Phylogenetic relationships of Moxostoma and Scartomyzon (Catostomidae) based on mitochondrial cytochrome b sequence data

Abstract

A recent phylogenetic study based on morphological, biochemical and early life history characters resurrected the genus Scartomyzon (jumprock suckers, c. eight−10 species) from Moxostoma (redhorse suckers, c. 10–11 species) and advanced the understanding of relationships among species in these two genera, and the genealogical affinities of these genera with other evolutionary lineages within the tribe Moxostomatini in the subfamily Catostominae. To further examine phylogenetic relationships among moxostomatin suckers, the complete mitochondrial (mt) cytochrome b gene was sequenced from all species within this tribe and representative outgroup taxa from the Catostomini and other catostomid subfamilies. Phylogenetic analysis of gene sequences yielded two monophyletic clades within Catostominae: Catostomus+Deltistes+Xyrauchen+Erimyzon+Minytrema and Moxostoma+Scartomyzon+Hypentelium+Thoburnia. Within the Moxostomatini, Thoburnia was either unresolved or polyphyletic; Thoburnia atripinnis was sister to a monophyletic Hypentelium. In turn, this clade was sister to a monophyletic clade containing Scartomyzon and Moxostoma. Scartomyzon was never resolved as monophyletic, but was always recovered as a polyphyletic group embedded within Moxostoma, rendering the latter genus paraphyletic if ‘Scartomyzon’ continues to be recognized. Relationships among lineages within the Moxostoma and‘Scartomyzon’clade were resolved as a polytomy. To better reflect phylogenetic relationships resolved in this analysis, the following changes to the classification of the tribe Moxostomatini are proposed: subsumption of‘Scartomyzon’into Moxostoma; restriction of the tribe Moxostomatini to Moxostoma; resurrect the tribe Erimyzonini, containing Erimyzon and Minytrema, classified as incertae sedis within Catostominae; retain the tribe Thoburniini.