Allen Hurlbert results 27
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The Multifaceted Effects of Anthropogenic and Climatic Factors on Ecological NetworksNARA Subscribed
Aim Biotic interactions, such as pollination, seed dispersal, and parasitism, are key for biodiversity and ecosystem function. Ecological networks quantify the structure of biotic interactions, providing a framework to evaluate their spatial dynamics under global change. While climate and human influence are important predictors of network structure, we hypothesize that such effects depend on the interaction type and the organ...
Species Richness Gradients Vary Across Phylogenetic ScalesNARA Subscribed
Aim To determine how species richness gradients—commonly considered universal—vary across the phylogenetic hierarchy of birds and mammals, and to uncover how clade age and size predetermine the gradients. Location Global. Time Period Last 120 million years. Taxa Studied Birds and mammals (~15,000 species). Methods We used large‐scale phylogenies of birds and mammals and captured the species richness gradient for each of their...
Motivation Here, we make available a second version of the BioTIME database, which compiles records of abundance estimates for species in sample events of ecological assemblages through time. The updated version expands version 1.0 of the database by doubling the number of studies and includes substantial additional curation to the taxonomic accuracy of the records, as well as the metadata. Moreover, we now provide an R packag...
More individuals or specialized niches? Distinguishing support for hypotheses explaining positive species–energy relationshipsNARA Subscribed
Aim Positive productivity–richness relationships have been observed across taxa and ecosystems. We assessed support for two hypotheses explaining these relationships, the More Individuals Hypothesis (MIH) and the Niche Specialization Hypothesis (NSH) in two complementary datasets of avian communities in North America, the Breeding Bird Survey (BBS), which has been widely used to study productivity–richness relationships, and t...
Anthropogenic change has altered the composition and function of ecological communities across the globe. As a result, there is a need for studies examining observed community compositional change and determining whether and how anthropogenic change drivers may be influencing that turnover. In particular, it is also important to determine to what extent community turnover is idiosyncratic or if turnover can be explained by pre...
The relative importance of biotic and abiotic determinants of temporal occupancy for avian species in North AmericaNARA Subscribed
Aim We examined the relative importance of competitor abundance and environmental variables in determining the species distributions of 175 bird species across North America. Unlike previous studies, which tend to model distributions in terms of presence and absence, we take advantage of a geographically extensive dataset of community time series to model the temporal occupancy of species at sites throughout their expected ran...
Transient species occur infrequently in a community over time and do not maintain viable local populations. Because transient species interact differently than non‐transients with their biotic and abiotic environment, it is important to characterize the prevalence of these species and how they impact our understanding of ecological systems. We quantified the prevalence and impact of transient species in communities using data...
Motivation The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community‐led open‐source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal...
Environmental optimality, not heterogeneity, drives regional and local species richness in lichen epiphytesNARA Subscribed
Aim We evaluate the scale dependence of species richness–environment relationships with a continent‐wide analysis of lichen epiphyte communities. Specifically, our goals are to assess: (1) the dependence of local richness on regional processes, (2) whether species richness is primarily influenced by heterogeneity in environmental conditions or the central tendency of those conditions, and (3) whether the relative influence of...
Many avian species persist in human‐dominated landscapes; however, little is known about the demographic consequences of urbanization in these populations. Given that urban habitats introduce novel benefits (e.g., anthropogenic resources) and pressures (e.g., mortality risks), conflicting mechanisms have been hypothesized to drive the dynamics of urban bird populations. Top‐down processes such as predation predict reduced surv...
The role of urban and agricultural areas during avian migration: an assessment of within‐year temporal turnoverNARA Subscribed
Aim Migration is often identified as the most vulnerable period in the annual cycle for birds, and land‐use change is likely to have altered how avian populations are regulated during migration events. However, the consequences of land‐use change for avian diversity are typically assessed based on annual surveys of breeding communities with little consideration given to migration or other phases of the annual cycle. Location F...
Energetic constraints are fundamental to ecology and evolution, and empirical relationships between species richness and estimates of available energy (i.e. resources) have led some to suggest that richness is energetically constrained. However, the mechanism linking energy with richness is rarely specified and predictions of secondary patterns consistent with energy‐constrained richness are lacking. Here, we lay out the neces...
