Systematics and evolution of snubnose darters of the subgenus Ulocentra (Actinopterygii: Percidae)

Morphological variation of two species complexes of snubnose darters, Etheostoma pyrrhogaster and E. simoterum , was examined and revealed undescribed biodiversity within each complex. A new species, E. sp. Chickasaw Darter from the Forked Deer River drainage, was identified as the allopatric putative sister taxon to E. pyrrhogaster from the Obion River drainage diagnosable by pigmentation of live nuptial males, dorsal fin pattern, lateral-line scale counts, and morphometric differences. Four undescribed allopatric species were identified from the E. simoterum complex. These species were, E. sp. Tennessee Darter endemic to the Tennessee River exclusive of the upper Holston and Duck river drainages, E. sp. Duck Darter endemic to the Duck River drainage, E. sp. Westrim Darter endemic to the western Highland Rim, and E. sp. Eastrim Darter endemic to the eastern Highland Rim. Etheostoma atripinne was reelevated and found to be endemic to the Nashville Basin, leaving E. simoterum restricted to the upper Holston River drainage and Russell Fork of the Big Sandy. Species of the E. simoterum complex are diagnosable by differences in nuptial male pigmentation. Morphometric and meristic differences also provided various levels of support for the recognition of six different species within the E. simoterum complex. Replicated biogeographic pattern within the range of the complex indicates vicariance as the primary mode of speciation. A phylogenetic analysis of mitochondrial DNA sequence data indicated the Duck Darter is sister to all other species of the E. simoterum complex. The other five species are divided into a primarily Tennessee River clade sister to a primarily Cumberland River clade indicating an historical connection between the Tennessee and Cumberland rivers. Relationships within clades are largely unresolved, indicating that species within the complex have not yet reached coalescence.