Notes from the Underground: Linking Microhabitat and Species Distributions of Plethodontid Salamanders

Farallo, Vincent

ABSTRACT: Environmental characteristics play a pivotal role in delineating species distributions and, in turn, influence species richness, diversity, and interspecific interactions. However, species exist at various spatial and temporal scales. Therefore, the scale at which environmental data is collected will influence the interpretations of how it impacts organisms. Most species primarily exist at a small spatial scale making broad-scale climate and habitat data often less biologically relevant to these organisms. Instead microhabitat and microclimate variables are often what species will directly experience, which makes the connection between macro- and micro-scale data important for answering evolutionary and ecological questions. This dissertation quantifies microhabitat and microclimate use of plethodontid salamanders across a broad geographic area including latitudinal and elevational gradients. First, I review the importance of micro-scale environmental data and how can bolster studies in evolutionary ecology. Next, I focus on species ability to choose specific microhabitat and microclimates including direct comparisons to habitat and climates that is available to captured salamanders, but remains unused. I found that salamanders were able to choose specific environmental conditions. Furthermore, species used different microhabitat and microclimates, including closely related species. To further refine our knowledge of microhabitat and microclimate use, I include a study monitoring thermal and hydric properties of various microhabitats in the Great Smoky Mountains National Park along an elevational gradient. I found that they chose cooler and wetter microhabitats and that they chose microhabitats that maintain their hydric state even between high and low elevation sites, indicating that through behavioral compensation they may be able to extend their ranges beyond what broad-scale climate data predict. Finally, I tested for phylogenetic signal of these small-scale variables and found as whole there is no indication of phylogenetic signal. However, two individual variables relative humidity and soil temperature, have significant phylogenetic signal which appears driven by differences in the Plethodon cinereus and Plethodon glutinosus species groups. Together, these results provide a substantial contribution to our knowledge of the evolutionary ecology of plethodontid salamanders, and highlight the importance of incorporating small-scale environmental data, especially when assessing the impacts of climate change.