Systematics and Biogeography of the Tennessee Shiner, Notropis leuciodus (Cope) (Teleostei: Cyprinidae)

Abstract

Samples collected from throughout the range of the Tennessee shiner, Notropis leuciodus, were examined electrophoretically for patterns of variation at 47 presumptive gene loci. Statistically significant genic heterogeneity occurred at 24 of the 30 polyallelic loci. Patterns of allelic variability and phylogenetic relationships within N. leuciodus are consistent with the isolation and divergence of forms endemic to the Green, Cumberland, lower Tennessee, middle Tennessee, Hiwassee, and tributaries of the upper Tennessee rivers exclusive of the Hiwassee River. The oldest divergence in this clade is identified between the Green River and CumberlandTennessee River clades. Within the latter clade, N. leuciodus from the lower Tennessee River constitutes the sister group to a clade inclusive of populations from the middle Tennessee, Hiwassee, and upper Tennessee rivers. Biogeographically, the identified patterns of divergence and genealogical relationships within N. leuciodus are consistent with an early Tertiary origin of the clade in pre-Pleistocene river systems. An alternative, late Tertiary-Pleistocene explanation for diversification in the complex, involving dispersal and isolation with river captures, is provided.