Patterns of genetic variation within and among natural populations reflect the contributions of historical and contemporary processes. In an area of study called phylogeography, my laboratory uses molecular markers to evaluate the distribution of variation among populations of freshwater fishes and assesses the relative roles of vicariance, dispersal, contemporary gene flow, and fisheries management practices in that distribution. Some of our recent and ongoing projects include.

1. In cooperation with the states of Kentucky and West Virginia, we are using mitochondrial DNA sequence variation and microsatellite DNA variation to study differentiation among native and introduced walleye (Sander vitreus) populations. Several native populations have been identified and we are examining the magnitude of introgression with introduced populations. One goal is to identify populations that could be used to reestablish other native populations. A parallel study of sauger (Sander canadense) allows us to examine differentiation in a closely-related species much less influenced by hatchery introductions.

3. Studies of populations of freshwater lampreys in the genus Lampetra using mtDNA sequence variation have demonstrated highly significant differentiation among populations yet many of these populations show little to no morphological variation.  Our data suggest that many of these populations have been isolated since the Pliocene. We hope to use this data to identify undescribed forms of this widespread species. We are further clarifying patterns of differentiation in these lampreys by examining the evolution and distributions of tandem repeats in the mitochondrial control region.

4. We have begun an analysis of patterns of variation in the Ohio musky (Esox masquinongy ohioensis), a sub-species endemic to the Ohio River drainage. We are evaluating DNA sequence variation across its range and in a larger phylogeographic context. We are incorporating microsatellite DNA variation to understand differentiation among hatchery strains used by Ohio, Pennsylvania, Kentucky, and West Virginia.