. Entre las prioridades mas críticas de investigación y conservación de especies de polinizadores se encuentran; 1) incrementar el enfoque en sistemática de invertebrados, monitoreo y reintroducción como parte del manejo de hábitat crítico y planes de restauración; 2) evaluaciones de varios años de los efectos letales y subletales de pesticidas, herbicidas y la fragmentación del hábitat en las poblaciones silvestres de polinizadores dentro y alrededor de las tierras de cosechas; 3) inclusión del monitoreo de semillas y frutas y las tasas de visita en los planes de manejo y recuperación de plantas; 4) inclusión de las necesidades de hábitat para polinizadores críticamente importates en las designaciones de hábitat crítico para plantas amenazadas; 5) identificatión y protección de reservas florales cerca de sitios de percha a lo largo de “corredores de nectar” de polinizadores migratorios amenazados; y 6) inversión en la investigación y manejo de una diversidad de polinizadores y sus hábitats adyacentes a sitios con cosechas para poder estabilizar e improvisar la produccion de las cosechas. El grupo de trabajo hace un llamado para estimular un incremento en educación y entrenamiento para asegurar que tanto el público como los manejadores de recursos entiendan que la polinización es uno de los servicios ecológicos mas importantes aportados a la agricultura a través del manejo responsable y la protección de hábitats silvestres y de sus poblaciones de animales vectores de polen y plantas productoras de nectar.

Viability of Sacramento River Winter‐Run Chinook Salmon - Louis W. Botsford; John G. Brittnacher (Conservation Biology, 1998)
The winter run of chinook salmon (Oncorhynchus tshawytscha) on the Sacramento River in California (U.S.A.) was the first Pacific salmon stock to be listed under the U.S. Endangered Species Act. We describe some of the characteristics of Pacific salmon populations that require special consideration in viability analysis during development of a model specific to the Sacramento River winter run of chinook salmon. Their anadromous, semelparous life history leads to a special definition of quasi‐extinction. Random variability occurs primarily in spawning or early life and is reflected in the “cohort replacement rate,” the number of future spawners produced by each spawner, a measure consistent with the common practice of characterizing salmon population dynamics in terms of stock‐recruitment relationships. We determine the distribution of cohort replacement rates from spawning abundance data and life‐history information. We then show through simulations that replacing this distribution with a lognormal distribution with the same mean and variance has a negligible effect on extinction rates, but that approximating an indeterminate semelparous life history using a determinate semelparous life history leads to inaccurate estimates of extinction rate. We derive delisting criteria that directly assess the effects of habitat improvement by explicitly including population growth rate (geometric mean cohort replacement rate ≥1.0) in addition to abundance (≥10,000 female spawners). These delisting criteria allow for the uncertainty due to limited accuracy in measuring spawner abundance and the finite number of samples used to estimate population growth rate (estimates must be based on at least 13 years of data, assuming spawner abundance is measured with less than 25% error). Because the probability of extinction will generally be very sensitive to the uncertainty involved in meeting delisting criteria, we recommend that similar uncertainty be accounted for in future recovery criteria for all endangered species. Viabilidad del Salmón Chinook Durante la Corrida Invernal en el Río Sacramento La corrida invernal del salmón Chinook (Oncorhynchus tshawytscha) en Río Sacramento en California (E.U.A.) fue la primera población de salmón del pacífico que se incluyó en el Acta de Especies En Peligro de los Estados Unidos. Describimos algunas características de las poblaciones de salmón del Pacifico que requieren ser consideradas en el análisis de viabilidad al desarrollar un modelo específico para la corrida invernal del salmón Chinook en el Río Sacramento. Su historia de vida anádroma, semélpara conduce a una definición especial de la cuasi‐extinción. Principalmente durante el desove o en las primeras etapas de la vida ocurre variabilidad aleatoria que se refleja en la “tasa de reemplazo de cohorte,” el número de reproductores producidos por cada reproductor, que es un medida consistente con la práctica común de caracterizar a la dinámica de las poblaciones de salmón en términos de las relaciones de reclutamiento. Determinamos la distribución de tasas de reemplazo de cohortes a partir de datos de abundancia de reproductores e información de la historia de vida. Mediante simulaciones posteriormente mostramos que el cambio de esta distribución por una distribución logarítmica con la misma media y varianza tiene un efecto no significativo sobre las tasas de extinción, pero que la aproximación a una historia de vida semélpara indeterminada mediante una historia de vida semélpara determinada conduce a estimaciones inexactas de la tasa de extinción. Derivamos criterios para retirar de la lista de especies en peligro que directament evalúan los efectos del mejoramiento del hábitat al explícitamente incluir la tasa de crecimiento poblacional (media geométrica de las tasa de reemplazo de cohorte ≥ 1.0) además de la abundancia (≥10,000 hembras reproductoras). Estos criterios permiten la incertidumbre debido a la limitada precisión para medir la abundancia de reproductores y al número finito de muestras utilizadas para estimar la tasa de crecimiento (las estimaciones deben basarse en datos de por lo menos 13 años, suponiendo que la abundancia de reproductores se mide con

Modeling the Sustainability of Subsistence Farming and Hunting in the Ituri Forest of Zaire - David S. Wilkie; Bryan Curran; Richard Tshombe; Gilda A. Morelli (Conservation Biology, 1998)
We used empirical data to simulate the impacts, over the next 40 years, of subsistence‐level agricultural clearing and bushmeat consumption on forest resources within the recently established Okapi Wildlife Reserve in northeastern Zaire. Satellite imagery, human population census data, and field measurements were used to calculate present and projected impacts of agricultural clearing on forest cover. Data on per capita meat consumption and the species captured by hunters were combined with relevant ecological data to estimate ratios of consumption to production and to assess the sustainability of hunting. Even with projected population growth of nearly 300% among local communities over 40 years, sufficient secondary forest is available that agricultural clearing will have minimal effect on mature forest throughout most of the reserve. Impacts on the reserve’s fauna will be more dramatic, particularly within 15 km of villages, where most hunting currently occurs. Subsistence exploitation of forest antelopes may be sustainable in much of the reserve (especially if high estimates of game production are used), but as the human population continues to increase duikers will likely be over‐hunted. Primate populations do not appear to be threatened in the near future in those areas where bow hunters exploit monkeys, but an increase in this specialized activity in other regions of the reserve and growing human populations could change this. Although additional surveys of commonly hunted species throughout the Okapi Wildlife Reserve are essential to enhancing the precision of the simulation, our results suggest that mitigation efforts should be designed and implemented now if the long‐term effects of domestic bushmeat consumption are to be addressed. Modelado de la Sustentabilidad de Cosecha y Caza de Subsistencia en el Bosque Ituri en Zaire Utilizamos datos empíricos para simular los impactos del nivel de persistencia de clareo agricultural y el consumo de carne silvestre en los recursos forestales durante los próximos 40 años, dentro de la recientemente establecida reserva de vida silvestre Okapi en el noreste de Zaire. Imágenes de satélite, datos de censos poblacionales humanos y mediciones de campo fueron usados para calcular los impactos actuales y proyectados del clareo agricultural en la cobertura del bosque. Datos de consumo de carne per cápita y de las especies capturadas por caza fueron combinados con datos ecológicos relevantes para estimar la relación del consumo con la producción y para evaluar la sustentabilidad de la caza. Aún con el crecimiento poblacional proyectado de cerca de un 300% a lo largo de 40 años entre las comunidades locales, existe suficiente bosque secundario viable de tal manera que el clareo agricultural tendrá efectos mínimos sobre el bosque maduro a lo largo de la mayoría de la reserva. Impactos en la fauna de la reserva serán mas dramáticos, particularmente dentro de los 15 km de villas, donde la mayorá de la caza se lleva a cabo actualmente. La explotación de subsistencia de antílopes del bosque podría ser sustentable en gran parte de la reserva (especialmente si se utilizan estimaciones de producción cinegética), pero en vista de que la población humana continúa incrementando, algunos antílopes podrían ser sobre‐cazados. Las poblaciones de primates no parecen estar amenazadas a corto plazo en aquellas áreas donde los cazadores con arco capturan los monos, pero un incremento en esta actividad especializada en otras regiones de la reserva, aunado al crecimiento poblacional humano podría cambiar esta situación. Aunque estudios adicionales sobre las especies comunmente cazadas en la reserva Okapi son escenciales para incrementar la precisión de la simulación, nuestros resultados sugieren que los esfuerzos de mitigación deberán ser diseñados e implementados ahora si es que se pretenden abordar los impactos a largo plazo del consumo de carne silvestre.

Rationale for a System of International Reserves for the Open Ocean - Claudia E. Mills; James T. Carlton (Conservation Biology, 1998)

Residual Patches and their Contribution to Forest‐Bird Diversity on Northern Minnesota Aspen Clearcuts - Samuel B. Merrill; Francesca J. Cuthbert; Gary Oehlert (Conservation Biology, 1998)
Managers of upland forest generally operate with the assumption that leaving residual timber in clearcuts is beneficial for wildlife. Our primary objective in this study was to evaluate the contribution of residual patches to forest birds by (1) characterizing differences in components of bird diversity between clearcuts with and without residual patches, (2) characterizing differences in components of bird diversity between residual patches and clearcut edges, and (3) describing any clearcut‐wide effects of residual patches for any bird species or group. Breeding birds were surveyed in 40 aspen clearcuts (20 clearcuts with and 20 clearcuts without residual patches) 3–9 years old from May to July 1993 in northern Minnesota. Sixteen additional survey points were established, eight each in clearcut edge and in clearcuts with residual patches but with the survey point outside the residual patch. Two diversity indices, four avian nesting guilds, and 12 bird species showed significant differences between treatments when analyzed with multiple regression analysis and analysis of variance. Five of the seven species significantly associated with residual patches are of high regional management concern: Veery (Catharus fuscescens), Ovenbird (Seiurus aurocapillus), Rose‐breasted Grosbeak (Phucticus ludovicianus), Canada Warbler (Wilsonia canadensis), and Black‐throated Green Warbler (Dendroica virens). Results from this study suggest that residual patches contribute to forest‐bird diversity in northern Minnesota aspen clearcuts, and may enhance bird populations on regional and landscape scales. Las Reservas Forestales y su Contribución a la Diversidad de la Avifauna del Bosque en Matarrasas de Álamos del Norte de Minnesota Los administradores de bosques de altura generalmente postulan la idea de que el dejar pequeñas reservas forestales en zona de tala es beneficioso para la vida silvestre. El objetivo principal de este estudio fue el de evaluar la contribución de las reservas forestales a la diversidad de la avifauna del bosque. Esto se llevó a cabo mediante (1) Caracterización de los componentes de la diversidad de la avifauna con y sin áreas de reservas forestales; (2) Caracterización de las diferencias de los componentes de la avifauna entre áreas de reserva y de tala; (3) Descubrir los efectos que tiene la tala de las áreas de reserva en las especies de aves o grupos de aves. Aves en reproducción fueron estudiadas en el norte de Minnesota en 40 parcelas de tala de álamos 3 a 9 años de edad (20 en zonas con reservas y 20 en zonas sin reservas) durante los meses de mayo a julio de 1993. Deiciséis parcelas de estudios fueron establecidos, 8 en zonas de tala sin reservas y 8 en zonas de tala con reservas, pero con puntos de observación fuera de la zona de reserva. Diferencias significativas entre tratamientos se encontraron mediante Análisis de Regresión Múltiples y Análisis de Varianza (ANOVA) utilizando dos índices de diversidad, cuatro grupos de la avifauna anidando y 12 especies de aves. Se encontró que cinco de las siete especies de la avifauna asociadas a las áreas de reserva son consideradas con mucha necesidad de manejo regional: Veery (Catharus fuscescens), Ovenbird (Seiurus aurocapillus), Rose‐breasted Grosbeak (Phucticus ludovicianus), Canada Warbler (Wilsonia canadensis), and Black‐throated Green Warbler (Dendroica virens). Los resultados de este estudio sugieren que las reservas forestales representan una contribución valiosa a la diversidad de la avifauna del bosque en la zona de tala de álamos del norte de Minnesota y puede que tengan una gran influencia sobre la población de aves a escala regional y de paisaje.

Witness to Mass Extinction - Lauren J. Chapman; Mark W. Miller; Joan L. Walker; T. R. McClanahan; Diethart Matthies; Philip Cafaro (Conservation Biology, 1998)

Evolutionary Distinctiveness and Status of the Endangered Lake Eacham Rainbowfish ( Melanotaenia eachamensis ) - Danqing Zhu; Sandie Degnan; Craig Moritz (Conservation Biology, 1998)
The Lake Eacham rainbowfish (Melanotaenia eachamensis) was declared extinct in the wild in the late 1980s after it disappeared from its only known locality, an isolated crater lake in northeast Queensland. Doubts have been raised about whether this taxon is distinct from surrounding populations of the eastern rainbowfish (Melanotaenia splendida splendida). We examined the evolutionary distinctiveness of M. eachamensis, obtained from captive stocks, relative to M. s. splendida through analysis of variation in mtDNA sequences, nuclear microsatellites, and morphometric characters. Captive M. eachamensis had mtDNAs that were highly divergent from those in most populations of M. s. splendida. A broader geographic survey using RFLPs revealed some populations, initially identified as M. s. splendida, that carried eachamensis mtDNA, whereas some others had mixtures of eachamensis and splendida mtDNA. The presence of eachamensis‐like mtDNA in these populations could in principle be due to (1) sorting of ancestral polymorphisms, (2) introgression of M. eachamensis mtDNA into M. s. splendida, or (3) incorrect species boundaries, such that some populations currently assigned to M. s. splendida are M. eachamensis or are mixtures of the two species. These alternative hypotheses were evaluated through comparisons of four nuclear microsatellite loci and morphometrics and meristics. In analyses of both data sets, populations of M. s. splendida with eachamensis mtDNA were more similar to captive M. eachamensis than to M. s. splendida with splendida mtDNA, supporting hypothesis 3. These results are significant for the management of M. eachamensis in several respects. First, the combined molecular and morphological evidence indicates that M. eachamensis is a distinct species and a discrete evolutionarily significant unit worthy of conservation effort. Second, it appears that the species boundary between M. eachamensis and M. s. splendida has been misdiagnosed, such that there are extant populations on the Atherton Tableland as well as areas where both forms coexist. Accordingly, we suggest that M. eachamensis be listed as vulnerable, rather than critical (or extinct in the wild). Third, the discovery of extant but genetically divergent populations of M. eachamensis on the Atherton Tableland broadens the options for future reintroductions to Lake Eacham. Distintividad Evolutiva y Estatus del Amenazado Pez Arcoíris ( Melanotaenia eachamensis ) del lago Eacham El pez acoíris del lago Eacham (Melanotaenia eachamensis) fue declarado extinto de poblaciones silvestres a finales de los 80’s después de su desaparición de la única localidad conocida, un cráter aislado en el noreste de Queensland. Se han incrementado las dudas acerca de si este taxón es distinto de las poblaciones circunvecinas del pez arcoiris del este (Melanotaenia spendida splendida). Examinamos la difernciación evolutiva de M. eachamensis, obtenida de stocks cautivos, en relación con M. s. splendida mediante un análisis de variación en secuencias de ADNmt, nuclear, microsatélites y caracteres morfométricos. M. eachamensis cautivos tuvieron ADNmt que difirió grandemente de aquellos provenientes de la mayoría de las poblaciones de M. s. splendida. Un estudio geográfico mas amplio usando RFLPs reveló que algunas poblaciones inicialmente identificados como M. s. splendida, contenían ADNmt de eachamensis, mientras que otros presentaron mezclas de DNAmt de eachamensis y splendida. La presencia de DNAmt del tipo de eachamensis en estas poblaciones, podría en principio, deberse a 1) una forma de polimorfismos ancestrales, 2) Introgresión del ADNmt de M. eachamensis hacia M. s. splendida o 3) límites incorrectos para las especies, tal como que algunas poblaciones actualmente asignadas al ADNmt de M. s. splendida son M. eachamensis o son una mezcla de las dos especies. Estas hipótesis alternativas fueron evaluadas mediante comparaciones de cuatro loci microsatélites nucleares y datos morfométricos y merísticos. En el análisis de ambas bases de datos, las poblaciones de M. s. splendida con DNAmt de M. eachamensis fueron mas similares a M. eachamensis cautivos que a M. s. splendida con ADNmt de splendida, esto soporta la hipótesis 3. Estos resultados son significativos para el manejo de M. eachamensis en diversos aspectos. Primero, las evidencias moleculares y morfológicas indican que M. eachamensis es una especie distintiva y una unidad evolutiva significante, lo suficientemente valiosa como para un esfuerzo conservacionista. Segundo, si parece que los limites de especies entre M. eachamensis y M. s. splendida han sido mal diagnosticados, a tal grado que hay poblaciones existentes en el altiplano de Atherton, asi como en áreas donde ambas formas coexisten. De acuerdo con esto, sugerimos que M. eachamensis debe ser enlistada como vulnerable, en lugar de crítica (o extinta). Tercero, el descubrimiento de poblaciones existentes, pero genéricamente divergentes de M. eachamensis en el altiplano de Atherton amplía las opciones para futuras reintroducciones en el lago Eacham. X775047

Zoning of Timber Extraction in the Brazilian Amazon - Adalberto Veríssimo; Carlos Souza Júnior; Steve Stone; Christopher Uhl (Conservation Biology, 1998)
The state of Pará (1,248,042 km 2 ), in eastern Amazônia, produces 65% of Brazil’s roundwood. Logging is now spreading across this state in an unplanned and unregulated fashion. Using a geographic information system (GIS), we combined and analyzed spatial information on forest cover, legal land classification, log processing industries, biodiversity, and infrastructure for the entire state. We first used this GIS, in combination with economic data, to analyze the spread of logging activities in Pará. We found that in the mid‐1990s, the potential already existed (in economic terms) to harvest timber from 80% of Pará’s forested lands: 21% of Pará’s forest was accessible for the harvest of all commercial species, including those of low value; an additional 30% was accessible for logging a select group of medium‐value species; and a final 29% of the state’s forest was accessible for the logging of mahogany, a high‐value species. Although 29% of Pará’s lands are legally protected from logging, protection is weak: almost three‐quarters of these “protected” lands fall within the zone in which timber can now be profitably harvested. We also used the GIS to develop a rationale for zoning where logging might be permitted, as well as prohibited, in Pará. First, we noted that 19% of the state contained lands without timber (12% deforested, 6.3% nonforest vegetation types, and 0.7% water). The land that we designate for logging, based both on economic and conservation considerations, would be approximately 32% (400,000 km 2 ) of the state. This would include areas where logging is already underway (24%), production reserves and buffer areas (3%), and remote areas with no conservation restrictions (5%). We propose that the remaining area (49%, or 611,540 km 2 ) be protected from logging, at least for the time being. These lands include forested areas where logging is already “officially” prohibited (28% of Pará) as well as nonprotected areas with a high conservation priority (21%) (i.e., areas that are especially rich in biodiversity). Zonación de la Extracción de Madera en la Amazonia Brasileña El estado de Pará (1,248,042 km 2 ), en el este de la amazonia produce 65% de la madera redonda del Brazil. La tala se esta dispersando actualmente a lo largo de este estado sin planificación ni regulación. Usando un Sistema de Información Georgráfico (GIS), combinamous y analizamos información espacial de cobertura forestal, clasificación legal de la tierra, industrias procesadoras de troncos, biodiversidad e infraestructura para la totalidad del estado. Primero utilizamos este GIS en combinación con datos económicos para analizar la dispersión de las actividades de tala en Pará. Encontramos que a mediados de los 90’s el potencial ya existía (en terminos económicos) para cosechar madera en 80% de las tierras forestales de Pará: 21% del bosque de Pará era accesible para la cosecha de todas las especies comerciales, incluyendo aquellas de bajo valor; un adicional 30% era accesible para tala de un grupo selecto de especies de mediano valor y un final 29% del bosque estatal era accesible para la tala de cahoba‐especie de alto valor comercial. Aunque un 29% de las tierras de Pará estan legalmente protegidas contra la tala, la protección es débil; casi tres cuartas partes de estas tierras “protegidas” se encuentran de la zona en que la madera puede ser ahora cosechada de manera rentable. También utilizamos GIS para desarrollar los fundamentos para una zonación donde la tala podría ser permitida, así como prohibida, en Pará. Primero, notamos que 19% del estado contiene tierras sin madera (12% deforestado, 6.3% tipos de vegetación no forestal y 0.7% es agua). La tierra que asignamos para tala, en base a consideraciones tanto económicas como de conservación, sería de aproximadamente 32% (400,000 km 2 ) del estado. Esto incluye áreas donde la tala se encuentra actualmente en camino (24%), áreas de producción de reserva y áreas amortiguadoras (3%) y áreas remotas sin restricciones de conservación (5%). Proponemos que el área restante (49% ó 611,540 km 2 ) sea protegida de la tala, al menos por un tiempo inmediato. Estas tierras incluyen áreas boscosas donde la tala es actualmente prohibida “oficialmente” (28% de Pará). Asi como áreas no protegidas con un alta priridad de conservación (21%) (i.e. áreas que son especialmente ricas en biodiversidad).

