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School of Environment and Natural Resources


TWEL Meaghan Gade Dissertation

Spatial variation in the abundance, demography, and physiology of the montane endemic salamander, Plethodon shermani, and the consequences of climate change

Meaghan Regina Gade, PhD

Advisor: William E. Peterman, PhD


As climate change marches on, it is imperative to understand how species respond via distribution, abundance, physiology, and behavior to their environment present-day in order to inform possible responses in the future. Populations of species exist across heterogeneous environments that may differentially influence particular responses. The scale at which these responses are assessed must be considered because patterns can emerge at a local scale that may not be detectable at broader scales. Yet, only assessing local-scale patterns and responses neglects the broader landscape patterns that ultimately shape fine-scales. Montane biodiversity experience extreme abiotic variation over small spatial scales.To increase our understanding of how these gradients influence wildlife across scales, my research examines the patterns of distribution, abundance, demographic life-history traits, behavior, and physiology in the red-legged salamander, Plethodon shermani, across multiple abiotic gradients in the Southern Appalachian Mountains. The primary objectives of my research are to (1) understand the effects of spatial patterns on ecological responses of P. shermani and (2) use that knowledge to predict how responses will change in the future.

Terrestrial Plethodon salamanders lack lungs and depend on cool and moist microhabitat to facilitate gas exchange across their skin surface. As such, salamanders are restricted to specific habitats. We know that salamander abundance increases with elevation due to the cool and moist regional climate at high elevations. However, my research investigates the role of both elevation and stream distance gradients as broad and fine-scale abiotic gradients, respectively, that salamanders may be responding. Although low elevations are regionally warm and dry, microhabitats near streams are buffered and tend to be cooler and wetter. I found that salamander distribution and abundance track these landscape patterns such that at low elevations, animals are distributed in their highest abundance near stream sides but become less dependent on stream-side habitat at high elevations due to the regionally cool and moist habitat. Salamander life history also varies across these gradients; survival decreases with elevation but reproductive rates and growth increase with elevation. Both survival and reproduction decrease with stream distance at low elevations, but growth and movement increase with stream distance. I also found that a metric for stress, dermal Corticosterone, (dCORT) was lowest in animals at low elevations and stream distance had no effect. Salamander dCORT additively increased in response to experimental conditions reflective of future climate change. I also found that the surface activity probability of salamanders will likely increase in the future in response to rising temperatures. Using a highly integrative approach, my research collectively shows that salamanders have multi-faceted responses to spatial variation of landscapes and will be impacted by future climate change.