Phylogeography of Central Highlands fishes: Discovering cryptic diversity and ancient drainage patterns in North America

The Central Highlands of eastern North America contain a strikingly diverse assemblage of temperate freshwater fishes and have long been a focus of biogeographic studies. Diversity and distribution of this ichthyofauna have been traditionally explained by competing hypotheses of dispersal and vicariance. However, recent studies based on large genetic data sets have challenged these hypotheses. I examined genetic variation in four unrelated clades of Central Highlands fishes to assess the roles of dispersal and vicariance in shaping diversity and distribution within these groups. I assembled complete cytochrome b gene mtDNA sequence data sets for individuals across the range of Hypentelium nigricans (northern hogsucker), Notropis rubellus species group (rosyface shiner complex), Hybopsis amblops (bigeye chub) and Etheostoma blennioides species group (greenside darter complex). Phylogeographic analyses included Bayesian and parsimony analyses and demographic analyses included mismatch plots. Pairwise genetic divergences were calculated and divergence dates for clades were estimated. Results of these analyses revealed ancient cryptic diversity that existed prior to the onset of Pleistocene glaciations supporting hypotheses of preglacial drainage patterns in eastern North America. Common patterns across clades include both ancient and recent vicariant events and population expansion into previously glaciated regions. Although there are common patterns, each clade responded differently to climatic change and drainage rearrangement resulting in complex patterns of phylogeographic history. Results from these studies have changed our understanding of the historical biogeography of Central Highlands fishes.