Interactive Keys, Inventory, and Conservation - James K. Jarvie; P. F. Stevens (Conservation Biology, 1998)

DNA Fingerprint Variation and Reproductive Fitness in the Plain Pigeon - Deshea L. Young; Marc W. Allard; Jorge A. Moreno; Michael M. Miyamoto; Carlos R. Ruiz; Raul A. Pérez‐Rivera (Conservation Biology, 1998)

Outplanting and Differential Source Population Success in Lupinus guadalupensis - Kaius Helenurm (Conservation Biology, 1998)
The choice of appropriate source populations is crucial for the success of outplanting attempts, but this choice is often based on assumptions regarding patterns of adaptation and distribution of genetic variability in natural populations. Although local adaptation is often assumed to exist, few data exist to support this model on smaller geographic scales, particularly in rare plant species. My study investigated the pattern of adaptation in populations of an annual, island endemic plant, Lupinus guadalupensis, on San Clemente Island, California. A reciprocal transplant experiment with three populations provided no evidence for local adaptation, but two source populations performed significantly better than the other at all sites. Desiccation and herbivory are the major factors causing mortality and reducing fruit production. The young rosettes are the most vulnerable life‐cycle stage. Differences among natural population sites in vegetation community, dominant species, soil type, and parent material did not affect populations of L. guadalupensis; significant differences were not observed in either total fruit production or in the majority of fitness components. Success of outplanting into three introduction sites varied from the death of all plants before flowering or before fruits ripened to fruit production exceeding that at natural population sites. The results suggest that large populations are better sources of seeds for outplanting in L. guadalupensis and that outplanting is most successful in sites where plants are least subject to desiccation. Siembra en Sitios Externos y Fuentes Diferenciales de Exito Poblacional en Lupinus guadalupensis La detección de fuentes apropiadas de poblaciones es crucial para el éxito de los intentos de siembra externa, pero esta opción se basa frecuentemente en suposiciones sobre patrones de adaptación y distribución de variabilidad genética en poblaciones naturales. A pesar de que frecuentemente se asume que la adaptación local existe, pocos datos soportan este modelo a escala geográfica pequeña, particularmente en especies raras de plantas. Investigué el patrón de adaptación en poblaciones de una planta anual endémica isleña, Lupinus guadalupensis, en la isla San Clemente, California. Un experimento de transplante recíproco con tres poblaciones, no aportó evidencia de adaptación local, pero dos poblaciones fuente se desarrollaron significativamente mejor que la otra en todos los sitios. La desecación y hervivoría son los factores mayores causantes de la mortalidad y reducción de la producción de frutos. Las rosetas jóvenes son los estados del ciclo de vida mas vulnerables. Diferencias entre sitios de poblaciones naturales en la comunidad de la vegetación, dominancia de especies, tipo de suelo y material parental no afectó las poblaciones de L. guadalupensis; no se observaron diferencias significativas en la producción total de frutos ni en la mayoría de los componentes del estado de las especies. El éxito de plantar en el exterior en tres sitios de introducción diferentes varió desde la muerte de todas las plantas antes de florecer hasta la muerte antes de que los frutos maduráran para producción, esto excedió los valores de sitios con poblaciones naturales. Los resultados sugieren que las poblaciones grandes son mejores fuentes de semillas para plantar L. guadalupensis en otros sitios y que el éxito de estas plantaciones es mayor en sitios donde las plantas son poco sujetas a la desecación.

A Forager‐Resource Population Ecology Model and Implications for Indigenous Conservation (Conservation Biology, 1997)

The Ultimate Tragedy of Commons - Charles E. Kay (Conservation Biology, 1997)

A New Approach to International Conservation News - Joshua Ginsberg (Conservation Biology, 1997)

The Failure of Universities to Produce Conservation Biologists - Reed F. Noss (Conservation Biology, 1997)

Stress Hormones and Radiocollaring of African Wild Dogs - Marion L. East; Heribert Hofer; Roger Burrows; Marion L. East (Conservation Biology, 1997)

Testing Species Boundaries in Biodiversity Studies - Jack W. Sites; Keith A. Crandall (Conservation Biology, 1997)
A paper recently published by reported a molecular genetic study of all recognized subspecies of the common snapping turtle ( Chelydra serpentina) and concluded from patterns of geographic variation in isozyme and mitochondrial DNA restriction fragment pattern data that three evolutionary species should be recognized in this group. We suggest that this paper is fundamentally flawed because it fails to present any species concept as a testable hypothesis. Data are collected in the absence of any conceptual framework for diagnosing species boundaries, so no criteria for acceptance or rejection of a preferred hypothesis are formulated, and species boundaries are determined in a nonrigorous, post hoc manner. Further, the absence of specific criteria for species diagnosis in this case leads to flaws in sampling design, data collection, and data analysis. Because these design flaws are typical of many studies, we briefly outline three different lineage‐based operational species concepts (phylogenetic, concordance, and cohesion) and present an alternative interpretation of the Chelydra data, insofar as this is possible given the design limitations. We conclude the following: (1) species status may not be warranted for the Central and South American taxa, (2) more‐detailed analysis is warranted in the U.S. population because distinct lineage may be obscured by poor lab technique or introgression of mtDNA, and (3) the Ecuadorean population may deserve species status based on fixed nuclear isozyme loci. We recommend the following procedures for implementation of lineage‐based species concepts within a rigorous hypothesis testing framework. First, if an animal is to be sacrificed, proper care should be taken to utilize different tissues for multiple pass electrophoresis. This will unmask hidden heterogeneity and maximize the number of resolved loci. Second, when phylogenetic relationships are reconstructed with restriction fragment length polymorphism data, fragment data should be converted to site data to avoid uncertainties in homology. Finally, a proper sampling scheme should be designed to address the question of species status in terms of numbers of individuals, genetic loci, populations, and geographic regions. Comprobar Demarcaciones de Especies en Investigaciones de Biodiversidad Un artículo publicado recientemente por , reportó un estudio acerca de la genética molecular en todos las subespecies reconocidos de la tortuga común ( Chelydra serpentina). Se concluyó, con base en los patrones de variación geográfica en isoenzimas y en fragmentos de restricción de ADN mitocondrial, que tres especies evolutivas deberían ser reconocidas en este grupo. Nosotros sugerimos que ese artículo está mal fundamentado porque no presenta un concepto de especie como hipótesis a probar. Por consiguiente, los datos son obtenidos en ausencia de un marco conceptual para diagnosticar límites de especies. Esto es, que no se formula un criterio para la aceptación o rechazo de una hipótesis adoptada y los límites de especie son determinados de una manera post hoc y no rigurosa. Además, la ausencia de criterios específicos para la diagnosis de especies, en este caso, lleva a un inadecuado diseño de muestreo, obtención de datos y análisis de los mismos. Debido a que estos diseños inadecuados son típicos en muchos estudios, nosotros damos brevemente los lineamientos de tres diferentes conceptos operacionales de especie basados en linajes ( filogenético, de concordancia y de cohesión) y presentamos una interpretación alternativa para los datos de Cheyldra, hasta donde es posible, dadas las limitaciones del diseño. Concluimos lo siguiente: (1) el estatus de especie puede no ser garantizado para los taxa de Centro y Suramérica, (2) un análisis más detallado es requerido en las poblaciones de U.S. ya que técnicas deficientes de laboratorio o la introgresión de mtADN pueden dificultar la distinción de linajes, y (3) las poblaciones ecuatorianas podrían recibir el estatus de especie con base en loci fijados de isoemzimas nucleares. Recomendamos lo siguiente para la implementación de conceptos de especie basados en linajes dentro de un riguroso marco de hipótesis a probar. Primero, si un animal va a ser sacrificado, se debe asegurar el uso de diferentes tejidos para múltiples corridas de electroforesis. Esto descubrirá heterogeneidad escondida y maximizará el número de loci resueltos. Segundo, al construir las relaciones filogenéticas con datos de polimorfismos en longitud de fragmentos de restricción, se debería de convertir los datos de fragmentos en datos de sitios para evitar dudas en la homología. Finalmente, se debería diseñar un apropiado esquema de muestreo para abordar la pregunta del estatus de especie en términos de número de individuos, loci genéticos, poblaciones y regiones geográficas.

Effects of Habitat Fragmentation on the Abundance of Two Species of Leptodactylid Frogs in an Andean Montane Forest - David M. Marsh; Peter B. Pearman (Conservation Biology, 1997)
We used visual transect surveys to study the effects of forest fragmentation on abundance of two species of Leptodactylid frogs in an Andean forest of northern Ecuador. We measured the abundances of Eleutherodactylus chloronatus and E. trepidotus at various distances from the forest edge in one large forest patch (200 ha) and four adjacent forest fragments (0.25–5.3 ha). We also collected data on forest characteristics ( leaf litter thickness, understory density, and number and size of canopy trees) at each site. Abundance of E. chloronatus and E. trepidotus were respectively 3.5 and 2.1 times higher at sites in the large forest patch than at sites in the small fragments. Abundance of E. chloronatus was positively correlated with the log of patch size and inversely correlated with understory density. E. trepidotus abundance was not correlated with either patch size or understory density, but was inversely correlated with distance from the site to the large forest patch. The two species thus both appear to be affected by habitat fragmentation, but through different processes. Efectos de la Fragmentación del Hábitat en la Abundancia de dos Especies de Ranas Leptodactílidas en un Bosque de Montaña de los Andes Utilizamos datos de transectos lineales para estudiar los efectos de la fragmentación del bosque sobre dos especies de ranas en los Andes del norte de Ecuador. Medimos la abundancia de Eleutherodactylus chloronatus y E. trepidotus en sitios a distancias determinadas del horde del hosque en un fragmento grande (200 ha) y cuatro fragmentos menores adyacentes (0.25–5.3 ha). Obtuvimos dates sobre las características del bosque (espesor de la hojarasca, densidad del sotobosque, número de árboles en el dosel) en cada sitio. La abundancia de E. chloronatus y E. trepidotus fue 3.5 y 2. 1 veces mas alta en los sitios del fragmento grande one en los sitios de los fragmentos menores. La abundancia de E. chloronatus estuvo correlacionada con el logaritmo del tamaño del fragmento e inversamente correlacionada con la densidad del sotobosque. La abundancia de E. trepidotus no estuvo correlacionada con el tamaño del fragmento, ni con la densidad del sotobosque, pero sí con la distancia del sitio hasta el fragmento grande. Po lo tanto, las dos especies aparentemente son sustancialmente impactadas por la fragmentación del hábitat, pero a través de procesos diferentes.

Linking Human Health to Biological Diversity - Manuel Cesario; Richard B. Norgaard; David R. Peart; Kamaljit S. Bawa; Thomas V. Dietsch (Conservation Biology, 1997)

The Theory of Conservation Biology - Kimberly A. With (Conservation Biology, 1997)

Near‐Extinction of Porcupines by Mountain Lions and Consequences of Ecosystem Change in the Great Basin Desert - Richard A. Sweitzer; Stephen H. Jenkins; Joel Berger (Conservation Biology, 1997)
In North America’s Great Basin Desert changes in plant communities that occurred after the introduction of domestic livestock in the late 1800s resulted in the irruption of mule deer (Ocodoileus hemionus) and expansion of mountain lions ( Felis concolor). We report on a situation in which mountain lion predation caused the near‐extinction of another native species, porcupines ( Erethizon dorsatum). We used demographic information collected over 8 years on an individually identified population and long term climatic data in a stochastic population model to examine the hypothesis that predation and not weather‐induced starvation or random population fluctuations threatened the persistence of a naturally small population of porcupines. Whether drought‐related reductions in mule deer densities induced mountain lions to prey on porcupines is unclear, but our results suggest predation and not climatic conditions caused the decline of a once robust population of over 80 to Cuasi‐extinción de Puercoespines por Pumas y Consecuencias del Cambio en el Ecosistema del Desierto Great Basin Los cambios ocurridos en las comunidades vegetales del Desierto Great Basin en Norteamérica después de la introducción de ganado a fines del siglo pasado resultaron en la irrupción del venado bura (Odocoileus hemionus) y en la ezpansión del puma ( Felis concolor). Este trabajo reporta un caso en el que la depredación por pumas casi causó la extinción de otra especie nativa, el puercoespín ( Erethizon dorsatum). Utilizamos información demográfica de una población individual obtenida a lo largo de 8 años así como datos climáticos de varios años en un modelo estocástico de la población para examinar la hipótesis de que la persistencia de poblaciones naturalmente pequeñas de puercoespines estaba amenazada por la depredación y no por hambruna ni por fluctuaciones poblacionales aleatorias. No es claro si la reducción en la densidad de venado bura asociada a períodos de sequía indujo a los pumas a depredar puercoespines, pero nuestros resultados sugieren que la depredación y no las condiciones climáticas, provocó la declinación de una población robusta de mas de 80 animales a menos de 5 en solo tres años. Estos datos representan un caso inusual en el que la depredación por una especie nativa casi causó la extinción de una especie‐presa nativa, lo que sugiere que una consecuencia no prevista de los cambios en los ecosistemas de Norteamérica occidental puede ser la inminente pérdida de poblaciones pequeñas de vertebrados nativos.

The Sustainability of the Indigenous Dugong Fishery in Torres Strait, Australia / Papua New Guinea - H. Marsh; A. N. M. Harris; I. R. Lawler (Conservation Biology, 1997)
The sustainability of the indigenous dugong ( Dugong dugon) fishery in Torres Strait is evaluated on the basis of aerial survey estimates of the size of the regional dugong population in 1987 and 1991 and a survey of catches of dugongs taken by local communities between 1991 and 1993. The estimate of the dugong population in the Torres Strait region in November‐December 1991 was 24,225 (± SE 3,276) compared with the corresponding estimate of 13,319 (± SE 2,136) for November 1987. The difference between the two estimates cannot be explained by natural increase of the population or variations in the sighting conditions encountered during the two aerial surveys. We believe this difference is due to a major redistribution of du‐gongs within the survey region or migration into Torres Strait, probably from Irian Jaya (Indonesia). Dugongs are a major component of the traditional fishery in Torres Strait. The biomass of dugongs landed between June 1991 and May 1993 was higher than the weight of any other component of the traditional catch. The estimated annual dugong catch of 1226 (± SE 204) was higher than previous catch estimates. It is impossible to verify the sustainability of this harvest without an understanding of the movements of the dugong population, better absolute estimates of dugong population size, dugong catch statistics for Papua New Guinea and adjacent regions in Australia, and current estimates of life history parameters for dugongs in Torres Strait, all of which will be difficult to obtain. The mean estimate of the annual dugong catch in Torres Strait for 1991–1993, however, is approximately 5% of the mean estimate of the dugong population size in 1991. This is too close to the estimated maximum rate of increase of the dugong population to be sustainable if the estimate of dugong numbers is close to an absolute estimate or if there is substantial emigration of dugongs from the area. Co‐management arrangements must be developed between the government agencies responsible for the dugong fishery and the Torres Strait Islanders in order to develop management strategies that will provide for the Islander’s traditional hunting expectations and maintain dugong numbers. Es Sostenible la Caza Actual de Dugones en el Estrecho de Torres La posibilidad de sostener la caza artesanal en el Estrecho de Torres es evaluado sobre la base de conteos aereos del número de la población de dugones ( Dugong dugon) en esta región en 1987 y 1991, y una encuesta de los dugones cazados por la comunidad local entre 1991 y 1993. La población estimada de dugones en la región del Estrecho de Torres durante el perìodo noviembre‐diciembre 1991 fue de 24,225 (± SE 3,276) animales, comparada con la población correspondiente estimada en noviembre de 1987, la cual fue de 13,319 (± SE 2,136) animales. La diferencia entre los dos estimados no puede explicarse como un aumento natural de población o variaciones en visibilidad encontradas durante los dos conteos aereos. Creemos que esta diferencia se debe mas bien a un gran cambio en la distribución de dugones en el área estudiada o a una migración de animales al Estrecho de Torres, probablemente desde Irian Jaya. El dugón es todavía un componente importante de la caza artesanal en el Estrecho de Torres. El peso húmedo de los dugones cazados entre junio 1991 y mayo 1993 fue superior a cualquier otro componente de la pesca artesanal. El estimado caza anual de du‐gones de 1,226 (± SE 204) fue superior a cualquier estimado anterior. Es imposible verificar si la caza tradicional de dugones es sostenible sin antes conocer los movimientos de la población, mejores estimados absolutos de la población de dugones y la estadìstica de la caza para Papua Nueva Guinea y regiones ayacentes en Australia, y los parámetros de ciclo de vida de los dugones en el Estrecho de Torres, ninguno de los cuales es fácil de obtener. Sin embargo, el estimado medio de la caza anual de dugones en el Estrecho de Torres durante el período de 1991‐93 es aproximadamente 5% del estimado medio de la población en 1991. Esta cifra está demasidada cerca a la taza máxima de incremento estimada de la población de dugones para ser sostenible si es que los esimados poblacionales están en realidad cerca a un estimado absoluto, o si existe una migración apreciable de dugones fuera del area. Hay que desarrolar arreglos de colaboración entre las entidades del gobierno responsables para la caza de los dugones y los isleños del Estrecho de Torres con el fin de desarrolar estratégias administrativas que tomarán en cuenta las expectativas de caza tradicional de los isleños y al mismo tiempo mantener la población de dugones.

Conservation Biology, Values, and Advocacy - Brent M. Matsuda (Conservation Biology, 1997)

Assessing the Data Requirements of Spatially Explicit Dispersal Models - Mary Ruckelshaus; Cynthia Hartway; Peter Kareiva (Conservation Biology, 1997)
We evaluated the consequences of parameter errors for predictions of spatially explicit population models. We examined a simple model for organisms dispersing in a fragmented landscape and assessed how errors in three model input parameters propagate into errors in model predictions: (1) misclassification of habitat suitability (landscape error); (2) incorrect estimation of how far a disperser can travel (mobility error); and (3) incorrect estimation of the mortality rate of dispersers (dispersal‐mortality error). The two‐dimensional landscape through which organisms dispersed was filled with patches of various shapes (square, linear, and elbow) and sizes (4, 9, and 16 cells), and we allowed the overall proportion of suitable habitat in the landscape (2, 8, 16, and 24%) to vary among runs. A single run consisted of 400 individuals dispersing through the landscape until they found suitable habitat patches, and the output was a frequency distribution of the number of steps taken before a patch was found (n = 400 individuals). In the error‐free model, dispersal success increased with the percentage of the landscape that was composed of suitable habitat and was greater in landscapes filled with more small patches than in those with fewer large patches. Errors in dispersal‐mortality parameters resulted in the greatest prediction errors (25–90%), followed by mobility errors (2–60%) and landscape errors ( Valoración de los Requerimientos de Datos para Modelos de Dispersión Espacialmente Explícita En este trabajo evaluamos las consecuencias de errores en los parámetros de las predicciones de modelos poblacionales con estructura espacial explícita. Construímos un modelo poblacional en el cual los organismos se dispersan en un ambiente fragmentado y evaluamos la propagación de errores en los parámetros usados en las predicciones que resultan del modelo. Nuestras simulaciones exploran las consecuencias de tres tipos de errores: (1) clasificación errónea del ambiente adecuado para la especie (error de “paisaje”); (2) estimación incorrecta de la distancia que puede viajar un organismo (error de movilidad); y (3) estimación incorrecta de la tasa de mortalidad de los organismos que se dispersan. El ambiente bi‐dimensional a través del cual los organismos se dispersan es ocupado por parches de distintas formas (cuadrados, lineales y acotados) y tamaños (4, 9 y 16 celdas); variamos además la proporción total de la superficie de ambiente adecuado (2, 8, 16, y 24%). Cada corrida del modelo consistió en 400 individuos dispersandose a través del ambiente hasta encontrar un parche adecuado. La distribución de frecuencias del número de pasos tomados antes de encontrar un parche apropiado (n = 400 individuos) fue evaluada para cada combinación de valores de los parámetros. El modelo libre de errores produjo simulaciones donde el éxito de dispersión aumentó con la proporción de ambiente adecuado y también en ambientes con muchos parches chicos comparado con aquellos con pocos parches grandes. Errores en la mortalidad de los individuos que se dispersan resultaron en los mayores errores de predicción (25–90%), seguido de errores en la movilidad de los individuos (2–60%) y errores en la calidad del hábitat (1–17%) en términos relativos. En general, los errores de predicción fueron mayores en ambientes con bajo porcentaje de hábitat adecuado, precisamente el tipo de ambiente característico de la mayoría de especies que concieren a los esfuerzos de conservación. Nuestros resultados señalan la importancia de la obtención de medidas empíricas de los errores asociados a los parámetros de dispersión y sugieren la necesidad de utilizar estrategias alternativas de modelado para predecir el destino de poblaciones que habian ambientes fragmentados.

A Recovery Program for the Natterjack Toad ( Bufo calamita ) in Britain - Jonathan S. Denton; Susan P. Hitchings; Trevor J. C. Beebee; Antony Gent (Conservation Biology, 1997)
The natterjack toad ( Bufo calamita) is an endangered species in Britain and has been legally protected since 1975. This amphibian suffered a major decline during the first half of the twentieth century, due partly to habitat destruction but mostly to successional changes in its specialized biotopes and anthropogenic acidification of breeding sites. In addition to site and species protection, extensive autecological research over the past 25 years has provided the foundations for an intensive, 3‐year species recovery program funded by the statutory nature conservation organizations (English Nature and the Countryside Council for Wales). This program was based on habitat management and reintroductions to restored sites and followed similar but less intensive efforts. Management of heath and dune habitats focused on restoration and maintenance of early stages of seral succession, initially through physical clearance of invasive scrub and woodland vegetation and later by the reestablishment of grazing regimes similar to those prevalent in earlier centuries. In some cases extra breeding pools were provided to either increase or stabilize natterjack toad populations that had become reliant on one or very few pools at small sites or to promote range expansion within large habitat areas. By 1995 proactive conservation work had been carried out at 29 (69%) of the 39 sites with extant native populations, including 8 during the recovery program. Twenty reintroductions also had been attempted, including nine during the program. At least six reintroductions resulted in the foundation of expanding new populations, and an additional eight have shown initial signs of success. Conservation methods developed for Bufo calamita should provide a useful precedent for long‐term conservation of early successional habitats and species. Programa de Recuperación para el Sapo Natterjack ( Bufo calamita ) en Gran Bretaña El sapo Natterjack (Bufo calamita) es una especie en peligro de extinción en Gran Bretaña y esta sujeto a protección desde 1975. Este anfibio sufrió una declinación importante durante la primera mitad del siglo veinte, debido en parte a la destrucción del hábitat pero principalmente a los cambios sucesionales en sus biotopos y a la acidificación antropogénica de sitios de reproducción. Además de la protección de sitios y de la especie, extensas investigaciones autoecológicas en los últimos 25 años proporcionaron las bases para un programa intensivo de recuperación patrocinado por las organizaciones de conservación de naturaleza estatutarias (English Nature y Countryside Council for Wales). Este programa se basó en el manejo del hábitat y reintroducciones en sitios restaurados, como continuación de esfuerzos similares pero menos intensivos. El manejo de brezales y dunas se enfocó en la restauración y mantenimiento de las primeras etapas sucesionales, se inició con la remoción de hierbas y vegetación leñosa invasoras y posteriormente se restablecieron regímenes de pastoreo similares a los prevalecientes en siglos anteriores. En algunos casos se proporcionaron charcas para reproducción para incrementar o estabilizar las poblaciones o para promover la expansión del rango en áreas con hábitats extensos. Para 1995 el trabajo de conservación se había desarrollado en 29 (69%) de los 39 sitios con poblaciones nativas, incluyendo 8 durante el programa de recuperación. También se habían intentado veinte reintroducciones, incluyendo 9 durante el programa. Por lo menos 6 reintroducciones resultaron en la fundación de nuevas poblaciones y 8 más han mostrado señas iniciales de éxito. Los métodos de conservación desarrollados para Bufo calamita deben constituir un precedente útil para la conservación a largo plazo de hábitats en sucesión inicial y de especies.

