PRINCIPLES OF PHYLOGEOGRAPHY AS ILLUSTRATED BY FRESHWATER AND TERRESTRIAL TURTLES IN THE SOUTHEASTERN UNITED STATES

Geographic patterns in mtDNA variation are compiled for 22 species of freshwater and terrestrial turtles in the southeastern United States, and the results are employed to evaluate phylogeographic hypotheses and principles of genealogical concordance derived previously from similar analyses of other vertebrates in the region. The comparative molecular findings are interpreted in the context of intraspecific systematics for these taxa, the historical geology of the area, traditional nonmolecular zoogeographic information, and conservation significance. A considerable degree of phylogeographic concordance is registered with respect to (a) the configuration of intraspecific mtDNA subdivisions across turtle species, (b) the principal molecular partitions and traditional morphology-based taxonomic boundaries, (c) genetic patterns in turtles versus those described previously for freshwater fishes and terrestrial vertebrates in the region, and (d) intraspecific molecular subdivisions versus the boundaries between major zoogeographic provinces as identified by composite ranges of species in the Testudines. Findings demonstrate shared elements in the biogeographic histories of a diverse regional biota. Such phylogeographic concordances (and discordances) have ramifications for evolutionary theory as well as for the pragmatic efforts of taxonomy and conservation biology.