Effect of Urbanization on Abundance of Jollyville Plateau Salamanders (Eurycea tonkawae)


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Urbanization causes havoc to native ecosystems, resulting in population declines or extirpation of sensitive taxa. This can be devastating to narrow-range endemics whose distributions overlap or are enveloped by urban development. Jollyville Plateau Salamanders (Eurycea tonkawae) are aquatic neotenes restricted to karst-associated waters in a small, highly urbanized area of central Texas. Eurycea tonkawae was recently listed as threatened under the U.S. Endangered Species Act due to threats from urbanization, although the published literature on their population status is limited to a single, short-term study. Here, we attempt to remedy this dearth of knowledge by summarizing population survey data from sites that span the breadth of E. tonkawae’s range. We analyzed count data using Bayesian inference and generalized linear models, first to determine trends in abundance at eight sites from 1996–2011. Secondly, we examined differences in salamander density at these and an additional nine sites (n = 17) among urbanized and nonurbanized catchments from 2009–2012. Study sites occurred in catchments that ranged from undeveloped to completely built-out, from no-change in development to > 20% increases in development. Accounting for climatic variation, we found that counts of E. tonkawae declined in areas that had the largest increases in residential development (a metric of urbanization) over a 15-y period. Additionally, densities of E. tonkawae were negatively correlated with residential development across their range. We discuss several possible mechanisms responsible for declines of E. tonkawae and highlight likely causes and potential areas of future research to aid in conservation efforts for this and other central Texas Eurycea salamanders.


Edwards Aquifer, Endangered Species, Habitat Loss, Land-Use Change, Plethodontidae, Population Ecology

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Herpetological Conservation and Biology, Vol. 9, no. 1 (2014-06-13).