Past and Distant Whaling and the Rapid Decline of Sperm Whales off the Galápagos Islands - Hal Whitehead; Jenny Christal; Susan Dufault (Conservation Biology, 1997)
It is generally expected that exploited whale populations should rebuild following the end of whaling. Using photographic identification of individuals during a series of field projects, we studied female and immature sperm whales ( Physeter macrocephalus) that visit the waters off the Galápagos Islands, Ecuador. Analysis of mark‐recapture data, using a likelihood model, indicates the population decreased at a rate of about 20% per year (95% c.i. 7–32%) between 1985‐1995. During the study period the animals were not hunted and were not obviously the subject of other immediate anthropogenic threats. Rates at which research vessels encountered whales also fell over this interval. The decline seems to be due principally to migration into waters off the Central and South American mainland. The population also has a very low recruitment rate, about 0.05 calves/female/year, as indicated by rates of observation of calves. Although other causes cannot be ruled out, both the high emigration rate and low recruitment rate are probably related to heavy whaling in Peruvian waters which ended in 1981. Whales from the Galápagos are moving east to fill productive but depopulated waters near the coast, and the virtual elimination of large breeding males (in their late twenties and older) from the region has lowered pregnancy rates. The case of the Galápagos sperm whales strongly suggests that exploitation can continue to have substantial negative impacts on the size and recruitment rate of an animal population well outside the range of the hunt and for at least a decade after it has ended. Explotación en el Pasado y la Rápida Declinación de los Cachalotes de las Islas Galápagos Generalmente se espera que las poblaciones de ballenas que han sido explotadas se recuperen al término del período de explotación. Por medio de identificación fotográfica de individuos estudaimos hembras e inmaduros de cachalotes ( Physeter macrocephalus) que visitan las aguas cercanas a las Islas Galápagos, Ecuador. El análisis de datos de captura‐recaptura, utilizando un modelo de probabilidad, indica que la población declinó a una tasa aproximada de 20% por año (95% c.i. 7‐32%) entre 1985 y 1995. Durante el estudio los animales no fueron cazados ni estuvieron sujetos a otras amenazas antropogénicas inmediatas y obvias. Durante este intervalo también decrecieron las tasas de avistamiento de ballenas desde barcos de investigación. La declinación parece deberse principalmente a la migración hacia aguas cercanas a la costa de Centro y Sudamérica. La observación de crías indica que la población también tiene una tasa de reclutamiento muy baja, approximadamente 0.5 crías/hembra/año. Aunque no se pueden descartar otras causas, tanto la elevada tasa de emigración como la baja tasa de reclutamiento probablemente se deben a la cacería intensiva en aguas peruanas que terminó en 1981. Ballenas de las Galápagos se están moviendo hacia el este para ocupar aguas productivas pero despobladas cercanas a la costa y la eliminación virtual de machos reproductores (de 20 años o más) ha reducido la tasa de reproducción. El caso de los cachalotes de las Galápagos sugiere que la cacería puede causar impactos negativos significativos sobre el tamaño y la tasa de reclutamiento de una población animal fuera del área de caza y por lo menos una década después de terminada la cacería.

Handling of African Wild Dogs and Chronic Stress: Reply to East et al. - Scott Creel (Conservation Biology, 1997)

Books Received (Conservation Biology, 1997)

Pinniped Penises in Trade: A Molecular‐Genetic Investigation - S. Malik; P. J. Wilson; R. J. Smith; D. M. Lavigne; B. N. White (Conservation Biology, 1997)
This study was prompted by international concern over the expanding global trade in wildlife parts and derivatives. Pinniped (seals, sea lions, fur seals, and walrus) penises purchased in traditional Chinese medicine shops in Asia and North America were examined using molecular genetic techniques. A 261 base pair region of the cytochrome b gene was sequenced for 21 unknown samples, 3 harp seal ( Phoca groenlandica) reference samples, and 2 hooded seal ( Cystophora cristata) reference samples. These sequences were compared against published sequences for pinniped species. Eleven samples from Shanghai and 1 from Bangkok were identified as harp seals and 1 Vancouver sample was derived from a hooded seal. One sample ( from Hong Kong) was most closely associated with an Australian fur seal ( Arctocephalus pusillus doriferus), though the possibility of it originating from a Cape fur seal ( A. p. pusillus) could not be discounted due to the unavailability of a reference sequence. Seven samples were not derived from pinnipeds: 1 from Bangkok was identified as originating from domestic cattle ( Bos taurus) and the remaining 6 were not identifiable to species due to a lack of relevant published sequences. Of these 6 samples, 2 from Canada were most similar to African wild dog ( Lycaon pictus), 3 (2 from Toronto and 1 from Bangkok) were most similar to domestic cattle followed by water buffalo ( Bubalis bubalis), and 1 from San Francisco was most similar to water buffalo. Our results confirm that penises from different pinnipeds are in international trade. The detection of unidentifiable species and, possibly, the Australian fur seal—a species that is not legally hunted—suggests that legal trade in seal products is serving as a cover for illegal trade. These findings are consistent with other recent evidence that the lucrative market for pinniped penises may be encouraging the unregulated hunting of seals, including protected species, and the harvesting of other unidentified mammalian species. Venta de Penes de Pinípedos: Una Investigación Genético‐Molecular Este estudio fue impulsado por una preocupación internacional sobre la expansión global de la venta de partes de vida silvestre y sus derivados. Los penes de Pinípedos ( focas, leones marinos y morsas) vendidos en tiendas de medicina tradicional China en Asia y Norteamérica fueron examinados usando técnicas de genética molecular. Una región del gen citocromo b de 261 pares de bases fue secuenciada para 21 muestras desconocidas, 3 muestras de referencia de Phoca groenlándica y 2 de Cystophora cristata. Estas secuencias fueron comparadas contra secuencias publicadas de especies de pinípedos. Once muestras de Shangai y una de Bangkok fueron identificadas como Phoca groenlándica y una muetsra de Vancouver se derivó de Cystophora cristata. Una muestra (procedente de Hong Kong) estuvo cercanamente asociada con la foca Australiana ( Arctocephalus pusillus doriferus) aunque la posibilidad de que provenga de una foca del Cabo ( A. p. pusillus) no puede ser descartada debido a la carencia de una secuencia de referencia. Siete muestras no provenían de pinípedos: Una proveniente de Bangkok se identificó como originaria del toro doméstico ( Bos taurus) y las seis restantes no fueron identificadas debido a la carencia de secuencias relevantes publicadas. De estas 6 muestras, 2 provenientes de Canada fueron muy similares a las secuencias del perro salvaje africano ( Lycaon pictus), 3 (2 de Toronto y 1 de Bangkok) fueron muy similares al ganado domestico seguido del Búfalo del agua ( Bubalis bubalis), una muestra de San Francisco fue muy similar al Búfalo del agua. Nuestros resultados confirman que los penes de diferentes pinípedos son vendidos en el mercado internacional. La detección de especies no identificables y posiblemente la presencia de la foca Australiana—una especie cazada ilegalmente—sugiere que la venta legal de poductos de focas esta sirviendo como cobertura para la venta ilegal. Estos resultados son consistentes con otras evidencias recientes que muestran que el lucrativo mercado de penes de pinípedos podría estar formentando la caza no regulada de focas, incluyendo a especies protegidas, además de la captura de otras especies de mamíferos no identificados. X82292 X72209 X82294 L39209 U12851 X82297 X82293 U12831 X82302 X82304 X82298 X72005 X82301 D34635

A Forager‐Resource Population Ecology Model and Implications for Indigenous Conservation - Bruce Winterhalder; Flora Lu (Conservation Biology, 1997)
Population ecology and foraging theory can be combined to simulate the population dynamics of hunter‐gatherers and their prey resources. Such simulation study is important to issues of conservation because many of the population processes that link human foragers and their prey occur over time scales that elude both ethnographic and archaeological fieldwork. To demonstrate, we used the model to examine hunter‐gatherer population dynamics. We focused on a prey characteristic that affects its susceptibility to over‐exploitation: the intrinsic rate of increase, r. We found that forager‐prey systems can stabilize without intentional conservation behavior and that prey “switching,” fall‐back foods, and in certain circumstances, a higher r contribute to resource species persistence. Furthermore, a prey’s vulnerability to local depletion or extinction may depend on the demographic characteristics of the suite of resources harvested along with it. The model can serve as a “null hypothesis” for examining intentional resource conservation and presents points in concordance with, as well as divergent from, tenets in conservation biology. In particular, we discuss the implications of these findings for indigenous resource conservation in Amazonia (e.g., the overhunting of large primates and avifauna and the adoption of new procurement technologies) as well as the “Pleistocene Overkill Hypothesis.” Modelo de Ecología Poblacional Forraje‐Recurso y sus Implicaciones en la Conservación Local La ecología de poblaciones y la teoría de forraje se puede combinar para investigar la dinámica poblacional entre cazadores‐recolectores y sus especies de presa. Este tipo de investigación basada en el uso de simulaciones por computadora es importante para el tema de la conservación del medio, puesto que muchos de los procesos poblacionales entre cazadores‐recolectores y sus presas ocurren a una escala temporal que elude tanto a la etnografía como a la arqueología. Como desmostración, usamos este modelo para examinar la dinámica poblacional de cazadores‐recolectores. Nos concentramos en una característica de las presas que afecta su susceptibilidad de sobre‐explotación: el ritmo intrínseco de crecimiento, r. Comprobamos que el sistema de cazador‐recolector puede estabilizarse sin una conducta deliberada de conservación y que cambios de presa, comida de emergencia y algunas veces, un valor de r mayor, contribuyen a la persistencia de especies. La vulnerabilidad de una presa al decremento local o extinción puede depender de las características demográficas de las especies que están siendo recolectadas junto con la presa. Este modelo se puede usar como una “hipótesis nula” para una investigación sobre la conservación intensional de recursos y presenta puntos tanto en concordancia como de divergencia con principios de la biología de la conservación. En particular discutimos las consecuencias de este modelo para la conservación de recursos locales en la Amazonía (i.e., la sobre‐explotación de primates grandes y avifauna y la adopción de nuevas tecnologías) así como la “Hipótesis de la Mortandad Masiva del Pleistoceno.”

Impact of Hunting on Large Vertebrates in the Mbaracayu Reserve, Paraguay - Kim Hill; Jonathan Padwe; Carlos Bejyvagi; Ambrosio Bepurangi; Felipe Jakugi; Roberto Tykuarangi; Tito Tykuarangi (Conservation Biology, 1997)
Over 1,400,000 m of line transect data were collected in collaboration with Ache Indians to determine encounter rates with all large vertebrates in the Mbaracayu Reserve Paraguay. The data were analyzed using logistic regression in order to determine the impact of human hunting on animal encounter rates in the reserve. The method controlled for effects of season, weather, time of day, and habitat in order to statistically isolate the human predation effect. Encounters with the animals themselves as well as fresh signs of their activity allowed us to determine whether lower encounter rates in hunted zones are simply due to increased wariness by target species. Our results show that areas near hunters are hunted more frequently, and that Dasypus novemcinctus, Cebus apella, Tapirus terrestris, and Mazama spp. are all encountered at lower rates in those areas than in unhunted zones. We were unable to show that encounter rates with other important game species have been affected by human hunting. Demonstration of local depletion by central place foragers is expected, however, and cannot be used to conclude that prey species are in danger of regional extirpation. Impacto de la Captura de Vertebrados Mayores en la Reserva de Mbaracayu, Paraguay Datos de mas de 1,400,000 m de transectos en linea fueron colectados en colaboración con los indios Ache para determinar las tasas de encuentro con vertebrados mayores en la reserva Mbaracayu del Paraguay. Los datos fueron analizados usando regresión logística para determinar el impacto de la cazería sobre la tasa de encuentros en la reserva. El método fue controlado para aislar el efecto de la depredación humana de los efectos de la estación, el clima, la hora del día y el tipo de habitat. Los encuentros con animales, así como marcas frescas de su actividad nos permitieron determinar si las tasas bajas de encuentros en las zonas de caza son simplemente debidas al incremento en la alerta de las especies blanco. Nuestros resultados muestran que las áreas cercanas a los cazadores son utilizadas mas frecuentemente y que Dasypus novemcinctus, Cebus apella, tapirus terrestris y Mazama spp. se encuentran todos en menor proporción que en las áreas no utilizadas para la cazería. No pudimos demostrar que las tasas de encuentros con otras especies de caza importantes han sido afectadas por la caza humana. Esperamos una disminución local debida a la presencia de forrajeros centrales, aunque esto no puede ser utilizado para concluir que las especies de presas se encuentran en peligro de una extirpación regional.

Inferring the Geographic Origins of “Refugee” Chimpanzees in Uganda from Mitochondrial DNA Sequences - Tony L. Goldberg (Conservation Biology, 1997)

Nonequilibrium Dynamics between Catastrophic Disturbances and Old‐Growth Forests in Ponderosa Pine Landscapes of the Black Hills - Douglas J. Shinneman; William L. Baker (Conservation Biology, 1997)
An emerging goal of ecosystem management is to maintain ecosystems within their range of natural variability, which requires attention to pre‐EuroAmerican landscape‐scale processes and corresponding landscape structures (e.g., old‐growth forest distribution). The prevailing “equilibrium” view of ponderosa pine forest landscapes, for example, holds that frequent, low‐intensity surface fires maintained open, park‐like forests of large, old trees. Yet a contrasting “nonequilibrium” view suggests that some forest ecosystems are subject to unpredictable catastrophic disturbances that dramatically alter these ecosystems. To assess these views’ relevance, we examined early historical accounts and records of natural disturbances in the ponderosa pine forests of the Black Hills in South Dakota and Wyoming ( U.S.A.). There is evidence of frequent, low‐intensity surface fires and large, catastrophic disturbances before EuroAmerican influence. Several large, stand‐replacing fires occurred between 1730 and 1852, and, shortly after EuroAmerican settlement, a major outbreak of mountain pine beetles ( Dendroctonus ponderosae Hopk.) occurred. The location of these severe disturbances coincides geographically with early explorers’ reports of extensive tracts of relatively dense closed‐canopy forests, including some very large patches (5000+ ha) of dense old growth. This contrasts with sparse, open‐canopy forests thought to be maintained by periodic, low‐intensity surface fires. We suggest that the cooler, moister, central and northern Black Hills and topographically protected areas may have been dominated by infrequent, catastrophic disturbances that maintained large patches of dense forests, including large, contiguous patches of old growth, in a relative state of nonequilibrium. The warmer and drier southern Black Hills, south‐facing slopes, and exposed areas may have been dominated by frequent, low‐intensity surface fires and other small disturbances that maintained open‐canopy forests in a relative state of equilibrium. Proposed Black Hills National Forest management plans that exclusively endorse the equilibrium view are misdirected and will move the forest ecosystem farther outside its range of natural variability. Desequilibrio Dinámico entre Perturbaciones Catastróficas y Bosques Maduros en Paisajes de Pino Ponderosa de Black Hills Una meta del manejo de ecosistemas es mantenerlos dentro de su rango de variabilidad natural, lo cual requiere de considerar procesos pre‐euroamericanos a escala de paisaje y las correspondientes estructuras del paisaje (e.g., distribución de bosques maduros). Por ejemplo, la visión prevaleciente del “equilibrio” de paisajes de bosque de pino ponderosa sostiene que frecuentes fuegos superficiales de baja intensidad mantenían bosques “similares a parques” abiertos con árboles grandes y viejos. Pero, una contrastante visión de “desequilibrio” sugiere que algunos ecosistemas de bosque están sujetos a perturbaciones catastróficas impredecibles que los altera dramáticamente. Para evaluar la pertinencia de estas visiones examinamos informes históricos tempranos y registros de perturbaciones naturales en los bosques de pino ponderosa de Black Hills en Dakota del Sur y Wyoming (E.U.A.). Hay evidencia de frecuentes fuegos superficiales de baja intensidad y grandes perturbaciones catastróficas anteriores a la influencia euroamericana. Entre 1730 y 1852 ocurrieron varios incendios mayores y, poco después de la colonización euroamericana, el escarabajo de pino de montaña ( Dendroctonus ponderosae Hopk.) causó grandes daños. La localización de estas perturbaciones severas coincide geográficamente con los reportes de exploradores respecto a extensas zonas de bosques de dosel cerrado relativamente densos, incluyendo unas extensiones muy grandes (5000+ha) de bosque maduro denso. Esto contrasta con los bosques de dosel abierto dispersos que se pensaba eran mantenidos por los incendios de baja intensidad periódicos. Sugerimos que, por su mayor frescura y humedad, las Black Hills centrales y del norte y las áreas topográficamente protegidas pudieron haber sido dominadas por perturbaciones catastróficas infrecuentes que mantenían grandes extensiones de bosques densos, incluyendo grandes parches contiguos de bosque maduro, en un relativo estado de desequilibrio. Las Black Hills del sur y las laderas del sur, más cálidas y secas, pudieron haber sido dominadas por incendios de baja intensidad frecuentes y otras perturbaciones pequeñas que mantenían bosques de dosel abierto en un relativo estado de equilibrio. Los planes de manejo propuestos para el Bosque Nacional Black Hills que exclusivamente avalan la visión de equilibrio están mal orientados y llevarán al ecosistema del bosque más allá de su rango de variabilidad natural.

Comparing the Effects of Landscape Fragmentation by Forestry and Agriculture on Predation of Artificial Nests - Erin M. Bayne; Keith A. Hobson (Conservation Biology, 1997)
Fragmentation of forested landscapes can reduce the reproductive success of birds occupying residual forest patches. Previous studies, however, have focused primarily on how nest predation can change when landscapes become fragmented by agriculture rather than by logging. To determine if predation on artificial nests in forest patches was influenced by the surrounding landscape, we placed ground and shrub nests along the edge and interior of forest patches located in agricultural, logged, and contiguous forest landscapes within a single region of the southern boreal mixedwood forest of central Canada. Nest predators were identified using remotely triggered cameras and by marks left in plasticine eggs, whereas the relative abundance of nest predators such as corvids and small mammals was estimated by surveys and live‐trapping. The percentage of ground nests destroyed at the edge and interior of patches in the logged and contiguous forest landscapes was significantly lower than at the edge or interior of patches in the agricultural landscape. No differences in predation rate were observed for shrub nests among landscapes. We attributed higher rates of predation in the agricultural landscape to higher densities of red squirrels ( Tamiasciurus hudsonicus) in the interior and a greater diversity of predators along edges. The similarity in predation rate between logged and contiguous forest landscapes suggests that fragmentation caused by logging may result in little change in predator communities and in this respect, might be similar to fragmentation caused by natural disturbance regimes such as fire. In contrast, fragmentation by agriculture seems to have more serious consequences for nesting birds. Policy changes that limit the growth of agriculture in the southern boreal mixedwood forest are required to conserve the diverse avifauna of this region. Comparación de los Efectos de la Fragmentación del Paisaje Causada por la Acción Forestal y Agrico sobre la Depredación de Nidos Artificiales La fragmentación de paisajes forestales puede reducir el éxito reproductivo de aves que ocupan los parches residuales del bosque. Sin embargo, estudios previos se han enfocado principalmente al modo en que puede cambiar la depredación de nidos cuando los paisajes son fragmentados para agricultura en lugar de para forestería. Para determinar si el paisaje circundante influyel sobre la depredación de nidos artificiales, en parches de bosque colocamos nidos sobre el suelo y en arbustos a lo largo del borde y en el interior de parches de bosque, localizados en paisajes agrícolas, talados, de bosque continuo, en una sola región del bosque boreal mixto de Canadá central. Los depredadores de nidos fueron identificados mediante cámaras disparadas remotamente y por marcas dejades en huevos de plastilina, mientras que la abundancia relativa de depredadores de nidos como corvídos y mamíferos pequeños se estimó mediante reconocimientos y trampeos. El porcentaje de nidos sobre el suelo destruidos en el borde e interior de parches en los paisajes talados y continuos fue significativamente menor que en el borde o interior de parches en el paisaje agrícola. No se observó diferencia en las tasas de depredación de nidos en arbustos en los paisajes estudiados. Atribuimos las mayores tasas de depredación en el paisaje agrícola a la mayor densidad de ardillas rojas ( Tamiascuirus hudsonicus) en el interior y a una mayor diversidad de depredadores en los bordes. La similitud de tasas de depredación en paisajes talados y continuos sugiere que la fragmentación causada por la forestería puede producir cambios pequeños en las comunidades de depredadores y en este sentido puede ser similar a la fragmentación causada por regímenes de perturbación natural tales como fuego. En contraste, la fragmentación por agricultura parece tener consecuencias más serias para aves anidantes. Se requieren cambios políticos para limitar la expansión de la agricultura en el bosque boreal mixto para conservar la diversidad de la avifauna de esta región.

