Dissertation Research: Phylogeography of Salamanders of the Plethodon Jordani Complex in the Southern Appalachian Mountains

Washington University, Saint Louis MO

Investigators

Abstract

Project Description The Plethodon jordani complex is an assemblage of seven high-elevation mountain species that show little morphological differentiation, but contain high levels of genetic differentiation according to surveys of protein variation. Cycles of temperature change during the most recent ice ages are predicted to have caused repeated episodes of population isolation and contact as salamanders tracked their favorable environments. These contrasting episodes may have caused genetic ivergence when isolated and genetic mixing while in contact. In many cases it is unclear how the interplay of these forces has affected species formation in this species complex. Objectives of this research are to utilize mitochondrial DNA sequences in tandem with the existing protein variation data to test hypotheses of genetic differentiation and hybrid formation among fragmented populations in the P. jordani complex through phylogenetic analyses. Project Significance Few phylogeographic studies have sufficient sampling to detect on a fine geographic scale the patterns of genetic fragmentation and secondary contact among natural populations. This study seeks to provide a detailed and fine-scale phylogeographic test of species hypotheses that were generated from protein variation. The relatively limited distribution of the Plethodon jordani complex allows extensive sampling across its distribution and, therefore, near complete characterization of genetic diversity for a mitochondrial gene. The large sample sizes and mitochondrial DNA sequences allow us to distinguish ongoing dynamic gene exchange among populations versus historically discontinuous patterns of gene exchange. Furthermore, the existence of extensive surveys of protein variation provides an ideal situation for examining combined data sources for quantifying evolutionary divergence among populations and species formation.