RISSLER, LJ: Ecology and Phylogenetics of Salamanders Across the Eastern Continental Divide

I combined ecological experiments and phylogenetic comparisons to understand how species interactions and ecology impact patterns of species distributions and genetic variance across the Eastern Continental Divide (ECD). Tributaries separated by the ECD are completely isolated via aquatic routes that either flow into the Atlantic Ocean or Gulf of Mexico. In addition, salamander assemblages vary in composition across the ECD. Natural distribution data and ecological experiments are consistent with the interpretation that species interactions influence habitat choice and the degree of terrestriality for D. monticolaand D. fuscus. In addition, D. monticolafrom populations in the New River drainage occupied more terrestrial substrates even when D. quadramaculatuswas absent. Ecological data predict that species will display differential phylogenetic patterns that reflect a graded variation in terrestriality and vagility across the ECD. However, phylogenetic analyses of the 12S rRNA and COXI genes show no pattern consistent with the prediction that ecology impacts the spatial scale of evolution. In particular, analyses of molecular variance (AMOVA) and estimates of Tajima�s D and Fu and Li statistics suggest that D. monticolahas experienced a rapid population expansion following a bottleneck in southern Alabama with subsequent northward spread. The current phylogeographic structure in the genus Desmognathusmore likely reflects patterns of historic population isolation and expansion rather than current gene flow related to vagility.