Joshuah S. Perkin

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Effects of fragmentation on the ecology of organisms occupying dendritic ecological networks (DENs) have recently been described through both conceptual and mathematical models, but few hypotheses have been tested in complex, real-world ecosystems. Stream fishes provide a model system for assessing effects of fragmentation on the structure of communities(More)
Riverine flow regimes are naturally dynamic, but become increasingly homogenized following anthropogenic flow alteration. Loss of dynamism disrupts naturally occurring structuring mechanisms within the associated biotic communities, at times causing shifts in composition. Here we considered how stream fish assemblages in two Central Texas rivers changed(More)
Human environmental change influences freshwaters as well as the regulating, provisioning, and cultural services that ecosystems provide worldwide. Here, we assess the global human impact on the potential value of six freshwater ecosystem services (ES) and estimate the proportion of each used globally (the mean value across all countries is in parentheses):(More)
—The Guadalupe bass Micropterus treculii is endemic to Texas and is threatened by introgression with introduced smallmouth bass M. dolomieu as well as habitat degradation. This study described and quantified the movements and habitat associations of Guadalupe bass to assess the factors that may influence current populations. Radio-tagged adult Guadalupe(More)
—Anthropogenic alterations to lotic systems are often implicated in global declines among stream-dwelling fishes. A primary step toward mediating fish declines is improving our understanding of species–environment relationships; unfortunately, such information is limited. The goal of this study was to assess relationships between fish communities and(More)
Burrhead Chub Macrhybopsis marconis is a species of special concern endemic to subtropical streams in south Texas. We documented life history attributes and historical patterns in abundance and distribution to aid in understanding range-wide declines of the species among the Colorado and Guadalupe-San Antonio River systems. Life history results suggest(More)
We used comparative landscape genetics to examine the relative roles of historical events, intrinsic traits and landscape factors in determining the distribution of genetic diversity of river fishes across the North American Great Plains. Spatial patterns of diversity were overlaid on a patch-based graphical model and then compared within and among three(More)
Habitat fragmentation and loss threaten global biodiversity, but organism responses to changing habitat availability are mediated by structural properties of their habitats. In particular, organisms inhabiting dendritic landscapes with hierarchically arranged branches of habitat tend to have limited access to some patches even in the absence of(More)
The Clean Water Act of 1972 is credited with improving water quality across the USA, although few long-term studies tracking hydrologic, chemical, and biological responses to cleanup efforts exist. The Trinity River of Texas was plagued by poor water quality for more than a century before passage of legislation to reduce point source pollution from the(More)
Groundwater pumping for agriculture is a major driver causing declines of global freshwater ecosystems, yet the ecological consequences for stream fish assemblages are rarely quantified. We combined retrospective (1950-2010) and prospective (2011-2060) modeling approaches within a multiscale framework to predict change in Great Plains stream fish(More)