Patterns of diversification in a North American endemic fish, the Blackbanded Darter (Perciformes, Percidae)

The coastal plain of the south-eastern United States shows multiple biogeographic patterns of plant and animal dispersal; however, few freshwater fish taxa span these biogeographic barriers. Percina nigrofasciata, the Blackbanded Darter (Teleostomi: Percidae), is a small, benthic, freshwater fish species with an extensive range in the south-eastern United States. Recently, two species have been elevated from within P.nigrofasciata: P.crypta and P.westfalli, but their ranges have not been established. We broadly sampled across the south-eastern United States, encompassing the range of P.nigrofasciata sensu lato. We reconstruct the phylogeny of Percina using both mitochondrial and nuclear markers. Eighty-four specimens of Percina nigrofasciata were sampled for the mitochondrial gene cytochrome b (1,119bp) to form a base phylogeny. The nuclear marker S7-I1 was subsampled across populations to detect instances of hybridization. Phylogenetic relationships with other members of the genus Percina were assessed through Bayesian inference. Our results suggest that Percina nigrofasciata sensu stricto occurs from the Lake Pontchartrain Basin in Louisiana to the rivers of the Mobile Basin with little genetic structuring throughout its range. Percina westfalli occurs from the Apalachicola River drainages to the Atlantic Slope from the Savannah River to the St. Johns River. We find that P.crypta is not genetically distinct from P.westfalli in the Chattahoochee and Flint Rivers. Possible ancestral hybridization occurred between the P.nigrofasciata and P.westfalli in the panhandle of Florida between Mobile Bay and the Apalachicola River.