A Plea from the Last of the Maya‐Itzá - Reginaldo Chayax Thinsp; David F. Whitacre Thinsp (Conservation Biology, 1997)

Tests of Null Models for Amphibian Declines on a Tropical Mountain - J. Alan Pounds; Michael P. L. Fogden; Jay M. Savage; George C. Gorman (Conservation Biology, 1997)
Many of the recent, widespread declines and disappearances of amphibian populations have taken place in seemingly undisturbed, montane habitats. The question of whether the observed patterns differ from those expected from natural population dynamics is the subject of an ongoing controversy with important implications for conservation. We examined this issue for the Monteverde region of Costa Rica’s Cordillera de Tilarán, where a multi‐species population crash in 1987 led to the disappearance of the endemic golden toad ( Bufo periglenes) and many other species. Focusing on long‐term studies of other amphibian assemblages, we developed probabilistic null models for the number of disappearances. Tests of these models at Monteverde suggest that the patterns observed there are highly improbable in the context of normal demographic variability. Twenty species of frogs and toads (40% of the anuran fauna) were missing throughout our 1990–1994 surveys of a 30‐km 2 area. Not all organisms in this area had declined accordingly: the relative frequency of absences was much greater for anurans than for breeding birds. Nevertheless, anuran habitats, most of which are protected within the Monteverde Cloud Forest Preserve, seemed unchanged, and none of the breeding‐bird species known to be sensitive to deforestation was missing. Thus, only factors other than direct, obvious human impacts can explain the amphibian declines. Consistent with our tests of null models, analyses of recent population trends do not support the hypothesis that the 1987 crash was an extreme fluctuation from which populations are recovering. Surviving species for which baseline data are available—stream‐breeding glass frogs ( Hyalinobatrachium fleischmanni and Centrolenella prosoblepon) and a pond‐breeding treefrog ( Hyla pseudopuma)—remained far less abundant than they were before the crash and showed no increase during 1990‐1994. We documented an increase only for one terrestrial‐breeding rain frog ( Eleutherodactylus diastema). Pruebas de Modelos Nulos para Disminuciones de Anfibios en una Montaña Tropical Muchas de las disminuciones y desapariciones recientes de poblaciones de anfibios en varias partes del mundo se han producido en hábitats que aparentemente no han sido alterados. La pregunta de si los patrones observados difieren de lo que es predicho por la dinámica natural de poblaciones es el tema de una controversia actual que tiene consecuencias importantes para la conservación. Se examinó esta pregunta para la región de Monteverde en la Cordillera de Tilarán, Costa Rica, donde un colapso de poblaciones en 1987 produjo la desaparición del endémico sapo dorado ( Bufo periglenes) y muchas otras especies. Centrándose en estudios a largo plazo sobre anfibios de otras regiones, se desarrollaron modelos nulos probabilísticos con respecto al número de desapariciones. Al probarse estos modelos para Monteverde se sugiere que los patrones observados son poco probables dentro de los parámetros normales de la variabilidad demográfica. Durante 1990‐1994 en un área de 30‐km 2 , veinte especies de ranas y sapos (el 40% de los anuros de la región) estuvieron ausentes. No todos los organismos del área disminuyeron de la misma forma: por ejemplo, la frecuencia relativa de especies ausentes fue mucho mayor para los anuros que para las aves que se reproducen en el área de estudio. Sin embargo, la mayoría de los hábitats de anuros están protegidos dentro de la Reserva Biológica Bosque Nuboso de Monteverde, y no parecía que habían cambiado. Además, ninguna de las especies de aves que son afectadas de manera negativa por la deforestación estuvo ausente. Por lo tanto, las disminuciones de anfibios sólo pueden ser explicadas por factores que no son los impactos obvios y directos causados por los seres humanos. De acuerdo con nuestras pruebas de modelos nulos, los análisis de tendencias recientes de abundancia no apoyan la hipótesis de que el colapso de 1987 fuera una fluctuación extrema de la cual las poblaciones están recuperándose. Las especies sobrevivientes de las que existen datos demográficos anteriores al colapso—ranas de vidrio ( Hyalinobatrachium fleischmanni y Centrolenella prosoblepon), que se reproducen en quebradas, y una rana arborícola ( Hyla pseudopuma) que pone huevos en lagunas y pozos—eran mucho menos abundantes durante 1990–1994 de lo que fueron antes de este evento y no se encontró evidencias de aumento. Se documentó un incremento solo en las poblaciones de Eleutherodactylus diastema, que se reproduce en hábitats terrestres.

Effects of Anthracnose on Dogwood Mortality and Forest Composition of the Cumberland Plateau (U.S.A.) - John Kevin Hiers Thinsp; Jonathan P. Evans (Conservation Biology, 1997)
Throughout the eastern deciduous forest, flowering dogwood (Cornus florida) continues to decline due to the introduction of the fungus Discula destructiva, the cause of dogwood anthracnose. We compared the responses of dogwood populations to the anthracnose in both the mixed mesophytic forest of the Cumberland Plateau coves and the oak‐hickory forest of the plateau uplands. We surveyed dogwood populations in four randomly located 0.1‐ha plots in each forest site, and we surveyed community composition in eight randomly located 0.05‐ha plots in each study forest. This study is the first to document dogwood mortality due to anthrac‐nose within the geophysiological province of the Cumberland Plateau. Factors affecting the rate of anthrac‐nose spread (evaporative potential, soil moisture, and light levels) differed between the coves and uplands, but trends in the data suggest that dogwood may be eliminated from each of the forests we studied. Moreover, changes in plant community composition since introduction of the fungus show an increase in two bird‐dispersed species—blackgum ( Nyssa sylvatica ) and spicebush ( Lindera benzoin )—concurrent with declining dogwood populations. Decomposition of dogwood litter plays an important role in calcium cycling in these forests, and, on the poorly buffered soils of the Cumberland Plateau, calcium retention could lead to a decline in passerine birds, that depend on calcium for their shells, through loss of invertebrate food sources. As the dogwood anthracnose epidemic continues and the largest size classes of dogwood disappear, additional changes in species composition and community dynamics are likely to occur in these forests. Efectos de Antracnosa en la Mortalidad de Cornus florida y la Composición del Bosque de la Meseta Cumberland (USA) Cornus florida continúa deteriorándose en los bosques deciduos del este de los Estados Unidos a causa de la introducción de un hongo destructivo: Discula destructiva. Este estudio compara las respuestas de las poblaciones de Cornus florida al hongo en los bosques mesófilos mezclados de los cañones de la Meseta y en los bosques de encino hickory en las tierras altas de la meseta. Este estudio representa la primera documentación del deterioro de Cornus florida dentro de la provincia geofisiológica de la Meseta de Cumberland. Además, utilizando una serie de datos del bosque mesófilo mezclado, este estudio ilustra los cambios en la composición del bosque desde la introducción del hongo. Los factores que afectan la tasa de crecimiento del hongo (potencial evaporativo, humedad del suelo y nivel de luz) son distintos entre los cañones y las tierras altas, sin embargo, la tendencia en los datos sugiere que Cornus florida podría ser eliminado de los bosques estudiados. Un análisis de cambios en la composición de la comunidad desde la introducción del hongo demuestra un aumento de dos especies diseminados por aves ( Nyssa sylvatica y Lindera benzoin ), al mismo tiempo que decrecen las poblaciones de Cornus florida. Se anticipan cambios en el reciclaje de nutrientes relacionados a pérdidas de Cornus florida en la Meseta.

Factors Affecting the Density and Distribution of Wild Dogs in the Kruger National Park - Michael G. L. Mills; Martyn L. Gorman (Conservation Biology, 1997)
African wild dogs ( Lycaon pictus) are a seriously endangered species with only around 5000 individuals left. We examined the factors likely to be affecting the distribution and density of wild dogs living in the Kruger National Park, South Africa. We collected data, by traditional and satellite radio‐tracking, on diet selection, sizes of packs, dispersion and sizes of territories, and patterns of habitat selection for eight packs of wild dogs. In Kruger wild dogs specialize on impala ( Aepyceros melampus) and kudu ( Tragelaphus strepsiceros). They live in packs averaging about nine dogs and inhabit territories of 350–950 km 2 . Neighboring territories overlap to some extent but packs meet very rarely. The dispersion pattern of food plays only a minor role in determining the density and distribution of dogs in the Kruger; dogs exist at their lowest density where their food is most abundant. This apparent paradox comes about because the dogs seem to avoid areas that, although prey‐rich, are heavily used by lions. This is a sensible strategy because lions are a major cause of dog mortality, accounting for some 39% of natural pup deaths and at least 43% of natural adult deaths. Wild dogs may be conserved most successfully in areas with moderate to low densities of lions and spotted hyenas, and management strategies should be careful not to promote these species to the detriment of wild dogs and other carnivores. The densities of lions and spotted hyenas should be important criteria when considering an area for the reintroduction of wild dogs and other similar sized carnivores. Factores que Afectan la Densidad y Distribución de Perros Salvajes en el Parque Nacional Kruger El perro salvaje africano ( Lycaon pictus) es una especie en serio peligro de extinción, con una población estimada de solamente 5000 individuos. Hemos examinado los factores que con mayor probabilidad afectan la distribución y densidad de los perros salvajes que habitan el Parque Nacional Kruger en Sudáfrica. Información sobre la selección de alimento, tamaño de grupo, dispersión y tamaño de territorio y patrones de selección de hábitat fué colectada usando métodos tradicionales y seguimiento con satélite para ocho grupos de perros salvajes en el parque. Esta especie se especializa en impala ( Aepyceros melampus) y kudu ( Tragelaphus strepsiceros). Vive en grupos de 9 individuos en promedio y habita un territorio de 350‐950 km 2 . Territorios vecinos se sobreponen en cierta proporción, pero los encuentros entre diferentes grupos raras veces ocurren. El patrón de dispersión de la comida juega solo un pequeño papel en la determinación de la densidad en lugares donde la comida es mas abundante. Esta aparente paradoja es consecuencia de que los perros parecen evitar zonas que, a pesar de ser ricas en presas, también son muy usadas por leones (Panthera leo). Esta estrategia es sensata, pues esta especie es una de las mayores causas de mortalidad para los perros, alcanzando un 39% de mortalidad natural de los cachorros y al menos un 43% de la mortalidad natural de los adultos. Los perros salvajes podrían ser conservados con mas éxito en zonas con una densidad moderada o baja de leones y hienas manchadas (Crocuta crocuta). Las estrategias de conservación deben ser cuidadosamente estudiadas para evitar favorecer estas especies en detrimento de los perros salvajes y otras especies de carnívoros. La denisdad de leones y hienas manchadas deberá ser un criterio importante cuando se considere una zona para la reintroducción de los perros salvajes y otros carnívoros de similar tamaño.

Oligonucleotide probe technology as applied to the study of harmful algal blooms - John V. Tyrrell; Patricia R. Bergquist; David J. Saul; Lincoln MacKenzie; Peter L. Bergquist (New Zealand Journal of Marine and Freshwater Research, 1997)
Harmful algal bloom (HAB) research and monitoring has traditionally been based on ecological and microbiological measurements which are laborious, time‐consuming, and reliant on experienced operators. Recent developments in oligonucleotide probe technology and immunofluorescence research have revealed several potential applications and techniques that may be transposable to laboratory and field‐based monitoring and research. Field trials are currently underway for fluorescent in situ hybridisation and sandwich hybridisation assays. The former is particularly suited for laboratory‐based research on harmful algal bloom (HAB) population dynamics and structure, whereas the sandwich hybridisation assays based on a portable robotics workstation, offers the potential of quick and reliable laboratory and possibly field‐based screening for HAB species. Initial development is underway for molecular beacons and the Qß replicase detection system, both offer the potential of simple and cost effective strategies for field‐based monitoring by people with minimal knowledge of molecular biology.

Land use, associated eel production, and abundance of fish and crayfish in streams in Waikato, New Zealand - Brendan J. Hicks; Helen M. C. McCaughan (New Zealand Journal of Marine and Freshwater Research, 1997)
The density and biomass of fish and crayfish, and the production of eels, was compared among streams in native forest, exotic forest, and pasture. Populations were estimated by multiple‐pass electroshocking at 11 sites in hill‐country streams in the Waikato region, North Island. Three sites were in native forest, four in exotic forest, and four in pasture. Length of stream sampled at each site was 46–94 m (41–246 m 2 in area), and catchment areas up stream of the sites ranged from 0.44 to 2.01 km 2 . A total of 487 fish were caught. The species were longfinned and shortfinned eels, banded kokopu, Cran's and redfinned bullies, and common smelt. Eels were the most abundant fish in all three land‐use types, and shortfinned eels were more abundant at pastoral sites (mean density 1.11 fish m −2 ) than longfinned eels (mean density 0.129 fish m −2 ). Banded kokopu were present only at forested sites. Mean fish densities were greater at pastoral sites (1.55 fish m −2 ) than under either native forest (0.130 fish m −2 ) or exotic forest (0.229 fish m −2 ). Mean fish biomass was also greater at pastoral sites (89.7 g m −2 ) than under native forest (12.8 g m −2 ) or exotic forest (19.3 g m −2 ). Longfinned eels made a greater contribution to the fish biomass at all sites than did shortfinned eels. Densities of crayfish were high (0.46–5.40 crayfish m −2 ), but were not significantly different between land‐use types. Crayfish biomass ranged from 1.79 to 11.2 g m −2 . Total eel production was greater at pastoral sites (mean 17.9 g m −2 year 1 ) than at forest sites (mean 2.39 gm −2 year −1 ).

Successive macrophyte invasions within the submerged flora of Lake Tarawera, Central North Island, New Zealand - Rohan D. S. Wells; Mary D. de Winton; John S. Clayton (New Zealand Journal of Marine and Freshwater Research, 1997)
Lake Tarawera is the lake with the clearest water in New Zealand to be invaded by four particularly successful invasive adventive weeds: Ceratophyllum demersum, Egeria densa, Elodea canadensis , and Lagarosiphon major. E. canadensis was the first to invade the lake followed by L. major which became the dominant tall‐growing species to 6 m depth. Comparisons of lake survey data for macrophytes in Lake Tarawera from 1988 and 1993/94 show that marked changes occurred in the composition and patterns of submerged vegetation as a result of a recent invasion by C. demersum . This species was first recorded in 1988 as infrequent, within a restricted area of the lake. Within 5 years it occurred in 52% of the lake profiles, had a depth range of 0.5–15.5 m, and a median average cover estimated to be between 51 and 75% throughout this depth range. The spread of C. demersum has been at the expense of native vegetation (particularly Characean meadows) and E. canadensis. E. densa was first recorded at the same time as C. demersum but has established slowly at localised sites only ( E. densa dominating to 10 m depth and C. demersum as a monospecific stand from 10 to 14.5 m. Their abundance in Lake Tarawera suggests that clear‐water New Zealand lakes and their native vegetation could be severely impacted if these presently restricted species become more widely distributed.

Responses to pH of nine fishes and one shrimp native to New Zealand freshwaters - David W. West; Jacques A. T. Boubée; Rhys F. G. Barrier (New Zealand Journal of Marine and Freshwater Research, 1997)
The pH values preferred and avoided by adult stages of inanga (Galaxias maculatus) , common bully ( Gobiomorphus cotidianus) , common smelt (Retropinna retropinna) , and redfinned bully (G. huttoni) , were determined in a gradient tank (pH ranges of 3.2–11.2). Juvenile stages of inanga, common bully, shortjawed kokopu ( Galaxias postvectus) , koaro (G. brevipinnis) , banded kokopu ( G. fasciatus) , shortfinned (Anguilla australis) and longfinned ( A. dieffenbachii) elvers and glass eels, as well as freshwater shrimp (Paratya curvirostris) were also tested. Most species were found to have pH preferences and all except inanga avoided pH values of above c. 9.5. Adult fish showed stronger preferences than juveniles. An avoidance of pH values below 6.5 was apparent in most species except shortfinned elvers, koaro, and banded kokopu. Results indicate that the range of pH encountered in lowland streams are unlikely to have a major impact on the distribution of most New Zealand native freshwater fish.

Seasonal and spatial dynamics in the phytomacrofaunal community of Lake Henley, New Zealand - R. J. Miller; R. G. Death (New Zealand Journal of Marine and Freshwater Research, 1997)
The invertebrate communities associated with dense beds of exotic macrophytes were sampled monthly between June 1993 and June 1994 from three sites in Lake Henley, a small artificial lake in the Southern Wairarapa, North Island, New Zealand and from a small stream flowing into the lake. All communities were dominated by either the gastropod Potamopyrgus antipodarum or by oligochaetes. Community composition was similar at sites within the lake monoculture but changed seasonally. These changes appeared to be predominantly a result of seasonal fluctuations in the presence of filamentous algae on the macrophyte beds. Communities sampled from the stream site had a number of taxa in common with the lake communities but were quite distinctive in terms of the relative abundance of these component taxa. The diversity of the lake phytomacrofauna community, although comparable to similar studies in other New Zealand lakes, had a lower proportion of insect taxa perhaps because of the low floral diversity, the lack of depth variation, the absence of a nearby colonising source or the young age of the lake.

Effects of crayfish ( Paranephrops planifrons : Parastacidae) on in‐stream processes and benthic faunas: A density manipulation experiment - Stephanie M. Parkyn; Charles F. Rabeni; Kevin J. Collier (New Zealand Journal of Marine and Freshwater Research, 1997)
The effects of New Zealand freshwater crayfish or koura ( Paranephrops planifrons: Parastacidae) on organic matter processing, sediment accumulation, and benthic invertebrate communities were investigated using four replicate treatments of 0 (control), 4–5 (medium), and 8–11 (high) similar‐sized koura in 0.5 m 2 artificial stream channels colonised by benthic invertebrates from a pasture stream, Waikato, New Zealand. Wineberry ( Aristotelia serrata ) leaf packs were placed in each channel and after 7 weeks the leaf matter remaining was significantly lower in both medium and high koura channels than in controls. The amount of sediment (surficial cover by fines and weight of suspendable sediment) was also significantly reduced in high koura density channels. Densities of invertebrates other than crayfish were not significantly different among treatments; however, taxa richness and invertebrate biomass were significantly lower in high koura channels than in controls. Our results suggest that freshwater koura may play a keystone role in structuring benthic invertebrate communities either directly through predation, or indirectly by sediment bioturbation and increasing organic matter processing rates.

Sea level and sea surface temperature variability at the Chatham Islands, New Zealand - Basil R. Stanton (New Zealand Journal of Marine and Freshwater Research, 1997)
Sea level and sea surface temperature variability at the Chatham Islands was investigated using data from 1992 to 1994. The study was aimed at testing the hypothesis that the Subtropical Convergence moves north and south of the islands and that the resulting (in phase) variations in sea level and satellite Sea Surface Temperature could be observed and hence used to reveal something about the temporal scales of these movements. Although variability at a variety of scales was observed there was little evidence for verification of the hypothesis. Sea level adjustment to changes in atmospheric pressure was found to be less than the conventional inverted barometer response, showing that local and/or remote wind forcing was contributing to the observed sea level variability. However no simple local remote forcing mechanism could be identified in the data. In contrast sea surface temperature anomalies were correlated with local meridional winds stress.

On stream periphyton‐turbulence interactions - V. I. Nikora; D. G. Goring; B. J. F. Biggs (New Zealand Journal of Marine and Freshwater Research, 1997)
A set of experiments was carried out to determine what effects periphyton communities could have on near‐bed hydraulic fields. We analysed velocity distribution, skewness and kurtosis coefficients, Reynolds stresses, relative turbulence intensity, coefficient of eddy diffusivity, velocity spectra, and turbulence scales at two flows with, and without, diatom‐dominated periphyton on the bed. We found that turbulence was affected by the periphyton mat selectively. The largest influence occurred for the velocity distribution, Reynolds stress, coefficient of eddy diffusivity, and velocity cross‐spectra. Changes as a result of the periphyton mat were revealed in the large‐scale turbulence structure. The periphyton affected not only the region near the bottom but also the entire logarithmic layer. The periphyton mat increased roughness length by a factor of ≈5 whereas the integral resistance to flow (reciprocal Chezy coefficient and Manning's roughness coefficient) was increased by 20–25%. The microscale turbulence structure was investigated using values of Kolmogorov's microscale η K . These appeared to be commensurate with the characteristic scales of periphyton filaments. This allowed us to hypothesise that the mechanism of the “periphyton‐turbulence” interaction is connected, to a certain degree, with viscous effects.

Summer light‐trap catches of adult Trichoptera in hill‐country catchments of contrasting land use, Waikato, New Zealand - Kevin J. Collier; Brian J. Smith; Brenda R. Baillie (New Zealand Journal of Marine and Freshwater Research, 1997)
The distribution of adult Trichoptera in light traps was investigated alongside nine streams draining catchments under native forest, pine forest, or pasture near Hamilton, Waikato, New Zealand. The aim of the study was to determine the relationship between abundance, taxonomic richness, and community composition with respect to land use during summer, and to evaluate the use of adult Trichoptera compared with benthic invertebrates as potential bio‐indicators of the effectiveness of land‐management changes. Adult Trichoptera faunas alongside the native streams were dominated by Hydrobiosidae, Conoesucidae, and Helicopsychidae (each >10% of total Trichoptera numbers for at least two of the three sites), whereas Leptoceridae, Oeconescidae, and Hydrobiosidae were relatively abundant alongside at least two of the pine sites. Adult Trichoptera faunas at the pasture sites were strongly dominated by Hydroptilidae which made up 47–85% of numbers caught at all sites. The mean number of individuals and taxa caught in light traps increased from November to January and then declined in February for all land‐use types. Overall, total numbers and taxonomic richness of adult Trichoptera were significantly lower at the pine sites compared to the pasture or native sites. TWINSPAN classification of benthic invertebrates collected in November clearly differentiated sites based on land use for presence/absence and percentage abundance data. A similar pattern was evident for most sites when adult Trichoptera faunas were used for the four sampling dates combined, suggesting that light trapping has potential as a tool for bio‐monitoring.

Land‐water interactions at Whatawhata, New Zealand: Introduction and synthesis - John M. Quinn; A. Bryce Cooper (New Zealand Journal of Marine and Freshwater Research, 1997)
A programme of research is introduced on the effects on stream ecosystems of land‐use change from native forest to pasture, and subsequent re‐afforestation with exotic pine plantations. The results detailed in the 11 accompanying papers conclude that land‐use change has had strong effects on many key physical, chemical, and biological aspects of stream ecosystems in and adjacent to Whatawhata Research Centre, near Hamilton, New Zealand. Six of these papers compare streams, draining catchments with similar topography, geology, and soils, to investigate land‐use effects on stream lighting, water quality, channel morphology, benthic and hyporheic habitat and faunas, fish, and food webs. Two papers investigate hypotheses on the influence of shade and crayfish using streamside mesocosms. Finally, three papers use the experimental sites to evaluate methods for studying crayfish populations, stream carbon pathways, and a stream temperature model. These studies provide a comprehensive description of land‐use effects on physical, chemical, and biological characteristics of streams and contribute to the basis for future long‐term ecological research on the effects on streams of sustainable land management practices.