Stochastic and deterministic drivers of spatial and temporal turnover in breeding bird communitiesNARA Subscribed
Aim A long‐standing challenge in ecology is to identify the suite of factors that lead to turnover in species composition in both space and time. These factors might be stochastic (e.g. sampling and priority effects) or deterministic (e.g. competition and environmental filtering). While numerous studies have examined the relationship between turnover and individual drivers of interest (e.g. primary productivity, habitat hetero...
Broad‐scale ecological implications of ectothermy and endothermy in changing environmentsNARA Subscribed
Aim Physiology is emerging as a basis for understanding the distribution and diversity of organisms, and ultimately for predicting their responses to climate change. Here we review how the difference in physiology of terrestrial vertebrate ectotherms (amphibians and reptiles) and endotherms (birds and mammals) is expected to influence broad‐scale ecological patterns. Location Global terrestrial ecosystems. Methods We use data...
Temporal turnover in the composition of tropical tree communities: functional determinism and phylogenetic stochasticityNARA Subscribed
The degree to which turnover in biological communities is structured by deterministic or stochastic factors and the identities of influential deterministic factors are fundamental, yet unresolved, questions in ecology. Answers to these questions are particularly important for projecting the fate of forests with diverse disturbance histories worldwide. To uncover the processes governing turnover we use species‐level molecular p...
Patterns of species turnover may reflect the processes driving community dynamics across scales. While the majority of studies on species turnover have examined pairwise comparison metrics (e.g., the average Jaccard dissimilarity), it has been proposed that the species–area relationship (SAR) also offers insight into patterns of species turnover because these two patterns may be analytically linked. However, these previous lin...
Aim Body size often plays a significant role in community assembly through its impacts on the life history and ecological attributes of species. Insight into the importance of size in structuring communities can be gained by examining the distribution of sizes of individuals [i.e. the individual size distribution (ISD) or size spectrum] in a community. ISDs have been studied extensively in aquatic and tree communities, but hav...
Taking species abundance distributions beyond individualsNARA Subscribed
The species abundance distribution (SAD) is one of the few universal patterns in ecology. Research on this fundamental distribution has primarily focused on the study of numerical counts, irrespective of the traits of individuals. Here we show that considering a set of Generalized Species Abundance Distributions (GSADs) encompassing several abundance measures, such as numerical abundance, biomass and resource use, can provide...
Island biogeography of Caribbean coral reef fishNARA Subscribed
Aim The goal of our study was to test fundamental predictions of biogeographical theories in tropical reef fish assemblages, in particular relationships between fish species richness and island area, isolation and oceanographic variables (temperature and productivity) in the insular Caribbean. These analyses complement an analogous and more voluminous body of work from the tropical Indo‐Pacific. The Caribbean is more limited i...
Aim The degree to which a species is predictably encountered within its range varies tremendously across species. Understanding why some species occur less frequently within their range than others has important consequences for conservation and for analyses of ecological patterns based on range maps. We examined whether patterns in geographical range occupancy can be explained by species‐level traits. Location North America....
Species abundance distributions: moving beyond single prediction theories to integration within an ecological frameworkNARA Subscribed
Species abundance distributions (SADs) follow one of ecology’s oldest and most universal laws – every community shows a hollow curve or hyperbolic shape on a histogram with many rare species and just a few common species. Here, we review theoretical, empirical and statistical developments in the study of SADs. Several key points emerge. (i) Literally dozens of models have been proposed to explain the hollow curve. Unfortunatel...
Challenges in the application of geometric constraint modelsNARA Subscribed
Discerning the processes influencing geographical patterns of species richness remains one of the central goals of modern ecology. Traditional approaches to exploring these patterns have focused on environmental and ecological correlates of observed species richness. Recently, some have suggested these approaches suffer from the lack of an appropriate null model that accounts for species ranges being constrained to occur withi...
Evolution and the latitudinal diversity gradient: speciation, extinction and biogeographyNARA Subscribed
A latitudinal gradient in biodiversity has existed since before the time of the dinosaurs, yet how and why this gradient arose remains unresolved. Here we review two major hypotheses for the origin of the latitudinal diversity gradient. The time and area hypothesis holds that tropical climates are older and historically larger, allowing more opportunity for diversification. This hypothesis is supported by observations that tem...
Resource availability is an important constraint on community structure. Some authors have suggested it conceptually links two of the most basic patterns in ecology, the species–area relationship and the latitudinal gradient in species richness. I present the first experimental test of this conjecture, by manipulating both the area and resource concentration of artificial larval drosophilid fly habitats and then allowing colon...