Systematics and Taxonomy of the Snubnose Darter, Etheostoma simoterum (Cope)

Abstract

Abstract A taxonomic revision of Etheostoma simoterum (Cope) published in 2007 resulted in the recognition of six species, with two species distributed in the Tennessee River system. A newly defined Etheostoma simoterum was restricted to populations in the Holston River above the confluence of the North and South Forks, and the Russell Fork system of the Ohio River drainage. A newly described species, Etheostoma tennesseense Powers & Mayden, included all other populations historically considered Etheostoma simoterum in the Tennessee River system from near the mouth of the Duck River upstream to the Clinch River, including the Holston River below the forks. A subsequent study utilizing molecular phylogenetics and analysis of male nuptial coloration did not support the recognition of Etheostoma tennesseense. Molecular phylogenies resolve both Etheostoma simoterum and Etheostoma tennesseense as paraphyletic. In addition, it was determined that male coloration patterns are not diagnostic for the more restricted and new definition of Etheostoma simoterum. In this study, we examine the systematics of Etheostoma simoterum using meristic traits sampled from more than 1,000 specimens, including Cope's syntype series of Hyostoma simoterum and Powers and Mayden's paratopotype series of Etheostoma tennesseense. Our results show a pattern of clinal variation, where meristic traits are higher in the in the lower Tennessee River system. Comparisons of populations above and below the forks of the Holston River show no differences in meristic traits, but populations sampled from the Watauga River system exhibit scale counts lower than any other population of Etheostoma simoterum. We cannot reject the hypothesis that Etheostoma tennesseense is conspecific with the specimens that comprise the Hyostoma simoterum syntype series. Based on both morphological and molecular species delimitation strategies, we treat Etheostoma tennesseense as a synonym of Etheostoma simoterum.