Phylogenetic Relationships of Major Clades of Catostomidae (Teleostei: Cypriniformes) as Inferred from Mitochondrial SSU and LSU rDNA Sequences

Abstract

Suckers (Family Catostomidae) are holarctic in distribution and include 76 recent species in 14 genera, with 13 genera and 75 species occurring in North and Central America and Siberia. Although this group constitutes a significant component of many aquatic ecosystems, most historic systematic effort has been either alpha- or limited beta-level studies focusing on the two largest tribes within the family, the Catostomini and the Moxostomatini. A recent phylogenetic study based on morphological, biochemical, and early life history characters has advanced current understanding of relationships among catostomid fishes. To further examine phylogenetic relationships among basal lineages of catostomids, we sequenced the entire mitochondrial (mt) SSU and LSU rRNA genes from genera representing all subfamilies and tribes within Catostomidae. Phylogenetic analysis of gene sequences yielded monophyletic Catostomidae, Ictiobinae, and Catostominae and para- or polyphyletic Cycleptinae, with Myxocyprinus as the basal-most taxon and Cycleptus as either the next most-basal taxon or the taxon basal to the Catostominae. Relationships within the Catostominae were generally consistent with those proposed in the above-noted recent phylogenetic study although Thoburnia and Hypentelium were either a clade sister to or a grade group relative to Moxostoma and Scartomyzon. In all trees, Scartomyzon was paraphyletic and embedded within Moxostoma. Phylogenetic affinities of Erimyzon and Minytrema varied depending on data set and character weighting scheme employed. To better reflect phylogenetic relationships resolved in this extensive analysis, we propose the following changes to the classification of catostomids: formation of the new subfamily Myxocyprininae, containing Myxocyprinus from China; restriction of the Cycleptinae to the two species of Cycleptus from North America; restriction of the tribe Moxostomatini to Moxostoma and Scartomyzon; Erimyzon and Minytrema are incertae sedis within Catostominae; and resurrection of the tribe Thoburniini, containing Thoburnia and expanded to include Hypentelium.