The East Auckland Current, 1994–95 - Basil R. Stanton; Philip J. H. Sutton; Stephen M. Chiswell (New Zealand Journal of Marine and Freshwater Research, 1997)
The East Auckland Current (EAUC) was investigated in 1994–95 using data from three CTD surveys (conductivity, temperature, depth) and moored current meters. The strength and position of the EAUC was found to be highly variable with most of the current re‐circulating around an anticyclonic eddy north‐east of North Cape—the North Cape Eddy. The position and intensity of this eddy changed resulting in complex flow patterns with a south‐east flowing EAUC not always present as a contiguous feature. The current meter data showed a high level of mesoscale variability with low spatial coherence, suggesting that the along shore correlation length scale was c. 100 km in this current system. Near North Cape, a persistent but variable counter‐current was found inshore of the EAUC. To the south‐east a permanent anticyclonic East Cape Eddy found north of East Cape appears to dominate the flow field and the genesis of the East Cape Current.

Stream channels are narrower in pasture than in forest - Robert J. Davies‐Colley (New Zealand Journal of Marine and Freshwater Research, 1997)
In the Hakarimata Range, west of Hamilton, New Zealand, second‐order streams appear to be wider in native than in pasture catchments, whereas streams in pine plantations (18 years old) appear to be suffering active stream‐bank erosion. A working hypothesis to explain these observations was that pasture vegetation replacing original forest encroaches on the stream channel, causing it to become narrower. To test the hypothesis, channel widths were measured up stream and down stream of “transitions” from native forest to pasture in 20 streams of different size in marginal ranges of the Waikato Basin. Small streams (catchment area 2 , width in forest 30 km 2 , width in forest >10 m). This narrowing of stream channels implies that native forest clearance in New Zealand has reduced stream channel habitat. A concern regarding riparian planting for stream restoration is that sediment stored in pasture stream banks could be mobilised if grasses are extinguished by shading, resulting in turbid streamwater and sedimentation of fines in the channel.

Records of turtles and sea snakes in New Zealand, 1837–1996 - B. J. Gill (New Zealand Journal of Marine and Freshwater Research, 1997)
Seven species of turtles and sea snakes have reached New Zealand waters. Analysis of 207 records since 1837 shows that the two main species were Dermochelys coriacea and Pelamis platurus , followed by Chelonia mydas . Many marine reptiles probably came from Australian populations and were assisted or carried to New Zealand by the East Australian Current. A peak of records in 1989 coincided with an influx of tropical and subtropical fishes in north‐eastern New Zealand. Nearly 70% of all marine reptile records were between January and May, with few records in winter and spring. Records for D. coriacea declined throughout the year, and the same was true for Ch. mydas except for a secondary peak in October. The summer‐autumn peak in records for these two species may reflect an increased presence or activity during warmer weather. P. platurus occurred mainly from March to May and was absent from August to December, perhaps because no individuals survive after July. Marine reptiles were mostly recorded in the north of the North Island at 34–38°S latitude; only D. coriacea was widely reported further south. None of the turtles measured had carapaces below 375 mm long, except for Caretta caretta for which juveniles as small as 80 mm were recorded. These juveniles may have hatched at the C. caretta breeding grounds in south‐east Queensland. All P. platurus were adults (>500 mm total length) but the smallest Laticauda colubrina was 295 mm. Nearly 70% of turtles, and some 80% of P. platurus , were alive when found. About 45% of turtles were washed ashore when found, and 41% were entangled in nets or lines, whereas 95% of P. platurus were found washed ashore.

Land‐use effects on the hyporheic ecology of five small streams near Hamilton, New Zealand - Andrew J. Boulton; Mike R. Scarsbrook; John M. Quinn; Greg P. Burrell (New Zealand Journal of Marine and Freshwater Research, 1997)
Although the importance of the subsurface saturated interstitial zone (hyporheic zone) to the ecological functioning and maintenance of water quality of stream ecosystems is well known, there is little information on the impacts of different forms of land use upon this zone. Hyporheic physico‐chemistry and invertebrates were compared among small streams draining hill‐country catchments under pasture, exotic pine forest, and native forest near Hamilton, New Zealand. In streams draining native forest, the hyporheic zone harboured a relatively diverse invertebrate fauna comprising mostly taxa common in the surface benthos, although a few apparently obligate hyporheic taxa (ostracods, blind amphipods) were collected. Few individuals and taxa occupied the hyporheic zones of streams draining pasture with some groups such as water mites conspicuously absent. The hyporheos of the stream in exotic pine forest was similar in richness and abundance to that of the pasture streams. Hyporheic water temperatures were significantly higher in the pasture streams than those in pine or native forest. There were strong positive correlations between percentage saturation of dissolved oxygen in the hyporheic zones of all streams and both species richness and total invertebrate abundance. We suggest that land clearance for pasture leads to hill slumping and siltation that bury the lateral bars along the stream channels, rendering this habitat unsuitable for hyporheic invertebrates. Channel narrowing and incision may physically remove further hyporheic habitat, and the reduction of flushing flows to remove interstitial silt and clay leads to low hyporheic dissolved oxygen concentrations and reduced colonisation by surface benthos.

Transports across the Tasman Sea from WOCE repeat sections: The East Australian Current 1990–94 - Stephen M. Chiswell; John Toole; John Church (New Zealand Journal of Marine and Freshwater Research, 1997)
Between March 1990 and March 1994, six cruises were made by Australian, New Zealand, and United States investigators in the Tasman Sea, occupying World Ocean Circulation Experiment repeat hydrographic lines PR11 (30°S) and PR13N (43°S). The northern section was occupied five times, the southern section was occupied four times. All sections measured temperature and salinity from the ocean surface to the bottom. Baroclinic transports through these sections are highly variable, and confirm that there is considerable eddy energy in the East Australian Current. The East Australian Current, when defined to be the main southward flowing branch, has transports varying from 22.2 to 42.2 Sv, although much of this is recirculated. As a result the total transport into the Tasman Sea, between Australia and 173°E, varies from 8.0 to 25.5 Sv. When plotted as a function of season, these transports are well fit by annual‐period sinusoids, suggesting that any interannual variability is aliased by the annual cycle.

Isolation and characterisation of two chymotrypsins from Allocyttus niger (black oreo dory) viscera - Jacek Krzyzosiak; Roy M. Daniel (New Zealand Journal of Marine and Freshwater Research, 1997)
Two serine proteases from the viscera of deep‐sea fish, black oreo dory (Allocyttus niger) , were purified by hydrophobic, affinity, and cation exchange chromatography. They were designated as chymotrypsins on the basis of substrate specificity and susceptibility to inhibitors. The pH optima of chymotrypsin I and II were 8.6 and 10, respectively. Chymotrypsin II retained a remarkable 80% activity at pH 12.5. Thermal stability of both enzymes was enhanced in the presence of calcium ions. Both chymotrypsins were inhibited by high concentrations of substrate Suc‐AAPF‐NA.

Variability in life history characters of the Chilean oyster Tiostrea chilensis (Philippi, 1845) - A. G. Jeffs; S. H. Hooker; R. G. Creese (New Zealand Journal of Marine and Freshwater Research, 1997)
Differences in some life history characters of the Chilean oyster, Tiostrea chilensis , were examined for three populations in the northern North Island of New Zealand. Previous studies of oyster populations in the South Island have predicted that populations at lower latitudes would produce smaller‐sized larvae and substantial numbers of planktonic larvae. For only one northern population was there some evidence of the release of planktonic larvae. However, larvae from all three northern study populations were smaller in size than reported for all other locations, both in New Zealand and Chile. This was because of a trend for larval size to vary inversely with sea water temperature. The results of this study indicate that life history characters of this species can vary greatly at both the individual and population level. Furthermore, this variability does not always conform to commonly proffered life history principles which assert that planktonic development and small larvae become more common at low latitudes.

Epibenthic communities on the Chatham Rise, New Zealand - D. G. McKnight; P. K. Probert (New Zealand Journal of Marine and Freshwater Research, 1997)
Samples of epibenthic macrofauna were collected using a small sledge trawl from 40 stations on the Chatham Rise (42°34′‐44°47′S; 175°34′E‐179°03′W) at water depths of 237–2039 m. 218 taxa were collected, predominantly echinoderms, crustaceans, and molluscs. Multivariate analysis based on 85 species indicated three epibenthic communities, the shallowest characterised mainly by crustaceans and two deeper water communities mainly characterised by echinoderms: (1) a community on predominantly sandy sediments on the crest and shallower flanks of the Rise at 237–602 m that included as characteristic species Munida gracilis, Phylladiorhynchus pusillus, Campylonotus rathbunae, Pontophilus acutirostris , and Acutiserolis bromleyana (Crustacea), Amphiura lanceolata (Ophiuroidea), Cuspidaria fairchildi , and Euciroa galatheae (Bivalvia); (2) a community associated with muddy sediments at 462–1693 m that included Ypsilothuria bitentaculata and Pentadactyla longidentis (Holothuroidea), Brissopsis oldhami (Echinoidea), and Amphiophiura ornata (Ophiuroidea); and (3) a community on muddy sediments at 799–2039 m that included Ophiomusium lymani (Ophiuroidea), Porcellanaster ceruleus (Asteroidea), Gracilechinus multidentatus (Echinoidea), and Aeneator recens (Gastropoda). Bathymetric range of the communities was not symmetrical on either side of the Rise; there was a marked submergence on the north side similar to the vertical displacement of the core of the Antarctic Intermediate Water.

Shade effects on stream periphyton and invertebrates: An experiment in streamside channels - John M. Quinn; A. Bryce Cooper; Morag J. Stroud; Gregory P. Burrell (New Zealand Journal of Marine and Freshwater Research, 1997)
The effects of shade on periphyton and invertebrates were investigated by comparisons in 12 replicate channels beside a pasture stream where shade cloth reduced the photosynthetically available radiation (PAR) by 0, 60, 90, and 98%. Periphytic productivity decreased with increasing shade. Periphyton chlorophyll a was consistently low ( −2 ) under 98 and 90% shade and usually low at 60% shade, whereas blooms were common during summer in the unshaded channels. More periphytic taxa occurred in the open than shaded channels and the relative concentration of the photo‐protective pigment beta‐carotene decreased with increasing shade. Nitrate uptake rates by periphyton, measured in separate chamber studies, decreased progressively as shade increased from 60% through 90% to 98%, and were more strongly correlated with gross primary productivity than periphyton chlorophyll a and particulate carbon levels. Total invertebrate and chironomid densities declined significantly as shade increased from 60 to 90% and invertebrate taxa richness declined markedly between 90 and 98% shade. Most collector‐browsing invertebrates (other than chironomids) had similar densities under 0–90% shade and only declined at 98%. This suggests a weak coupling of these invertebrates with local periphyton production and also suggests that energy derived from up‐stream sources may be their most important food in these pastoral streams.

Land use effects on habitat, water quality, periphyton, and benthic invertebrates in Waikato, New Zealand, hill‐country streams - John M. Quinn; A. Bryce Cooper; Robert J. Davies‐Colley; J. Christopher Rutherford; R. Bruce Williamson (New Zealand Journal of Marine and Freshwater Research, 1997)
Water quality, habitat, and biota were compared during spring amongst c. 100 m reaches on 11 streams draining pasture, native (podocarp‐broadleaf) forest, and exotic pine forest established on pasture 15 years previously. Differences were greatest between the pasture and native forest streams. Only 1–3% of incident light reached native and pine forest streams whereas 30% reached pasture streams. Pasture streams had 2.2°C higher mean temperature than the native streams, and 5‐fold higher nitrate, 30‐fold higher algal biomass, and 11‐fold higher gross photosynthesis. Native streams were 60% wider than pasture, with pine streams intermediate. Pine and pasture streams had 3‐fold higher suspended solids and fine sediment stored in the streambed than native streams. Woody debris volume was 17‐fold greater in pine than pasture streams, with native streams intermediate. Invertebrate taxa richness did not differ between land uses. Community composition differed most between pasture and native forest, with pine forest streams intermediate. Invertebrate densities were 3‐fold higher in pasture than native streams, mainly because of more chironomids and snails, but mayflies, stoneflies, and caddisflies densities were 2–3‐fold higher in forest streams than pasture.

Predicting the effects of shade on water temperature in small streams - J. Christopher Rutherford; Shane Blackett; Colin Blackett; Laurel Saito; Robert J. Davies‐Colley (New Zealand Journal of Marine and Freshwater Research, 1997)
A computer model for stream water temperature was developed, and tested in a small pasture stream near Hamilton, New Zealand. The model quantifies shading by riparian vegetation, hillsides, and stream banks using three coefficients: canopy angle, topography angle, and canopy shade factor. Shade was measured directly and found to vary significantly along the channel. Using the maximum measured shade, a close match was achieved between observed and predicted daily maximum and minimum water and bed sediment temperature. Model predictions of incoming and outgoing long‐wave radiation flux closely matched measurements, but there were unexplained discrepancies in short‐wave radiation flux. Model predictions indicate that moderate shade levels (c. 70%) may be sufficient in temperate climates to restore headwater pasture stream temperatures to 20°C, an estimate of the thermal tolerance for sensitive invertebrates.

Physical characterisation of microform bed cluster refugia in 12 headwater streams, New Zealand - Barry J. F. Biggs; Maurice J. Duncan; Steven N. Francoeur; William D. Meyer (New Zealand Journal of Marine and Freshwater Research, 1997)
Recent sediment transport research has demonstrated that microform bed clusters (MBC) are particularly resistant to entrainment during floods and preliminary biological surveys have shown that such structures could be providing important refugia for benthos in streams. We therefore surveyed MBC in a selection of headwater streams, South Island, New Zealand to determine how common such structures are and then related their occurrence to flow variability, relative armouring, reach gradient, and sediment geology/ geometry to obtain a greater understanding of hydrological and hydraulic stream‐scale factors affecting their density and composition. MBC were present in all streams and ranged in density from 0.067 to 0.279 m −2 . They occupied up to 4.4% of the surface area of the survey reaches, generally had 2–3 particles (a maximum of 7), and the average size for the largest particles ranged from 18.5 to 42.8 cm. MBC density and percentage site cover was significantly related to the relative armouring, but not to flow variability. The number of sediment particles per cluster was significantly correlated with reach gradient, although sediment geology, and associated geometry of particles, also appeared to be important. Thus, density and structure of MBC appeared to be primarily controlled by the interaction of relative armouring and reach gradient with highest densities and the largest number of cluster particles occurring in steep streams with high bed armouring. These structures were sufficiently common to be playing a significant role as flood refugia for benthos in some high gradient, headwater streams.

Microbial enzymatic response to catchment‐scale variations in supply of dissolved organic carbon - Stuart Findlay; Christopher W. Hickey; John M. Quinn (New Zealand Journal of Marine and Freshwater Research, 1997)
A suite of exoenzyme activities was assayed in three New Zealand streams draining pasture, native forest, and a pine catchment. There were differences among catchments in activity of three of the five enzymes assayed (cello‐biohydrolase, N‐acetylglucosaminidase, and dihydroxylphenylalanine oxidation). A principal components analysis (PCA) demonstrates that patterns of enzyme activity can be used to separate the three stream types. An experimental addition of algal‐leachate, leaf‐litter leachate, and high dissolved organic carbon (DOC) water from a small seep also resulted in marked shifts in epilithic enzyme activities 1 day after DOC additions. Oxidative enzymes showed a particularly strong response to additions of humic DOC. As for the field samples, a PCA showed large differences among treatments indicating that exoenzyme patterns can be used to examine which DOC sources predominate in different streams. Application of this approach to describing differences among streams will require detailed seasonal sampling together with longer‐term experiments.

Reserve Selection in a Species‐Rich and Fragmented Landscape on the Agulhas Plain, South Africa - A. T. Lombard; R. M. Cowling; R. L. Pressey; P. J. Mustart (Conservation Biology, 1997)
The Agulhas Plain on the southern tip of South Africa falls within the world’s “hottest” hot‐spot of plant diversity and endemism. Fynbos communities and renoster shrubland form the dominant vegetation types on the plain, but these have been severely fragmented by agriculture, alien plant invasions, and coastal resort development. Most of the vegetation communities are under‐represented within existing protected areas, and most of the land is privately owned. We recommend that a contractual national park, involving both private and public land owners, be established on the plain, and we have developed a reserve‐selection algorithm that provides a flexible tool for selecting representative areas for protection. The algorithm is a stepwise heuristic, with rules for including mandatory areas, forcing adjacency, and excluding undesirable areas. The selection units of the algorithm are 3 × 3 km cells, and the goal of the algorithm is to simultaneously select different target areas ( percentages of total areas) of 11 vegetation types, as well as one population of each of the 99 endemic species, in the smallest area possible. Eight variations of the algorithm were run to provide flexibility in the results. Between 55 and 61 cells (out of a total of 193) were selected, 45 of which were common to all variations. Invoking the adjacency rule, or avoiding alien cells, costs less than 5% extra area. Six of the vegetation types are close to their targets, and the remaining 5 are over‐represented by between 46–166%. Percentage over‐representation is negatively and significantly correlated with percentage target. Between 72–78% of endemic species are represented more than once in the final sets of cells, and the gamma diversity of the Agulhas Plain is incidentally accommodated for. We suggest that the 45 cells common to all algorithm variations form the core of the contractual national park. Final reserve boundaries will differ from those of the selection units, so, as management boundaries are progressively defined, the algorithm can be rerun to account for the changes in the reserved areas of target features. We thus provide a dynamic and flexible tool for reevaluating priorities during the development of a park.

Gap Crossing Decisions by Forest Songbirds during the Post‐Fledging Period - André Desrochers; Susan J. Hannon (Conservation Biology, 1997)
Gaps in forest cover, created by agriculture, forestry, and other anthropogenic activities, are assumed to impede the movements of many forest songbirds. Little is known, however, about the reluctance of different species of birds to cross habitat gaps. We studied this by inducing birds in the post‐fledging period to cross gaps of varying widths and to choose between routes through woodland or across open areas by attracting them to a recording of mobbing calls by Chickadees ( Parus atricapillus). In 278 experiments conducted in boreal forest and agricultural landscapes near Québec city, 157 birds or flocks of birds of five species were attracted. Overall, birds were twice as likely to travel through 50 m of woodland than through 50 m in the open to reach the recording. When given a choice of traveling through woodland or across a gap, the majority of respondents preferred woodland routes, even when they were three times longer than shortcuts in the open. However, species differed greatly in their response to gaps. Our results show that woodland links significantly facilitate movements of birds across fragmented landscapes.

Developing a Sampling Strategy for Baptisia arachnifera Based on Allozyme Diversity - Jennifer F. Ceska; James M. Affolter; J. L. Hamrick (Conservation Biology, 1997)
We analyzed the amount and distribution of genetic variation in Baptisia arachnifera Duncan to develop a sampling strategy for ex situ research. Baptisia arachnifera is an endangered plant species endemic to the coastal plain of Georgia (U.S.) where all populations are within 16 km of each other. A reduction in numbers of individuals has been observed during the last 50 years. Baptisia arachnifera was polymorphic at 24% of the 37 loci examined with an average of 1.32 alleles per locus. The genetic diversity index was relatively low ( H e = 0.097) as expected for endemic species. Populations were in Hardy‐Weinberg equilibrium, suggesting that the species is outcrossing. Consistent with this conclusion is the observation that the majority (approximately 90%) of the genetic variation present in the species is found within individual populations. Indirect evidence of gene flow between populations was detected ( Nm = 2.35). The close proximity of the populations and the recent reduction in population sizes suggest that the populations surveyed may be fragments of a once more continuous gene pool. Based on the observed distribution of genetic diversity among populations (G ST = 0.096), sampling two populations would capture 99% of the allozyme diversity surveyed. Allozyme data were used to determine which 2 of the 10 populations surveyed should be sampled to maximize the ex situ conservation of genetic diversity. Although the paper‐producing companies that own most of the land where Baptisia arachnifera occurs are modifying their harvesting techniques, the species could become extinct without more effective management and preservation efforts.

Is Mutation Accumulation a Threat to the Survival of Endangered Populations? - Dean M. Gilligan; Lynn M. Woodworth; Margaret E. Montgomery; David A. Briscoe; Richard Frankham (Conservation Biology, 1997)
The accumulation of new deleterious mutations has been predicted to constitute a significant threat to the survival of finite sexually reproducing populations. Three measures of genetic load were made on populations of Drosophila melanogaster maintained at effective population sizes of 25, 50, 100, 250, and 500 for 45 or 50 generations and their outbred base population and a new sample from the same wild population. Genetic loads were measured as fitness differentials between inbred and non‐inbred lines derived from each population under both benign ( productivity of single pairs) and competitive (competitive index) conditions. No trend of smaller populations exhibiting greater genetic loads than larger ones was observed under either benign or competitive conditions. Further, genetic loads were similar in captive and wild populations. Frequencies of deleterious and lethal alleles on chromosome II were measured by making the chromosome (approximately 40% of the genome) homozygous using a marked balancer stock. Neither deleterious nor lethal allele frequencies exhibited a relationship with population size. The accumulation of detrimental mutations does not appear to pose a significant threat to finite sexual populations with effective sizes of 25 or more over the 100–200 year time frames considered in most wildlife conservation programs.

