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Seminar: Dr. Edward Burress – High Elevation is an Ecological Dead End for Appalachian Salamanders
September 22 @ 3:00 pm - 4:00 pm
The southern Appalachian Mountains are a global biodiversity hotspot for salamanders. Mountains may promote high species richness by acting as evolutionary catalysts and/or refugia. How mountains influence other dimensions of diversity – ecological and phenotypic – is uncertain. Here, we assess how abiotic factors that contribute to microhabitat availability vary with elevation gradient throughout the Appalachian Mountains, surrounding foothills, and lowlands. We compare this to elevational patterns in microhabitat use, phenotype, and macroevolutionary features (adaptive peaks), in a group encompassing 89 species of lungless salamander (Plethodontidae). We find that there are broad abiotic controls on microhabitat availability along the elevational gradient. As elevation increases, the spatial distribution of cave-forming rock-types decreases (determined by large-scale geologic process), surface water availability also decreases (a function of climate and river network topology) as does soil depth (a function of geomorphic processes such as weathering). The presence of salamander microhabitat specialists is influenced by these abiotic factors, leading to a decline in microhabitat specialists, phenotypic disparity, and the number of evolutionary optima at higher elevations. While there is a multitude of microhabitat specialists at low and intermediate elevations, terrestrial species dominate salamander assemblages at high elevation. Eco-evolutionary processes operating within an abiotic framework of non-random spatial patterns in the availability of habitat leads to an ecological dead end for salamanders at high elevation.