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"Evans, Brian"
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Environmental filtering of avian communities along a rural‐to‐urban gradient in Greater Washington, D.C., USA
The composition of avian communities in human‐dominated habitats is thought to be determined by the interaction between species‐specific traits and environmental characteristics. Traits such as dietary habits and habitat specialization influence the vulnerability of species to land use change. As species are excluded from anthropogenic environments, local species pools are differentially sorted from the regional species pool. This sorting process, environmental filtering, is characterized by a decline in the functional diversity of local biotic communities and may result in a loss of regional biodiversity as landscapes are urbanized. Environmental filtering due to urbanization is hypothesized due to an ecosystem stress gradient, which describes a decrease in species richness or abundance with increasing urban intensity. Conflicting patterns of species richness and species abundances have limited our ability to determine whether urban environments filter avian communities. To evaluate the hypothesis that environmental filtering is occurring, we analyzed avian point count data collected along a rural‐to‐urban gradient in metropolitan Washington, D.C. We examined predictions that species richness, functional diversity, and the total and relative abundances of some life history guilds exhibit the pattern expected under the ecosystem stress‐gradient hypothesis. Species richness and functional diversity declined monotonically with increasing impervious surface. Life history guilds, representing species’ diet, foraging, nest, and migration habits, exhibited differential rates of decline across the rural‐to‐urban gradient, resulting in marked shifts in the composition of communities. Our results support the hypothesis that urbanization filters bird communities as a function of avian traits and provide further evidence of trait‐level responses to urban environments.
Journal Article
An anionic, endosome-escaping polymer to potentiate intracellular delivery of cationic peptides, biomacromolecules, and nanoparticles
Peptides and biologics provide unique opportunities to modulate intracellular targets not druggable by conventional small molecules. Most peptides and biologics are fused with cationic uptake moieties or formulated into nanoparticles to facilitate delivery, but these systems typically lack potency due to low uptake and/or entrapment and degradation in endolysosomal compartments. Because most delivery reagents comprise cationic lipids or polymers, there is a lack of reagents specifically optimized to deliver cationic cargo. Herein, we demonstrate the utility of the cytocompatible polymer poly(propylacrylic acid) (PPAA) to potentiate intracellular delivery of cationic biomacromolecules and nano-formulations. This approach demonstrates superior efficacy over all marketed peptide delivery reagents and enhances delivery of nucleic acids and gene editing ribonucleoproteins (RNPs) formulated with both commercially-available and our own custom-synthesized cationic polymer delivery reagents. These results demonstrate the broad potential of PPAA to serve as a platform reagent for the intracellular delivery of cationic cargo.
Most reagents designed to deliver cargo into cells are cationic and so cannot deliver cationic cargo. Here the authors show that pretreating cells with the anionic polymer poly(propylacrylic acid) facilitates the uptake and endosomal escape of a wide variety of cationic cargo in numerous cell types.
Journal Article
A Monoclonal Antibody for Malaria Prevention
Malaria remains a cause of substantial global morbidity and mortality. In this report, an engineered monoclonal antibody showed protection against malaria infection in a controlled human infection model.
Journal Article
The prevalence and impact of transient species in ecological communities
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 on over 19,000 community time series spanning an array of ecosystems, taxonomic groups, and spatial scales. We found that transient species are a general feature of communities regardless of taxa or ecosystem. The proportion of these species decreases with increasing spatial scale leading to a need to control for scale in comparative work. Removing transient species from analyses influences the form of a suite of commonly studied ecological patterns including species–abundance distributions, species–energy relationships, species–area relationships, and temporal turnover. Careful consideration should be given to whether transient species are included in analyses depending on the theoretical and practical relevance of these species for the question being studied.
Journal Article
Characterizing avian survival along a rural-to-urban land use gradient
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 survivorship in suburban and urban habitats, whereas bottom-up processes, such as increased resource availability, predict peak survival in suburban habitats. In this study, we use mark-recapture data of seven focal species encountered between 2000 and 2012 to test hypotheses about the processes that regulate avian survival along an urbanization gradient in greater Washington, D.C., USA. American Robin, Gray Catbird, Northern Cardinal, and Song Sparrow exhibited peak survival at intermediate and upper portions of the rural-to-urban gradient; this pattern supports the hypothesis that bottom-up processes (e.g., resource availability) can drive patterns of avian survival in some species. In contrast, Carolina Chickadee showed no response and Carolina and House Wren showed a slightly negative response to urban land cover. These contrasting results underscore the need for comparative studies documenting the mechanisms that drive demography and how those factors differentially affect urban adapted and urban avoiding species.
Journal Article