Goat Eradication on Isabella Island - Bruce E. Coblentz (Conservation Biology, 1997)

Effects of Rock Climbing on Populations of Presettlement Eastern White Cedar ( Thuja occidentalis ) on Cliffs of the Niagara Escarpment, Canada - P. E. Kelly; D. W. Larson (Conservation Biology, 1997)
Cliffs of the Niagara Escarpment support a self‐sustaining presettlement forest of eastern white cedar ( Thuja occidentalis L.) in which some trees are over 1000 years old. Many of the cliffs are also popular locations for recreational rock climbing. Our study employed a stratified random sampling design to assess the impact of rock climbing on populations of cliff‐face and cliff‐edge trees. Tree density and age structure were compared between four climbed and three unclimbed sites in the vicinity of Milton, Ontario. Signs of physical damage were also recorded for the trees sampled at each site. The results showed that living tree density on the cliff face was lower in climbed areas. The age structures of these forests showed that the numbers of older and younger age classes have been reduced on climbed cliff faces compared with unclimbed areas. A high percentage of trees on climbed cliff faces showed evidence of damage by humans. These trends were not as apparent on cliff edges where other disturbances have affected age structure. We recommend that cliff faces be explored for the presence of presettlement forest and that recreation managers of lands with exposed cliff faces incorporate rock climbing considerations into their management plans. Monitoring programs would help track levels of disturbance. Education of the climbing community would be the most effective long‐term solution to limiting disturbance in sensitive areas.

Genetic Structure and Migration in Native and Reintroduced Rocky Mountain Wolf Populations - Stephen H. Forbes; Diane K. Boyd (Conservation Biology, 1997)
Gray wolf (Canis lupus) recovery in the Rocky Mountains of the U.S. is proceeding by both natural recolonization and managed reintroduction. We used DNA microsatellite analysis of wolves transplanted from Canada to two reintroduction sites in the U.S. to study population structure in native and reintroduced wolf populations. Gene flow due to migration between regions in Canada is substantial, and all three recovery populations in the U.S. had high genetic variation. The reintroduced founders were moderately genetically divergent from the naturally colonizing U.S. population. These findings corroborate that the reintroduction more than meets generally accepted genetic guidelines. Maintaining this variation, however, will depend on ample reproduction in the first few generations. In the long term genetic variation will best be retained if migration occurs among the recolonizing and the two transplanted populations. Evidence from field observation and genetic studies shows extensive dispersal by wolves, and we conclude that exchange among these groups due to natural dispersal is likely if public tolerance and legal protection are adequate outside lands designated for wolf recovery.

Diamondback Terrapin ( Malaclemys terrapin) Mortality in Crab Pots - Willem M. Roosenburg; William Cresko; Michael Modesitte; Matthew B. Robbins (Conservation Biology, 1997)
The entrapment of diamondback terrapins ( Malaclemys terrapin) in crab pots frequently results in drowning and death of the trapped turtles. We determined the rate of capture, size, sex, and age of terrapins captured, and the potential impact crab pot mortality has on local terrapin populations. We estimated terrapin capture rates of 0.17 terrapins/pot/day in shallow water areas of Chesapeake Bay (Maryland, USA). The sex ratio of terrapins caught in crab pots was 3:2 male biased because female terrapins become too large to enter crab pots by the time they reach 8 years of age. Males, however, remain vulnerable to entrapment throughout their life. Our estimates of capture rates and local population size suggest that 15–78% of a local population may be captured in a single year. As a consequence, crab pots may be the major reason terrapins are extirpated in coastal, shallow water areas with heavy crab pot fisheries. Additionally, the selective removal of males may also contribute to female‐biased sex ratios observed in this diamondback terrapin population. We developed and tested a modified crab pot that increases terrapin survival and does not reduce the number of crabs caught. Our modified crab pot maintained permanent access to air and prevented the drowning of terrapins. Additionally, our modified crab pot caught more crabs than standard commercial crab pots, suggesting that the modified crab pot could be a viable alternative to standard traps that result in terrapin mortality.

Effects of Motorized Tourboats on the Behavior of Nonbreeding American Flamingos in Yucatan, Mexico - Eduardo Galicia; Guy A. Baldassarre (Conservation Biology, 1997)
We assessed the effect of motorized tourboats on the behavior of nonbreeding American flamingos ( Phoenicopterus ruber ruber) in the Celestún Estuary, a Special Biosphere Reserve in Yucatán, Mexico, from November 1994 through February 1995. We measured these effects by comparing activity budgets between flocks of flamingos disturbed and undisturbed by tourboats. Disturbance reduced feeding time from 40% before disturbance to 24% after, a 40% loss. Boat disturbance increased alert behavior by 400%. Tourboats averaged 13 per day and caused a disturbance 75% of the time or 3.3 hours per day. Potential loss of feeding time for individuals was estimated at 13% but is likely much higher on days with excessive numbers of tourboats. Flamingos returned to normal feeding rates (40%) within 20 minutes after disturbance. Most tourists (52%) were from Mexico, followed by Germany (14%), and 88% of Mexican visitors were willing to pay an entrance fee to the Celestún Reserve. Conservation efforts should focus on education of tourboat operators to reduce disturbance to flamingos, education of tourists through a visitor’s center and brochures produced in Spanish and English, and expanded involvement of local people.

Managing Stand Structure as Part of Ecologically Sustainable Forest Management in Australian Mountain Ash Forests - David B. Lindenmayer; Jerry F. Franklin (Conservation Biology, 1997)
Ecologically sustainable management of temperate forests is a complex task that involves balancing potentially conflicting land uses such as wood production and nature conservation. We argue that a variety of strategies implemented at different spatial scales is required for biodiversity conservation in temperate forests where wood production is permitted. This is a form of “risk‐spreading;” if one option is ineffective for a given species, it may still be conserved as a result of the implementation of other approaches. At the largest scale, there is a clear need for reserves to protect representative samples of forest ecosystems. Within landscapes broadly designated for timber harvesting, intermediate‐scale strategies such as the implementation of networks of streamside reserves and wildlife corridors are important for biodiversity conservation. At smaller spatial scales within harvested areas, critical habitat components for forest‐dependent organisms like large old trees and logs must be provided. We focus on the importance of these fine‐scale attributes for the conservation of biodiversity within logged forests using the mountain ash ( Eucalyptus regnans) forests of the Central Highlands of Victoria as a case study. Forest managers must develop silvicultural practices that maintain and perpetuate critical stand attributes essential for the conservation of forest‐dependent organisms. To this end, a shift is required from the extensive use of clearfelling to the adoption of new silvicultural techniques that maintain more structurally complex multi‐aged stands. The maintenance of key structural features should be used as a template to guide harvesting methods to ensure that production forests contribute to biodiversity conservation, not only in mountain ash forests, but also temperate wood production elsewhere around the world.

The Use by Rain Forest Mammals of Natural Forest Fragments in an Equatorial African Savanna - C. E. G. Tutin; L. J. T. White; A. Mackanga‐Missandzou (Conservation Biology, 1997)
Two contrasting vegetation types occur in the Lopé Reserve in central Gabon: tropical rain forest dominates but areas of savanna containing natural forest fragments also exist. How forest mammals use the forest fragments has broad implications for conservation and management of tropical ecosystems because the natural landscape at Lopé mimics the fragmentation of forests produced increasingly by human action. The Lopé savannas result from climate induced vegetation changes over the past 20,000 years and are currently maintained by active management because, without regular burning, they are colonized by forest. Forty‐five species of large mammal (body weight ≥2 kg ) have been recorded at Lopé and, although none are savanna specialists, some use the savanna habitat. Sweep censuses were conducted monthly over 2 years in 13 forest fragments. The census sites were small (0.4–11 ha), completely or largely surrounded by savanna, and up to 450 m from continuous rain forest. Population density and biomass were calculated for the 26 species of mammals encountered (nocturnal species were rarely seen) and compared to data previously collected in adjacent continuous forests. Total biomass (6010 kg km −2 ) was highest in the forest fragments. Compared to adjacent, continuous forest, elephants ( Loxodonta africana) were less common whereas buffalo (Syncerus caffer) and red river hog ( Potamochoerus porcus) were much more numerous. Of eight species of diurnal primates, four were more common, two occurred at similar densities, and two were much less common in the fragmented habitat. Most mammalian species moved between continuous forest and the fragments but two species of guenon and six species of duiker appeared to reside permanently in some fragments. The diversity and high biomass of large mammals found within the forest outliers at Lopé is surprising and suggests that fragmentation per se will not be catastrophic for most of these species.

Species Richness, Endemism, and the Choice of Areas for Conservation - Jeremy T. Kerr (Conservation Biology, 1997)
Although large reserve networks will be integral components in successful biodiversity conservation, implementation of such systems is hindered by the confusion over the relative importance of endemism and species richness. There is evidence ( Prendergast et al. 1993) that regions with high richness for a taxon tend to be different from those with high endemism. I tested this finding using distribution and richness data for 368 species from Mammalia, Lasioglossum, Plusiinae, and Papilionidae. The study area, subdivided into 336 quadrats, was the continuous area of North America north of Mexico. I also tested the hypothesis that the study taxa exhibit similar diversity patterns in North America. I found that endemism and richness patterns within taxa were generally similar. Therefore, the controversy over the relative importance of endemism and species richness may not be necessary if an individual taxon were the target of conservation efforts. I also found, however, that richness and endemism patterns were not generally similar between taxa. Therefore, centering nature reserves around areas that are important for mammal diversity (the umbrella species concept) may lead to large gaps in the overall protection of biodiversity because the diversity and endemism of other taxa tend to be concentrated elsewhere. I investigated this further by selecting four regions in North America that might form the basis of a hypothetical reserve system for Carnivora. I analyzed the distribution of the invertebrate taxa relative to these regions and found that this preliminary carnivore reserve system did not provide significantly different protection for these invertebrates than randomly selected quadrats. I conclude that the use of Carnivora as an umbrella taxon is an unreliable method for invertebrate conservation.

. (Conservation Biology, 1997)

Noah Worked Two Jobs - J. Michael Scott Thinsp; Blair Csuti (Conservation Biology, 1997)

Insular Endemic Plants Lack Defenses Against Herbivores - Lizabeth Bowen; Dirk Van Vuren (Conservation Biology, 1997)

The Application of Neutral Landscape Models in Conservation Biology - Kimberly A. With (Conservation Biology, 1997)
Neutral landscape models, derived from percolation theory in the field of landscape ecology, are grid‐based maps in which complex habitat distributions are generated by random or fractal algorithms. This grid‐based representation of landscape structure is compatible with the raster‐based format of geographical information systems (GIS), which facilitates comparisons between theoretical and real landscapes. Neutral landscape models permit the identification of critical thresholds in connectivity, which can be used to predict when landscapes will become fragmented. The coupling of neutral landscape models with generalized population models, such as metapopulation theory, provides a null model for generating predictions about population dynamics in fragmented landscapes. Neutral landscape models can contribute to the following applications in conservation: (1) incorporation of complex spatial patterns in (meta)population models; (2) identification of species’ perceptions of landscape structure; (3) determination of landscape connectivity; (4) evaluation of the consequences of habitat fragmentation for population subdivision; (5) identification of the domain of metapopulation dynamics; (6) prediction of the occurrence of extinction thresholds; ( 7) determination of the genetic consequences of habitat fragmentation; and (8) reserve design and ecosystem management. This generalized, spatially explicit framework bridges the gap between spatially implicit, patch‐based models and spatially realistic GIS applications which are usually parameterized for a single species in a specific landscape. Development of a generalized, spatially explicit framework is essential in conservation biology because we will not be able to develop individual models for every species of management concern.

Correlates of Amphibian Diversity in an Altered Landscape of Amazonian Ecuador - Peter B. Pearman (Conservation Biology, 1997)
There is disagreement on the effects of logging and habitat alteration on amphibians and few studies have addressed this issue in tropical forests. I addressed whether the habitat variation associated with logging and agriculture is correlated with the species richness and community structure in an assemblage of amphibians in the Tropical Wet Forest life zone in Amazonian Ecuador. I evaluated 10 variables describing environmental variation and forest structure at 23 0.5‐ha sites and sampled amphibians using nocturnal visual searches of transects. Overall amphibian species richness increased weakly with distance to pasture but taxa differed in correlates of diversity. Species richness in the genus Eleutherodactylus increased markedly with distance to pasture. Eleutherodactylus species richness was highest at intermediate values of stand basal area, which contributed to my detecting only weak differences in species richness between primary and selectively logged sites. Overall, distance to pasture, basal area, and understory density explained much of the variation in Eleutherodactylus species richness. In contrast to Eleutherodactylus, species richness of hylid frogs was relatively greater in sites with low basal area, predominantly in selectively‐logged forest. Patterns of amphibian species richness poorly represented eleutherodactyline frogs because the absence of Eleutherodactylus from disturbed sites was sometimes masked by increasing richness of disturbance‐tolerant species. Canonical correspondence analysis indicated that species occurrence varied with measured environmental variation; some species distinctly prefer less‐disturbed forest. The generality of these patterns should be confirmed in additional studies. The results suggest that overall amphibian richness is not a good indicator of conservation value for disturbance‐sensitive eleutherodactylines, which are nocturnal, rare, and difficult to identify. Elutherodactylines in Tropical Wet Forest provide a good opportunity for the development of indicator relationships for the conservation of a disturbance‐sensitive assemblage. The mechanisms that result in the patterns of diversity described here are unknown and warrant further study. These observations, and the quantitative relationships developed here, suggest the use of empirical environment/diversity relationships for preliminary assessment of tropical amphibian diversity and in predicting the effects of forest management on disturbance‐sensitive species.

Population Genetic Structure in the Black Rat Snake: Implications for Management - K. A. Prior; H. L. Gibbs; P. J. Weatherhead (Conservation Biology, 1997)
Assessments of population genetic structure and diversity can be of value in formulating management plans for threatened species. Using randomly amplified polymorphic DNA markers, we found evidence of significant genetic structure among black rat snakes ( Elaphe obsoleta) sampled at three spatial scales. Highly isolated (1500–1900 km apart) populations were strongly divergent ( F ST = 0.242–0.323), whereas populations more proximal ( 465 km apart) although currently isolated, exhibited far less divergence ( F ST = 0.019). A considerable proportion (80%) of total genetic diversity was due to differences among individuals within populations, although differences among populations (8%) also were significant. At the scale of sub‐populations ( local populations 15–50 km apart), differentiation was generally moderate ( F ST = 0.058). Our estimates of Nei’s genetic distance for sub‐populations (0.014) approximated (mean = 0.044) those obtained in other studies that have assessed differentiation between snake populations based on variation in allozymes. The majority (ca. 86%) of total genetic variance across five sub‐populations was attributable to differences among individuals, although differences among sub‐populations (ca. 13%) also were significant. We found little evidence of genetic structure ( F ST = 0.006) between pairs of hibernacula, our finest spatial scale (samples 1–2 km apart), if they were located in natural habitats. In contrast, a pair of hibernacula sampled in an urban area exhibited genetic structure equivalent to some sub‐population differences ( F ST = 0.039), suggesting interrupted gene flow related to urban development. Our results have direct implications for ranking populations in terms of their conservation value and the genetic management of threatened snakes.

Threats to Imperiled Freshwater Fauna - Brian D. Richter; David P. Braun; Michael A. Mendelson; Lawrence L. Master (Conservation Biology, 1997)
Threats to imperiled freshwater fauna in the U.S. were assessed through an experts survey addressing anthropogenic stressors and their sources. Specifically, causes of historic declines and current limits to recovery were identified for 135 imperiled freshwater species of fishes, crayfishes, dragonflies and damselflies, mussels, and amphibians. The survey was designed to identify threats with sufficient specificity to inform resource managers and regulators faced with translating information about predominant biological threats into specific, responsive actions. The findings point to altered sediment loads and nutrient inputs from agricultural nonpoint pollution; interference from exotic species; and altered hydrologic regimes associated with impoundment operations as the three leading threats nationwide, accompanied by many lesser but still significant threats. Variations in threats among regions and among taxa were also evident. Eastern species are most commonly affected by altered sediment loads from agricultural activities, whereas exotic species, habitat removal/damage, and altered hydrologic regimes predominate in the West. Altered sediment loading from agricultural activities and exotic species are dominant problems for both eastern mussels and fishes. However, eastern fishes also appear to be suffering from municipal nonpoint pollution (nutrients and sediments), whereas eastern mussels appear to be more severely affected by altered nutrient impacts from hydroelectric impoundments and agricultural runoff. Our findings suggest that control of nonpoint source pollution associated with agriculture activities should be a very high priority for agricultural producers and governmental support programs. Additonally, the large number of hydropower dams in the U.S. subject to federal re‐licensing in coming years suggests a significant opportunity to restore natural hydrologic regimes in the affected rivers.

The Use of Bushland, Corridors, and Linear Remnants by Birds in Southeastern Queensland, Australia - Jocelyn M. Bentley; Carla P. Catterall (Conservation Biology, 1997)
Within the southeastern region of Queensland, Australia, native forest cover ( bushland) has been greatly reduced and fragmented, and clearing is still occurring. Many of the region’s bird species are being increasingly restricted to isolated habitat remnants. However, little is known about the habitat value of these remnants and whether their value is influenced by their degree of connection. We investigated bird use of riparian corridors in pastoral and urban surroundings and riparian linear remnants within an urban context. We compared the avifauna of these remnants with dryland and riparian sites within continuous bushland. We also assessed their use by previously derived response‐guilds of birds to bushland clearing. We counted 3567 individuals of 102 bird species. Riparian bushland supported more species and had greater bird abundances than dryland bushland. Corridors and linear remnants supported densities of many bushland‐dependent species similar to those in bushland; this varied with species’ patterns of large‐scale migration and residency. Bushland‐dependent winter migrants used both corridors and linear remnants extensively. Bushland‐dependent residents were most abundant in continuous bushland and least abundant in linear remnants, possibly reflecting the constraints of central place foraging. Effects of isolation were only evident in resident bushland‐dependent species. Local habitat variables were significantly associated with variation in abundance of some types of birds within corridors and linear remnants; however, the differences in bird abundances attributable to spatial characteristics were greater than those attributable to habitat characteristics. The effects of bushland fragmentation and isolation were mediated by the extent to which species are dependent upon bushland and their patterns of large‐scale migration or residency. Local habitat, and possibly more importantly altitude, may influence site use by winter migrants and generalist species.

Effects of Argentine Ants on Invertebrate Biodiversity in Northern California - Kathleen G. Human; Deborah M. Gordon (Conservation Biology, 1997)

Seeking Balance in Higher Education - Hayden T. Mattingly (Conservation Biology, 1997)

Molecular Genetic Consequences of a Population Bottleneck Associated with Reintroduction of the Mauna Kea Silversword ( Arg yroxiphium sandwicense ssp. sandwicense [Asteraceae]) - Robert H. Robichaux; Elizabeth A. Friar; David W. Mount (Conservation Biology, 1997)
The endangered Mauna Kea silversword (Argyroxiphium sandwicense ssp. sandwicense) has experienced a severe decline in distribution and abundance because of predation by alien ungulates. By the late 1970s only a small remnant natural population persisted on the Mauna Kea volcano on the Island of Hawaii. The Hawaii Department of Land and Natural Resources, Division of Forestry and Wildlife, initiated an outplanting program in the 1970s to promote recovery of A. sandwicense ssp. sandwicense. Intermittent outplanting since 1973 has generated an outplanted population of over 450 plants on Mauna Kea, but the program has unintentionally resulted in a major population bottleneck. All plants in the outplanted population appear to be first‐ or subsequent‐generation offspring of only two maternal founders from the natural population. Genetic variation in the natural and outplanted populations was assessed for 90 random amplified polymorphic DNA loci. Eleven loci were detectably polymorphic in the natural population, whereas only three loci were detectably polymorphic in the outplanted population. Thus, the population bottleneck has been accompanied by a 73% reduction in the level of detectable polymorphism. In addition, for eight loci, the population bottleneck has resulted in the loss of the marker allele in the outplanted population. A management strategy involving manual pollen transfer has recently been implemented to incorporate additional founders from the natural population into the outplanting program. As a supplement to the outplanting program, the strategy also includes a program promoting direct seedling establishment following manual pollen transfer. Incorporating additional founders may serve to overcome the legacy of the population bottleneck, especially if founder representation can be equalized.

Enough Already! - Philip Cafaro; Nicholas Brokaw; Samuel J. McNaughton; Francis E. Putz; Richard E. Bodmer (Conservation Biology, 1997)

The Conservation Biologist as Zen Student - Fred W. Allendorf (Conservation Biology, 1997)

Invasibility and Effects of Amur Honeysuckle in Southwestern Ohio Forests - Todd F. Hutchinson; John L. Vankat (Conservation Biology, 1997)
The Asian exotic Amur honeysuckle ( Lonicera maackii [Rupr.] Herder) has become the dominant shrub in many forests in southwestern Ohio and in some other locations in the eastern United States. Our research focused on the invasibility of forest communities and relationships of L. maackii to the abundance of tree seedlings and herbs. We surveyed 93 forest stands near Oxford, Ohio (USA) to determine L. maackii cover, time since invasion, tree canopy cover, tree basal area, and a shade tolerance index. Stepwise multiple regression indicated that greater than one‐half of the variation (r 2 = 0.550) in Lonicera cover was correlated to five variables (in descending order of importance): tree canopy cover, distance from Oxford, shade tolerance index, tree basal area, and time since invasion. The results suggest that high light levels and proximity to an abundant seed source increase forest invasibility. Tree seedling density, species richness of seedlings, and herb cover were all inversely related to L. maackii cover. When Lonicera becomes abundant, future structure and composition of forests could be affected and local populations of herbs threatened.

Flood and velocity effects on periphyton and silt accumulation in two New Zealand rivers - Ian G. Jowett; Barry J. F. Biggs (New Zealand Journal of Marine and Freshwater Research, 1997)
Effects of water velocity on the accumulation of periphyton and silt were investigated in two unenriched rivers (Tongariro and West Kowai Rivers) of New Zealand. Artificial substrata were incubated for up to 5 weeks in areas of moderate (0.2–0.5 m s −1 ) and high (0.6–0.9 m s −1 ) velocity. In the Tongariro River, periphyton accrual was significantly higher in moderate velocities than in high velocities, but not in the West Kowai River. The accumulation of silt was significantly higher under the moderate velocity treatment in both rivers. Silt densities were closely correlated with periphyton chlorophyll a and stepwise multiple regression analysis indicated that periphyton biomass was a more significant determinant of silt densities than water velocity. Neither chlorophyll a nor silt densities showed any significant variation with depth within the ranges measured (0.2–0.6 m). Several floods occurred during the study period and these, together with water velocities greater than c. 0.3 m s −1 , tended to affect periphyton ash‐free dry mass (AFDM) and silt more than they affected chlorophyll a. It appeared that growing periphyton were resisting the effects of high shear stress and that unattached inorganic and organic particles were flushed from the periphyton matrix during higher flows. Spatial variation in periphyton and silt accrual as functions of velocity and depth were too variable to be useful for prediction of abundance and distribution using hydraulic‐habitat models.

