G. K. Roderick results 20
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Interpretable deep learning reveals spatiotemporal MRI features of brain aging that align with neurodegenerationNARA Subscribed
Cortical thinning and atrophy are hallmarks of brain aging that have been characterized using magnetic resonance imaging (MRI). Brain aging involves many neuroanatomic features whose effects on brain structure remain unexplored. To address this challenge, we trained interpretable deep neural networks (DNNs) to estimate brain age (BA) from T 1 -weighted ( T 1 w) MRI. By identifying MRI features unapparent to humans, DNNs can fi...
Alzheimer’s disease (AD) disproportionately affects women and carriers of the apolipoprotein E ε4 allele (APOE4), yet little is known about how sex and APOE interact to influence white matter (WM) integrity during disease progression. We integrated diffusion MRI and matched blood transcriptomic data to investigate these interactions and their underlying biological mechanisms. WM microstructure was quantified using diffusion te...
Predicting the progression of MCI and Alzheimer’s disease on structural brain integrity and other features with machine learningNARA Subscribed
Machine learning (ML) on structural MRI data shows high potential for classifying Alzheimer’s disease (AD) progression, but the specific contribution of brain regions, demographics, and proteinopathy remains unclear. Using Alzheimer’s Disease Neuroimaging Initiative (ADNI) data, we applied an extreme gradient-boosting algorithm and SHAP (SHapley Additive exPlanations) values to classify cognitively normal (CN) older adults, th...
Dominance and rarity in tree communities across the globe: Patterns, predictors and threatsNARA Subscribed
Aim Ecological and anthropogenic factors shift the abundances of dominant and rare tree species within local forest communities, thus affecting species composition and ecosystem functioning. To inform forest and conservation management it is important to understand the drivers of dominance and rarity in local tree communities. We answer the following research questions: (1) What are the patterns of dominance and rarity in tree...
Geography and ecology shape the phylogenetic composition of Amazonian tree communitiesNARA Subscribed
Aim Amazonia hosts more tree species from numerous evolutionary lineages, both young and ancient, than any other biogeographic region. Previous studies have shown that tree lineages colonized multiple edaphic environments and dispersed widely across Amazonia, leading to a hypothesis, which we test, that lineages should not be strongly associated with either geographic regions or edaphic forest types. Location Amazonia. Taxon A...
Current understanding of ecological and evolutionary processes underlying island biodiversity is heavily shaped by empirical data from plants and birds, although arthropods comprise the overwhelming majority of known animal species, and as such can provide key insights into processes governing biodiversity. Novel high throughput sequencing (HTS) approaches are now emerging as powerful tools to overcome limitations in the avail...
Richness and resilience in the Pacific: DNA metabarcoding enables parallelized evaluation of biogeographic patternsNARA Subscribed
Islands make up a large proportion of Earth's biodiversity, yet are also some of the most sensitive systems to environmental perturbation. Biogeographic theory predicts that geologic age, area, and isolation typically drive islands' diversity patterns, and thus potentially impact non‐native spread and community homogenization across island systems. One limitation in testing such predictions has been the difficulty of performin...
Aim Large tropical trees form the interface between ground and airborne observations, offering a unique opportunity to capture forest properties remotely and to investigate their variations on broad scales. However, despite rapid development of metrics to characterize the forest canopy from remotely sensed data, a gap remains between aerial and field inventories. To close this gap, we propose a new pan‐tropical model to predic...
Aim Remote islands are known for providing spectacular examples of adaptive radiation, with ecological divergence across a lineage giving rise to multiple species, each specialized for a particular niche. These isolated environments also provide some of the best examples of recent colonization, often human‐mediated, with a single generalist taxon distributed over vast regions. Highlighted by this dichotomy is a tendency of tax...
Aim We examine spatial and temporal patterns of diversification among flightless weevils in the genus Rhyncogonus (Curculionidae: Entiminae), with respect to their passive mode of dispersal by rafting or upon birds and the geological context of Pacific island archipelagos. Location Archipelagos and islands of the Pacific Ocean, especially the South Pacific and Hawaii. Methods Nuclear and mitochondrial DNA sequence data were us...
Aim Understanding how ecological and evolutionary processes together determine patterns of biodiversity remains a central aim in biology. Guided by ecological theory, we use data from multiple arthropod lineages across the Hawaiian archipelago to explore the interplay between ecological (population dynamics, dispersal, trophic interactions) and evolutionary (genetic structuring, adaptation, speciation, extinction) processes. O...
H alomonas sulfidaeris ‐dominated microbial community inhabits a 1.8 km‐deep subsurface C ambrian S andstone reservoirNARA Subscribed
Summary A low‐diversity microbial community, dominated by the γ ‐proteobacterium H alomonas sulfidaeris , was detected in samples of warm saline formation porewater collected from the C ambrian Mt. S imon S andstone in the I llinois B asin of the N orth A merican M idcontinent (1.8 km/5872 ft burial depth, 50° C , pH 8, 181 bars pressure). These highly porous and permeable quartz arenite sandstones are directly analogous to re...
Biodiversity dynamics in isolated island communities: interaction between natural and human‐mediated processesNARA Subscribed
The flora and fauna of oceanic islands have inspired research since the early scientific explorations. Islands can be considered ‘nature's test tubes’— simple systems with multiple replicates. Our research has used the simplicity of island systems to understand ecological community dynamics and to compare the properties of island communities with those in more complex mainland systems. Here, we present three topics: (i) curren...
Volcanic activity on the island of Hawaii results in a cyclical pattern of habitat destruction and fragmentation by lava, followed by habitat regeneration on newly formed substrates. While this pattern has been hypothesized to promote the diversification of Hawaiian lineages, there have been few attempts to link geological processes to measurable changes in population structure. We investigated the genetic structure of three s...
Growth and nutritional trials on transgenic Nile tilapia containing an exogenous fish growth hormone geneNARA Subscribed
In a long‐term growth trial, transgenic tilapia Oreochromis niloticus L. showed a 2·5‐fold increase in growth compared with non‐transgenic siblings. At 7 months, mean mass of transgenic tilapia was 653 g compared with 260 g for non‐transgenic siblings. A significant increase ( P >0·01) in head: total length ratio, viscera‐somatic index and hepato‐somatic index was observed in transgenic fish. Female gonado‐somatic index ( I G)...
Invasion genetics of the Mediterranean fruit fly: variation in multiple nuclear intronsNARA Subscribed
Biological invasions generally start from low initial population sizes, leading to reduced genetic variation in nuclear and especially mitochondrial DNA. Consequently, genetic approaches for the study of invasion history and population structure are difficult. An extreme example is the Mediterranean fruit fly, Ceratitis capitata (Medfly), for which successive invasions during this century have resulted in a loss of 60% of ance...
The Hawaiian archipelago is arguably the world’s finest natural laboratory for the study of evolution and patterns of speciation. Arthropods comprise over 75% of the endemic biota of the Hawaiian Islands and a large proportion belongs to species radiations. We classify patterns of speciation within Hawaiian arthropod lineages into three categories: (i) single representatives of a lineage throughout the islands; (ii) species ra...
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