INTRASPECIFIC PHYLOGEOGRAPHY OF NORTH-AMERICAN HIGHLAND FISHES - A TEST OF THE PLEISTOCENE VICARIANCE HYPOTHESIS

The highland fish fauna of eastern North America consists of Appalachi an and Ozark centers of endemism separated by the intervening Glacial Till plains. Clades within these areas are more closely related phylog enetically to each other than to clades occurring in the intervening f ormerly glaciated region, suggesting that the Pleistocene glaciations fragmented a widespread highland region and its associated fauna. Alte rnatively, it is possible that these faunal assemblages predate the gl aciations or that recent dispersals may have been more important than vicariance in determining faunal compositions. We examined the relatio nships among mitochondrial DNA (mtDNA) haplotypes within five clades o f highland fishes, each with a distribution suggestive of a Pleistocen e vicariance event. Darters of the subgenera Litocara and Odontopholis have distributions and mtDNA relationships that are consistent with t he Pleistocene integration and burial of the Teays-Mahomet valley, a m ajor drainage of the early Pleistocene. The distribution and mtDNA rel ationships among subspecies of Erimystax dissimilis are not consistent with Pleistocene vicariance, but relationships among Appalachian hapl otypes are consistent with the late Pleistocene integration of the mod ern Ohio River system. Both Cottus carolinae and the Fundulus catenatu s species group have representatives in the Mobile basin consistent wi th pre-Pleistocene divergences. Three haplotype clusters were found in C. carolinae, corresponding to the Appalachian, Ozark, and upper Kana wha River populations. However, Appalachian and Ozark F. catenatus pop ulations are paraphyletic with respect to each other. This, coupled wi th a relatively low degree of sequence divergence, suggests that no lo ng-term barriers to gene flow exist for C. carolinae and F. catenatus. These three distinct phylogeographic patterns indicate that Pleistoce ne vicariance is not the only explanation for the Appalachian-Ozark di stribution of highland fish communities.