Foraminiferal associations in Wanganui Bight and Queen Charlotte Sound, New Zealand - Bruce W. Hayward; Hugh Grenfell; Catherine Reid (New Zealand Journal of Marine and Freshwater Research, 1997)
Eight benthic foraminiferal associations are recognised in Wanganui Bight and Queen Charlotte Sound, New Zealand, based on cluster analysis of census data from 52 sediment samples. Distribution of the four associations in Wanganui Bight correlates with increasing water depth: Elphidium charlottense/Haynesina depressula/ Patellinella inconspicua association (17–27 m); Patellinella inconspicua/ Quinqueloculina suborbicularis association (20–42 m); Cassidulina carinata/Miliolinella subrotundata association (42–66 m); and Cassidulina carinata/Bulimina submarginata (72–109 m). The four associations in Queen Charlotte Sound are: Quinqueloculina seminula/Elphidium advenum/Haynesina depressula in sandy shallows (0.5–7 m); Epistominella vitreal Haynesina depressula in shallows of the outer Sound (4–12 m); Elphidium vellai/Haynesina depressula in the mouth of the Sound (9–25 m); and Nonionella flemingi/ Notorotalia finlayi in a muddy, sheltered basin (25–42 m). The most important physical factors influencing benthic foraminiferal distribution patterns in these two areas appear to be the characteristics of the water (e.g., temperature, turbidity, salinity) and factors that vary with water depth (e.g., wave and current energy, substrate, light penetration, food availability). Species diversity (α, H) and the relative abundance of planktic foraminiferal tests are mostly greater in the open sea conditions of Wanganui Bight than in Queen Charlotte Sound. In Wanganui Bight both generally increase with increasing depth, although there is a local diversity peak at 70–80 m depth.

Leaf breakdown and colonisation by invertebrates in a headwater stream: Comparisons of native and introduced tree species - S. M. Parkyn; M. J. Winterbourn (New Zealand Journal of Marine and Freshwater Research, 1997)
Leaf breakdown, colonisation by invertebrates, food choice by a facultative shredder, and composition and activity of the microflora of leaves of three native and three introduced trees were investigated in a small headwater stream, South Island, New Zealand. Leaves of each species were immersed and collected after 1, 32, 60, and 95 days to measure mass loss and invertebrate colonisation. Additional leaves collected after 60 days were used for food choice and respiration experiments, and others taken after 95 days (some species) were examined with scanning electron microscopy. Leaf breakdown rates followed the sequence: elm > red beech > willow > mahoe > oak > mountain beech. Elm (introduced) and mahoe (native) supported the highest invertebrate densities, but shredders were most abundant on willow (introduced) and red beech (native) leaves. In laboratory choice trials the facultative shredder Olinga jeanae showed a preference for elm and red beech leaves which were fastest to break down and had high respiration rates. We found that leaves of introduced trees can be preferred by shredders and hence, no strong associations were apparent between shredders and these native trees.

The Sustainability of Subsistence Hunting in the Neotropics - Michael S. Alvard; John G. Robinson; Kent H. Redford; Hillard Kaplan (Conservation Biology, 1997)
Hunting is an important component of native subsistence strategies in Amazonia. It is also a serious threat to biodiversity in some areas. We present data on the faunal harvests of two native Neotropical subsistence hunting peoples, Machiguenga bow‐hunters and Piro shotgun hunters of Peru. The rate of annual harvest per square kilometer of catchment is estimated and compared to rates of sustainable harvest calculated by Robinson and Redford (1991). We used indicators of prey abundance to test for the depletion of species that hunters killed in numbers greater than what the model predicts to be sustainable. As predicted, we found the strongest evidence for local depletion of the large primates at the Piro site. The woolly monkey ( Lagothrix lagothricha) harvest at the Machiguenga village and the deer ( Mazama americana) and collared peccary (Tayassu tajacu) harvests at both sites were not predicted to be unsustainable and we found no evidence for depletion. Machiguenga bow hunters killed spider monkeys (Ateles paniscus) in quantities that were slightly above what the model predicted to be sustainable, yet we found no evidence for depletion. Differential species vulnerability, catchment size, and consumer population size could be important factors in determining sustainability.

The Influence of Model Structure on Conclusions about the Viability and Harvesting of Serengeti Wildebeest - Miguel A. Pascual; Peter Kareiva; Ray Hilborn (Conservation Biology, 1997)
We investigate how the viability and harvestability predicted by population models are affected by details of model construction. Based on this analysis we discuss some of the pitfalls associated with the use of classical statistical techniques for resolving the uncertainties associated with modeling population dynamics. The management of the Serengeti wildebeest (Connochaetes taurinus) is used as a case study. We fitted a collection of age‐structured and unstructured models to a common set of available data and compared model predictions in terms of wildebeest viability and harvest. Models that depicted demographic processes in strikingly different ways fitted the data equally well. However, upon further analysis it became clear that models that fit the data equally well could nonetheless have very different management implications. In general, model structure had a much larger effect on viability analysis (e.g., time to collapse) than on optimal harvest analysis (e.g., harvest rate that maximizes harvest). Some modeling decisions, such as including age‐dependent fertility rates, did not affect management predictions, but others had a strong effect (e.g., choice of model structure). Because several suitable models of comparable complexity fitted the data equally well, traditional model selection methods based on the parsimony principle were not practical for judging the value of alternative models. Our results stress the need to implement analytical frameworks for population management that explicitly consider the uncertainty about the behavior of natural systems.

Noninvasive Physiological Measures of Disturbance in the Northern Spotted Owl - Samuel K. Wasser; Kenneth Bevis; Gina King; Eric Hanson (Conservation Biology, 1997)

Conservation Genetics of North American Freshwater Mussels Amblema and Megalonaias - Margaret Mulvey; Charles Lydeard; Debra L. Pyer; Kimberly M. Hicks; Jayne Brim‐Box; James D. Williams; Robert S. Butler (Conservation Biology, 1997)
Freshwater bivalves are among the most endangered groups of organisms in North America. Efforts to protect the declining mussel fauna are confounded by ambiguities associated with recognition of distinct evolutionary entities or species. This, in part, is due to the paucity of reliable morphological characters for differentiating taxa. We have employed allozymes and DNA sequence data to search for diagnosably distinct evolutionary entities within two problematic genera of unionid mussels, Amblema and Megalonaias. Within the genus Amblema three species are recognized based on our DNA sequence data for the mitochondrial 16S rRNA and allozyme data (Amblema neislerii, A. plicata, and A. elliotti). Only one taxonomically distinct entity is recognized within the genus Megalonaias—M. nervosa. Megalonaias boykiniana of the Apalachicolan Region is not diagnosable and does not warrant specific taxonomic status. Interestingly, Megalonaias from west of the Mississippi River, including the Mississippi, exhibited an allozyme and mtDNA haplotype frequency shift suggestive of an east‐west dichotomy. The results of this study eliminate one subspecies of Amblema and increase the range of A. plicata. This should not affect the conservation status of “currently stable” assigned to A. plicata by Williams et al. (1993). The conservation status of A. elliotti needs to be reexamined because its distribution appears to be limited to the Coosa River System in Alabama and Georgia.

Lack of Evidence for Epidemic Disease as an Agent in the Catastrophic Decline of Australian Rain Forest Frogs - Ross A. Alford; Stephen J. Richards (Conservation Biology, 1997)

Sea Otter Mortality Estimated from Carcasses Collected after the Exxon Valdez Oil Spill - David L. Garshelis (Conservation Biology, 1997)
Large numbers of sea otters ( Enhydra lutris) died following the 1989 Exxon Valdez oil spill. Two previous studies estimated spill‐related mortality, one from the difference between counts of otters before and after the spill, and the other from the recovery rate of tagged carcasses that had been released at sea. I used a derivative of the second approach, but revised it to account for (1) moribund otters that had hauled out on shore; (2) carcasses that were collected at sea; and (3) differences in search effort in different areas of the spill—considerations that were not addressed previously. The mortality estimation procedure presented here, and applied to Prince William Sound, Alaska, had six input parameters, two with fixed values (the number of spill‐related carcasses collected [391] and the number of otters taken alive that died in captivity [84]) and four that were assigned a range of values (the recovery rate for carcasses on the beach [60–90%], the proportion of recovered carcasses that were onshore [70–95%]), the proportion of offshore deaths recovered onshore (20–50%), and the proportion of moribund otters that hauled out (20–60%). Empirical estimates for these parameters were not available after the spill, but a range of plausible values for each was delimited using other available data. Randomly‐selected combinations of values within these ranges produced mortality estimates for the sound ( x¯= 750, 5–95% quantiles ≈ 600–1000) that were lower than indicated by previous studies. These lower estimates do not diminish the tragic nature of the mortality, but instead highlight the significance of both the process and informational basis in producing estimates of catastrophic loss. Estimates of loss based on faulty or inadequate data may mislead investigations of population recovery and may jeopardize public trust in scientific assessments of future catastrophes.

Disappearance and Return of Plethodontid Salamanders to Clearcut Plots in the Southern Blue Ridge Mountains - Andrew N. Ash (Conservation Biology, 1997)
The disappearance and return of plethodontid salamanders on clearcuts has been monitored since 1979 in the southern Blue Ridge Mountains at three sites near Highlands, North Carolina. Salamander abundance on 225 m 2 plots located on clearcuts and in nearby forest was determined by nightly non‐destructive searches. Abundances on clearcut and forest plots at a given site were compared for each year in which sampling occurred. Numbers of salamanders on clearcut plots decreased to 30–50% of forested plots in the first year after logging and were almost zero by the second year. Decreases in standing crop and moisture content of leaf litter seem responsible for salamander disappearance. Salamanders returned to clearcuts 4–6 years after cutting, and their numbers increased rapidly. Linear regressions estimate that salamander numbers on clearcut plots will equal or exceed numbers on forested plots by 20–24 years after cutting. The pattern of salamander return to clearcuts appears closely correlated with the timing of litter layer reformation. All sex and age classes of the most common species, Plethodon jordani, disappear from clearcuts at equal rates, whereas the earliest colonizers are predominantly large adults. Plethodon oconaluftee, a desiccation‐resistant species, exists on regenerating clearcuts in disproportionately large numbers. Large adults of all species, including Plethodon oconaluftee, may be better able to withstand the drier, sparse litter cover of young, regenerating stands. Adults might move to clearcuts to avoid competition from smaller and immature salamanders restricted to mature forests with abundant, moist litter.

Conservation Implications of Host Use for Rare Parasitic Plants - Michelle A. Marvier; David L. Smith (Conservation Biology, 1997)
Both the study and management of parasites have historically focused on the control, and even elimination, of parasite populations. In contrast, rare parasitic plants represent an uncommon challenge for conservation biologists and managers who often wish to bolster populations of these parasites. Although parasitic plants may suffer any of the maladies known to affect small populations of plants, parasitic plants may also be limited by the additional suite of factors of host availability, host quality, host resistance to parasitism, and parasite preference. We describe studies that have examined parasite growth and reproductive performance with a variety of host species to argue that consideration of the host needs of parasitic plants is necessary for successful conservation of rare species using this mode of resource acquisition. Although it is clear that parasite performance varies greatly with the availability of different host species, little is known about the host requirements of most parasitic plants, and the relative importance of particular host species may not immediately be obvious. Further, because published host lists generally do not distinguish minor hosts from those that sustain parasite populations, such lists may be misleading for conservation efforts. We argue that successful conservation and restoration of parasitic plants may necessitate the management of thoughtfully selected host populations.

Demography and Population Viability of an Endangered Plant Species before and after Protection from Trampling - Joyce Maschinski; Robert Frye; Sue Rutman (Conservation Biology, 1997)
Land managers often suggest fencing to protect rare plant species from being trampled in heavily used recreation areas, but there are few documented examples of the efficacy of this strategy. In a 7‐year demographic study we examined the reproduction, survival, and long‐term viability of the endangered sentry milk‐vetch (Astragalus cremnophylax var. cremnophylax) before and after protection from trampling. Demographic monitoring and population viability analyses indicated that the population has fluctuated during the 7 years. Before protection the population declined: 26% of individuals died, mortality surpassed natality, and age of first reproduction was significantly older than post‐protection. Fifty‐eight percent of the population was severely damaged. Population viability analyses of pre‐protection years predicted that the population would go extinct within 100 years. Since protection, the population stabilized, grew, and declined again. Seedlings reached reproductive maturity more quickly. Recruitment increased and peaked in 1993 coincident with abundant precipitation, but again declined in 1994. The total numbers of undamaged plants surpassed the numbers of damaged plants. Models of the post‐protection population predict stability. Multiple‐linear regression analysis indicated that winter and spring precipitation were significantly correlated with lambda. Both “good” and “bad” climatic conditions occurred during the pre‐ and post‐protection periods. Because of small population size and depauperate genetic diversity, climate will continue to influence population growth. Nevertheless, models indicate that where trampling and bad climatic conditions were coupled, extinction was accelerated. Recovery of sentry milk‐vetch will depend on continued protection, augmentation, and environmental factors, although risk of extinction remains very high.

Inf luence of Within‐Plantation Heterogeneity and Surrounding Landscape Composition on Avian Communities in Hybrid Poplar Plantations - Joann M. Hanowski; Gerald J. Niemi; Donald C. Christian (Conservation Biology, 1997)
We conducted breeding bird surveys in Minnesota, Wisconsin, and South Dakota in 12 hybrid poplar plantations and surrounding landscapes from 1992 to 1994. Plantations varied in age, shape, composition of surrounding landscape, and internal vegetative heterogeneity. Numbers of breeding bird individuals and species in plantations were lower than in surrounding forest/shrub habitat, but higher than in row crops. Numbers of individuals observed within several bird groups based on migratory status and habitat preference also differed among plantations and surrounding land‐use types. Most differences were between numbers in plantations and row crops. Year‐to‐year changes in bird species composition in plantations were more likely in plantations between ages 2 and 4 years than in younger or older plantations. Correlative evidence from canonical correspondence analysis illustrated that plantation bird communities were related to habitat in surrounding landscapes, plantation age, size, latitude, and longitude. Additionally, more heterogeneous plantations had more species, individuals, and numbers of long‐distance migrants. Plantations will likely not support bird communities that are comparable to natural forests in either species composition or species diversity. A goal would be to position them in the landscape to minimize impacts on regional biodiversity. This could be accomplished by maintaining structural diversity of plantations by creating a broad range of successional stages (ages) throughout plantations within a region. Size and connectivity of existing forest fragments may be increased by plantations, but fragmentation of natural open areas should be avoided.

An African Conservation Agency's Perspective on Advocacy - Truman Young; Alexander H. Harcourt; Michael Clinchy; Charles J. Krebs (Conservation Biology, 1997)

Nesting Success of a Disturbance‐Dependent Songbird on Different Kinds of Edges - Andrew V. Suarez; Karin S. Pfennig; Scott K. Robinson (Conservation Biology, 1997)
We compared the nesting success of a disturbance‐dependent species, the Indigo Bunting ( Passerina cyanea), on different kinds of habitat edges in five sites (225 total nests) in southern Illinois from 1989 to 1993. Nest predation rates along agricultural and abrupt, permanent edges (e.g., wildlife openings, campgrounds) were nearly twice as high as rates along more gradual edges where plant succession was allowed to occur (e.g., treefalls, streamsides, gaps created by selective logging ). Levels of brood parasitism by Brown‐headed Cowbirds ( Molothrus ater) varied significantly among sites and years, but not among edge types. Clutch sizes, however, were significantly smaller at agricultural edges where nest predation rates were also high, which suggests either decreased food availability or a population dominated by younger and/or lower‐quality ( poor condition) birds. The results of this study illustrate the need to reevaluate management practices (e.g., wildlife openings) that are designed to promote populations of disturbance‐dependent wildlife.

619 Ecosystem Management Projects - Thomas R. Stanley; Joel T. Heinen; James R. Strittholt; Philip M. Fearnside; Gillian Cooper‐Driver (Conservation Biology, 1997)

Focal Species: A Multi‐Species Umbrella for Nature Conservation - Robert J. Lambeck (Conservation Biology, 1997)
To prevent the further loss of species from landscapes used for productive enterprises such as agriculture, forestry, and grazing, it is necessary to determine the composition, quantity, and configuration of landscape elements required to meet the needs of the species present. I present a multi‐species approach for defining the attributes required to meet the needs of the biota in a landscape and the management regimes that should be applied. The approach builds on the concept of umbrella species, whose requirements are believed to encapsulate the needs of other species. It identifies a suite of “focal species,” each of which is used to define different spatial and compositional attributes that must be present in a landscape and their appropriate management regimes. All species considered at risk are grouped according to the processes that threaten their persistence. These threats may include habitat loss, habitat fragmentation, weed invasion, and fire. Within each group, the species most sensitive to the threat is used to define the minimum acceptable level at which that threat can occur. For example, the area requirements of the species most limited by the availability of particular habitats will define the minimum suitable area of those habitat types; the requirements of the most dispersal‐limited species will define the attributes of connecting vegetation; species reliant on critical resources will define essential compositional attributes; and species whose populations are limited by processes such as fire, predation, or weed invasion will define the levels at which these processes must be managed. For each relevant landscape parameter, the species with the most demanding requirements for that parameter is used to define its minimum acceptable value. Because the most demanding species are selected, a landscape designed and managed to meet their needs will encompass the requirements of all other species.

In Defense of the Epidemic Disease Hypothesis - William F. Laurance; Keith R. Mcdonald; Richard Speare (Conservation Biology, 1997)

Population Viability Analysis of Spring Chinook Salmon in the South Umpqua River, Oregon - Susan Ratner; Russell Lande; Brett B. Roper (Conservation Biology, 1997)
Run sizes of spring chinook salmon in the South Umpqua River in Oregon have declined dramatically since the early part of this century. Habitat degradation is thought to be an important factor contributing to the decline of this stock, and qualitative assessment suggests the stock is at moderate risk of extinction. We use data from this and similar stocks to develop an age‐structured, density‐dependent model of the population dynamics that incorporates both demographic and environmental stochasticity. Under the assumption of no further habitat destruction, the population is predicted to have a greater than 95% probability of persistence for 200 years. However, sensitivity analysis for the density‐dependence estimated from historical run‐return data shows that substantially lower predicted viabilities are also statistically consistent with the data. A model that simulates continued habitat degradation results in almost certain extinction within 100 years.

Risk Analysis of Hunting of Seal Populations in the Baltic - Hanna Kokko; Jan Lindström; Esa Ranta (Conservation Biology, 1997)
Vulnerabilities of grey seal ( Halichoerus grypus) and ringed seal ( Phoca hispida) populations in the Baltic Sea were evaluated for potential opening of the populations for hunting. We used ecological risk analysis to assess the effects of environmental and demographic stochasticity and uncertain and partly missing population data on the modeled outcomes. The impact of different harvesting strategies on the long‐term sustainability of seal populations was analyzed with four different models with increasing complexity and population detail. It appears the simpler the population model used, the more overconfident results it gave with regard to the hunting policy to be adopted. Therefore, it proves risky in population management decisions to rely on simplistic calculations based on growth rate and estimated population size alone. This is even more so if the population estimates have a wide error margin. Due to an unknown, but presumably positive number of seal kills in the Baltic at present, the sustainable harvest is likely to be close to zero for both seal species. Our risk analysis strongly suggests refraining from Baltic seal hunting now, with their current population sizes, and in the future if the development of population numbers cannot be assessed accurately enough.

Effects of Social Structure and Prey Dynamics on Extinction Risk in Gray Wolves - John A. Vucetich; Rolf O. Peterson; Thomas A. Waite (Conservation Biology, 1997)
Extinction models based on diffusion theory generally fail to incorporate two important aspects of population biology—social structure and prey dynamics. We include these aspects in an individual‐based extinction model for small, isolated populations of the gray wolf (Canis lupus). Our model predicts mean times to extinction significantly longer than those predicted by more general (diffusion) models. According to our model, an isolated population of 50 wolves has a 95% chance of surviving just 9 years and only a 30% chance of surviving beyond 100 years. Reflecting the influence of social structure, a wolf population initially comprising 50 individuals is expected to persist only a few years longer, on average (71 years), than is a population initially comprising just a single reproductive pair (62 years). In contrast, substantially greater average prey abundance leads to dramatically longer expected persistence times. Autocorrelated prey dynamics result in a more complex distribution of extinction times than predicted by many extinction models. We contend that demographic stochasticity may pose the greatest threat to small, isolated wolf populations, although environmental stochasticity and genetic effects may compound this threat. Our work highlights the importance of considering social structure and resource dynamics in the development of population viability analyses.

Patterns of the Remnant Cichlid Fauna in Southern Lake Victoria - Ole Seehausen; Frans Witte; Egid F. Katunzi; Jan Smits; Niels Bouton (Conservation Biology, 1997)
During the years 1984–1987 Lake Victoria in East Africa experienced what is probably the largest mass extinction of contemporary vertebrates. Within a decade about 200 endemic species of haplochromine cichlids disappeared. The extinctions that occurred in the 1980s have been documented predominantly on species of offshore and sub‐littoral waters in the Mwanza Gulf of southern Lake Victoria. Although the littoral fauna of southern Lake Victoria had not been examined in detail, their diversity seemed less affected by the changes in the ecosystem. We give results of the first comprehensive inventory of the littoral cichlid fauna in southern Lake Victoria and discuss its conservation status. We also report on new developments in the sub‐littoral fauna after 1990. More than 50 littoral and 15 sub‐littoral stations were sampled between the years 1991 to 1995. Of the littoral stations, 34 were sampled for the first time. One hundred sixty three species of haplochromines were collected. Of these, 102 species were previously unknown. About two thirds of them live in rocky areas that were sampled for the first time. Littoral rocky habitats harbored the highest diversity. Since 1990, however, 13 more species disappeared from established sampling stations in littoral habitats. Fishing practices, spreading of exotic fishes, water hyacinth, and eutrophication are considered important threats to the littoral fauna. Also in the upper sub‐littoral the number of species declined further. On deeper sub‐littoral mud bottoms individual and species numbers increased again, although they are nowhere close to those found before the Nile perch (Lates niloticus) upsurge. This fauna differs from the well studied pre‐Nile perch fauna. At well‐established sampling stations, the sub‐littoral zone is dominated by previously unknown species, and some known species have performed dramatic habitat shifts.

The Sound of T. S. Eliot’s Whimper - S. Cord Stier (Conservation Biology, 1997)

Effects of Habitat Loss and Fragmentation on the Behavior and Demography of Gray‐Tailed Voles - Jerry O. Wolff; Eric M. Schauber; W. Daniel Edge (Conservation Biology, 1997)
We monitored the short term behavioral and demographic responses of gray‐tailed voles (Microtus canicaudus) to the reduction and fragmentation of their habitat. Our objectives were (1) to test whether animals perished or moved into remaining fragments after 70% of their habitat was removed; and (2) to test the null hypothesis that the social structure and demography of animals would not differ between habitats consisting of one large continuous fragment (625 m 2 ), a mosaic of 25 small fragments (each 25 m 2 ) separated by 4 m of bare ground, and control, unmanipulated habitats (1850 m 2 ). We conducted the experiment in 12, 0.2‐ha enclosures planted with alfalfa with four replicates for each of two manipulated treatments and a control. A 70% reduction in habitat did not adversely affect adult survival, reproductive rate, juvenile recruitment, or population size. However, an influx of unrelated females into habitat fragments resulted in decreased juvenile recruitment in those fragments. Voles from cleared habitat moved into the remaining habitat and did not measurably affect the resident population. Similarly, the demography of voles did not differ significantly among the large‐fragment, small‐fragment, and control enclosures. Peak density estimates based on the amount of habitat in each enclosure were 545 animals per hectare in control, 1056 in large‐fragment, and 2880 in small‐fragment enclosures. Reduced movement of animals among the small fragments was the most obvious effect of habitat fragmentation. Six percent of females and 15% of males moved among small fragments within a week compared to approximately 60% moving comparable distances in large‐fragment and control enclosures. Rates of juvenile dispersal and sexual maturation declined throughout the summer on all treatments, were associated with season and density, and were only marginally associated with habitat loss and fragmentation. We conclude that at the time of habitat removal and fragmentation, populations were small enough to accommodate a 70% reduction in habitat and still continue to increase in numbers. The social system of gray‐tailed voles was sufficiently flexible to accommodate an influx of animals to withstand densities> 1000 voles per ha. The behavioral and demographic features of gray‐tailed voles are similar to those reported for other small mammals, thus confirming the use of voles for ecological model systems in habitat fragmentation studies.

Use of Redd Counts to Detect Trends in Bull Trout ( Salvelinus conf luentus ) Populations - B. E. Rieman; D. L. Myers (Conservation Biology, 1997)

Wildlife Conservation in Taiwan - Minna J. Hsu; Govindasamy Agoramoorthy; Konjev Desender; Leon Baert; Héctor Reyes Bonilla (Conservation Biology, 1997)

Anthropogenic Correlates of Species Richness in Southeastern Ontario Wetlands - C. Scott Findlay; Jeff Houlahan (Conservation Biology, 1997)
We examined the relationship between the richness of four different wetland taxa (birds, mammals, herptiles, and plants) in 30 southeastern Ontario, Canada wetlands and two anthropogenic factors: road construction and forest removal/conversion on adjacent lands. Data were obtained from two sources: road densities and forest cover from 1:50,000 Government of Canada topographic maps and species lists and wetland areas from Ontario Ministry of Natural Resources wetland evaluation reports. Multiple regression analysis was used to model the relationships between species richness and wetland area, road density, and forest cover. Our results show a strong positive relationship between wetland area and species richness for all taxa. The species richness of all taxa except mammals was negatively correlated with the density of paved roads on lands up to 2 km from the wetland. Furthermore, both herptile and mammal species richness showed a strong positive correlation with the proportion of forest cover on lands within 2 km. These results provide evidence that at the landscape level, road construction and forest removal on adjacent lands pose significant risks to wetland biodiversity. Furthermore, they suggest that most existing wetland policies, which focus almost exclusively on activities within the wetland itself and/or a narrow buffer zone around the wetland perimeter, are unlikely to provide adequate protection for wetland biodiversity.

Pre‐Columbian Native American Use of Fire on Southern Appalachian Landscapes - Hazel R. Delcourt; Paul A. Delcourt (Conservation Biology, 1997)

Epidemic Disease and Amphibian Declines in Australia - Jean‐Marc Hero; Graeme R. Gillespie (Conservation Biology, 1997)

Conservation Implications of the Natural Loss of Lineages in Wild Mammals and Birds - Matthew E. Gompper; Peter B. Stacey; Joel Berger (Conservation Biology, 1997)
Because populations in zoological parks and nature reserves often are derived from only a few individuals, conservationists have attempted to minimize founder effects by equalizing family group sizes and increasing the reproductive contributions of all individuals. Although such programs reduce potential losses of genetic diversity, information is rarely available about the actual persistence of family groups or genetic lineages in natural populations. In the absence of such data, it can be difficult to weigh the importance of human intervention in the conservation of small populations. Separate long‐term studies of two mammals, the North American bison (Bison bison) and the white‐nosed coati (Nasua narica), and a bird, the Acorn Woodpecker (Melanerpes formicivorus), demonstrate differential extinction of genetic lineages. Irrespective of the mechanisms affecting population structure, which may range from stochastic environmental events to such behavioral phenomena as poor intrasexual competitive abilities, our results show that lineages can be lost at rapid rates from natural populations. A survey of comparable studies from the literature indicates that the loss of matrilines over the course of the study varies from 3% to 87% in wild mammals and from 30% to 80% in birds, with several small mammals losing approximately 20% of matrilines per year of study. These lineage extinctions were not an artifact of the length of the study or the generation time of the species. Such rapid losses of lineages in less than 20‐year periods in natural populations suggest that efforts to maintain maximal genetic diversity within populations may not always reflect processes that occur in the wild. Conservation biologists need to give further thought to the extent to which parity among genetic lines should be a primary goal of management of captive and small wild populations.

Cloning and Conservation of Biological Diversity: Paradox, Panacea, or Pandora’s Box? - Kamaljit S. Bawa ret; shaily Menon Leah R. Gorman (Conservation Biology, 1997)

Genetic differentiation in the New Zealand sea urchin Evechinus chloroticus (Echinodermata: Echinoidea) - P. V. Mladenov; R. M. Allibone; G. P. Wallis (New Zealand Journal of Marine and Freshwater Research, 1997)
Genetic differentiation in the New Zealand sea urchin Evechinus chloroticus (Valenciennes) was studied by examining individuals collected from six widely separated (250–2200 km apart) sites from around New Zealand for genetic variation at five polymorphic enzyme loci. Despite the large geographic separations, values of Nei's unbiased genetic distance, D (0–0.019) and standardised genetic variation among populations, F ST (0.01–0.02) were small. This indicates high levels of gene flow among populations. However, one population sampled in a fiord in south‐western New Zealand was genetically differentiated from the others, although the scale of differentiation was not large ( D = 0.011–0.019). These findings indicate: (1) that the long‐lived planktotrophic larva of E. chloroticus provides this species with considerable dispersal ability throughout its range; and (2) that this is little affected by oceanographic features peculiar to its range, such as the Subtropical Convergence or the southward flowing East Cape Current. The slight differentiation of the fiord population probably results from restricted larval dispersal into and out of the fiord. In terms of management of the E. chloroticus fishery, the results provide no evidence for discrete stocks, with the possible exception of Fiordland. It is prudent to manage the fiord populations conservatively until they are better studied.

Seasonal changes in factors controlling phytoplankton growth in Beatrix Bay, New Zealand - M. M. Gibbs; W. N. Vant (New Zealand Journal of Marine and Freshwater Research, 1997)
Phytoplankton biomass and growth rates were measured in Beatrix Bay, Marlborough Sounds, during 1994–95. In spring and summer, nitrate and chlorophyll a concentrations in the mixed layer were low (typically 3 and a m −3 , respectively), and phytoplankton growth rates were moderate (average 0.3 d −1 ). Growth rates increased several‐fold in response to the experimental addition of inorganic N (but not to inorganic phosphorus). Higher nitrate concentrations were found below the pycnocline. During autumn and winter, nitrate concentrations in the mixed layer were high (up to 60 mg m 3 ), but phytoplankton growth rates were lower than in summer (average 0.2 d −1 ), and did not respond to added nutrients. Chlorophyll a concentrations, however, were highest during the winter (typically 3–6 mg m −3 ). Even so, low light levels meant integral photosynthesis per unit chlorophyll a was low in winter. Phytoplankton growth appears to be controlled by the availability of nitrogen in summer and by light in winter.

Head capsule deformities in Chironomus zealandicus (Diptera: Chironomidae): Influence of site and substrate - Kanapathippillai Jeyasingham; Nicholas Ling (New Zealand Journal of Marine and Freshwater Research, 1997)
The natural incidence of deformities in the larval head capsules of Chironomus zealandicus was investigated at four lake sites in the central North Island, New Zealand, in summer (December 1994) and winter (June 1995). Significant differences were observed between sites and seasons. Individuals from the peat lakes Ngaroto and Hamilton (Rotoroa) had the highest incidence of deformities during summer (78 and 48%, respectively) and these declined significantly in winter (40 and 26%). No seasonal differences were observed in larvae from the two sites chosen in Lake Rotorua. Individuals close to the Hamurana Stream in Lake Rotorua showed the lowest number of malformed head capsules during summer (32%). In order to assess the influence of substrate type, larvae from two different locations were cultured through their entire life cycle in three different substrates. Results overall indicated no clear pattern of substrate effect although some structures may be more sensitive indicators of substrate physico‐chemistry than others. The incidence of deformity tended to decline with successive laboratory culture.

Seiche modes of Wellington Harbour, New Zealand - Edward R. C. Abraham (New Zealand Journal of Marine and Freshwater Research, 1997)
Seiche currents were observed in Wellington Harbour, New Zealand, with an Acoustic Doppler Current Profiler (ADCP). A 600 kHz Broad‐Band ADCP was deployed on the sea bed in Evans Bay in an upwards looking configuration for 20 days. The measured seiche periods were 159, 26, 17.3, and 8.3 min and there was evidence for seiching at periods of 15.8 and 14.7 min. These observations are in close agreement with the previous predictions of a finite‐difference numerical model. The seiching occurred during periods of wind with speeds in excess of 10 m s −1 The seiches were found to be barotropic.

Modelling the distribution of velocity in a river cross‐section - Derek G. Goring; Jeremy M. Walsh; Peter Rutschmann; Jürg Trösch (New Zealand Journal of Marine and Freshwater Research, 1997)
A method is described for modelling the distribution of velocity across a river cross‐section in a straight reach in uniform, steady flow. The method uses a finite element model based on a simplified Navier‐Stokes equation and a mixing length hypothesis. The model is applied to a representative river reach and a comparison is made with velocity gaugings in the reach. Good agreement is shown where flow conditions match the assumptions on which the model is based.

Acute ammonia toxicity for eight New Zealand indigenous freshwater species - Jody Richardson (New Zealand Journal of Marine and Freshwater Research, 1997)
The acute toxicity of un‐ionised ammonia to seven New Zealand indigenous fish and one indigenous crustacean species was established. Shrimp ( Paratya curvirostris ) was the most sensitive species, followed by banded kokopu ( Galaxias fasciatus ), common bully ( Gobiomorphus cotidianus ), common smelt ( Retropinna retropinna ), redfin bully ( G. huttoni ), inanga ( Galaxias maculatus ), and longfin and shortfin eels ( Anguilla dieffenbachii and A. australis ). The 96 h LC 50 at 15°C and pH 7.5 and pH 8.1 ranged from 0.75 to 2.35 mg NH 3 I −1 for these species. Unusually, New Zealand fish were more tolerant to ammonia than some native invertebrate species tested by a similar method. Within the limits of the life stages and species tested here, adequate protection is provided for native fish by adopting US Environmental Protection Agency ammonia criteria.

Aspects of the hydrodynamics of Beatrix Bay and Pelorus Sound, New Zealand - P. J. H. Sutton; M. G. Hadfield (New Zealand Journal of Marine and Freshwater Research, 1997)
Hydrographic and current meter measurements were performed to determine the important physical processes in Beatrix Bay, an enclosed bay in Pelorus Sound, South Island, New Zealand over a 9‐month period. The water within the bay was highly variable in temperature, salinity, and density, but strongly stratified on all occasions, with the stratification approximating a two‐layer system. The stratification was usually dominated by salinity, but on one occasion, following a period of low rainfall, the stratification was dominated by temperature. A crude estimate of the residence time for the water in Pelorus Sound is calculated from the relaxation towards oceanic salinities during the dry period. The currents measured were largely tidal, and showed evidence of a strong internal tide as a result of the quasi‐two‐layer stratification. The tidal flows were larger than those predicted by a simple model.

Catch characteristics of commercial gill‐nets in a nearshore fishery in central New Zealand - Michael J. H. Hickford; David R. Schiel; J. Brian Jones (New Zealand Journal of Marine and Freshwater Research, 1997)
Commercial gill‐nets of three mesh sizes (3.5”, 4.5”, 5.5” diagonal measure) were joined into a single net 300 m long and 5 m high, and set at three localities (New Plymouth, Palliser Bay, Bay of Plenty) in the lower North Island, New Zealand. The nets were bottom‐set in shallow (9–26 m depth) and deep (35–100 m depth) water, mostly for 16 h, to test the effects of mesh size on the species composition and sizes of fish caught. In 17 sets, 3284 fish of 55 species were caught. Across all species, larger fish were caught in deep water and at the two largest mesh sizes. The species caught and proportional composition of the catches varied both between locations and mesh sizes. Overall, there were important differences between mesh sizes, depths, and locations in the species composition and size distribution of gill‐net catches, as well as a wide range of species and sizes caught within single sets. Indications are that effective targeting of individual species at the nearshore‐pelagic interface may be confounded by bycatch.

Size‐fractionated phytoplankton standing stocks and primary production during austral winter and spring 1993 in the Subtropical Convergence region near New Zealand - J. M. Bradford‐Grieve; F. H. Chang; M. Gall; S. Pickmere; F. Richards (New Zealand Journal of Marine and Freshwater Research, 1997)
Size‐fractionated phytoplankton standing stocks and potential primary production (PPP) off the west and east coasts of South Island, New Zealand, were evaluated in austral winter and spring 1993. These are the first size‐fractionated primary production data to be reported from the southern Subtropical Convergence (STC) and in oceanic New Zealand waters. Picophytoplankton ( 30% of integrated chlorophyll a and daily PPP in most water types and seasons, except when the 20–200 μm size class dominated in west coast waters in spring and in the STC in winter and spring. In subtropical and STC waters, PPP was 30% higher than at similar latitudes in the North Atlantic Ocean. Interpretation of whether or not there was accumulation of chlorophyll a in the various water types and seasons depends on microzooplankton grazing, because mesozooplankton grazing and the proportion of chlorophyllous particulate matter sinking out of the upper water column was low. In the STC in spring, phytoplankton growth was slowing down (potential doubling times were at most 1.01 per day at 10 m and PPP per unit biomass was lower than in water masses to the north and south), probably because of decreasing concentrations of dissolved reactive silica. A sedimentation event of diatoms is postulated to have occurred in the STC soon after our spring sampling dates. The balance between algal growth and loss factors in the south‐west Pacific depends on the unique combination of physical and chemical environmental conditions experienced there. The implications of the distribution of phytoplankton biomass and primary production by size‐fraction for carbon export is discussed.

Do planktivorous fish structure the zooplankton communities in New Zealand lakes? - Erik Jeppesen; Torben Lauridsen; Stuart F. Mitchell; Carolyn W. Burns (New Zealand Journal of Marine and Freshwater Research, 1997)
We critically evaluate the prevailing view that the species composition of zooplankton communities in New Zealand lakes, and the abundance and size distribution of the zooplankton, are more commonly controlled by food and temperature than by predation. We conclude that predation may play a far more important role than was hitherto thought. This conclusion is based first on the seasonal zooplankton dynamics of several New Zealand lakes being similar to those in Danish lakes, in which fish predation has been shown to have major effects. Second, the indigenous planktivorous fish fauna in New Zealand lakes is dominated by larvae of benthic fish with a long breeding season (bullies) and other small potent zooplanktivores such as smelt and larvae of galaxiids. Patterns of diurnal vertical migration of zooplankton in several New Zealand lakes during summer are also consistent with it being a mechanism to escape from predation. Third, the dominant piscivorous fish (brown trout and rainbow trout) are only facultative piscivores and are therefore probably weaker predators on the planktivores than the more obligate piscivores in many north‐temperate lakes. Although various other explanations have been offered for the low ratio of zooplankton‐to‐phytoplankton biomass observed in New Zealand lakes, this phenomenon is equally consistent with high rates of predation. Re‐analyses of data from earlier investigations in Tomahawk Lagoon No. 2, provide evidence for a periodically high predation pressure on zooplankton during summer, which was further supported experimentally. We call for further investigation of top‐down control of zooplankton in New Zealand lakes. It is important not only for scientific understanding, but potentially also for lake management.

Mouth gape, food size, and diet of the common smelt Retropinna retropinna (Richardson) in the Waikato River system, North Island, New Zealand - Jacques A. T. Boubee; Fredrick J. Ward (New Zealand Journal of Marine and Freshwater Research, 1997)
The feeding ecology of the common smelt, Retropinna retropinna , was determined at several locations on the Waikato River system. The mean size of the dominant prey was found to increase as smelt mouth gape increased. Smelt smaller than 40 mm total length fed mostly on zooplankton. Chironomid larvae, pupae, and adults were the dominant foods of larger fish from most sites, although mysids and amphipods were the major prey in Lake Waahi and the Waikato River estuary. Algae were the dominant food in many smelt but ingestion was probably incidental. Seasonal and annual differences in dominant foods were minor. Common smelt are generalists, capable of feeding on the majority of smaller organisms present in their different environments; however, they may grow faster and achieve a larger adult size when food of optimal size and nutritive value is present.

Effects of Forest Fragmentation on Mortality and Damage of Selected Trees in Central Amazonia - Leandro V. Ferreira; William F. Laurance (Conservation Biology, 1997)

Beating Back the Brownlash (Conservation Biology, 1997)

Letters - American Zoo; Aquarium Association; Old Georgetown Road; Bethesda; Md U.S.A.; Department of Animal& Plant Sciences; University of Sheffield; Sheffield S10 Tn; United Kingdom; Institute of Zoology; Zoological Society of London; Regent's Park; et al. (Conservation Biology, 1997)

Periodic Migration and Lowland Forest Refugia in a "Sedentary" Neotropical Bird, Wetmore's Bush-Tanager. Migracion Esporadica y Refugios en Bosques de Llanuras en una Especie Sedentaria de Ave Neotropical, el Chinchinero Comun - Kevin Winker; Patricia Escalante; John H. Rappole; Mario A. Ramos; Richard J. Oehlenschlager; Dwain W. Warner (Conservation Biology, 1997)

Biological Characteristics, Habitat Associations, and Distribution of Macrofungi in Sweden. Caracteristicas Biologicas, Asociaciones de Habitat y Distribucion de Macrohongos en Suecia - Hakan Rydin; Martin Diekmann; Tomas Hallingback (Conservation Biology, 1997)

A Breeding Ground for Conservation Biologists - Francis E. Putz (Conservation Biology, 1997)

Natural History: Hobby or Science? - Jesus Antonio Rivas (Conservation Biology, 1997)

Ecological Impact of Introduced Crayfish on Benthic Fishes in a British Lowland River. Impacto Ecologico de un Langostino de Rio Introducido en Poblaciones de Peces Bentonicos de un Rio de las Tierras Bajas Britanicas - Rui-Zhang Guan; Peter Roy Wiles (Conservation Biology, 1997)

Juvenile Survival in a Population of Neotropical Migrant Birds. Supervivencia de Juveniles en una Poblacion de Aves Migratorias Neotropicales - Angela D. Anders; Donald C. Dearborn; John Faaborg; Frank R. Thompson Iii (Conservation Biology, 1997)

Aggression by Non-Native Crayfish Deters Breeding in California Newts - Seth C. Gamradt; Lee B. Kats; Christopher B. Anzalone (Conservation Biology, 1997)

Invertebrates and Boreal Forest Management. Invertebrados y Manejo de Bosques Boreales - Jari Niemela (Conservation Biology, 1997)

Orangutan Rehabilitation in Tanjung Puting National Park, Indonesia - Carey P. Yeager (Conservation Biology, 1997)

The Use of Corridors by Mammals in Fragmented Australian Eucalypt Forests. Uso de Corredores por Mamiferos en Bosques de Eucalipto en Australia - Sharon J. Downes; Kathrine A. Handasyde; Mark A. Elgar (Conservation Biology, 1997)

Spatial Scale and Determination of Species Status of the Green Frog. Escala Espacial y Determinacion del Estatus de la Especie de Rana Verde - Stephen J. Hecnar; Robert T. M'Closkey (Conservation Biology, 1997)

Critique of the Evolutionarily Significant Unit as a Definition for "Distinct Population Segments" under the U.S. Endangered Species Act. Critica de la Unidad Evolutivamente Significativa como una Definicion de los "Segmentos Poblacionales Notables" en el Acta de Especies en Peligro de E.U.A. - David S. Pennock; Walter W. Dimmick (Conservation Biology, 1997)

A Comparison of Corridors and Intrinsic Connectivity to Promote Dispersal in Transient Successional Landscapes. Comparacion de Corredores y Conectividad Intrinseca para Promover la Dispersion en Paisajes Sucesionales Transitorios - Harry M. Tiebout Iii; Roger A. Anderson (Conservation Biology, 1997)

Lessons in Ecosystem Management from Management of Threatened and Pest Loranthaceous Mistletoes in New Zealand and Australia. Lecciones de Manejo de Ecosistemas Manejo de Muerdagos Lorantaceos Amenazados y Plagas en Nueva Zelanda y Australia - David A. Norton; Nick Reid (Conservation Biology, 1997)