Phylogenetic relationships of major clades of Catostomidae (Teleostei : Cypriniformes) as inferred from mitochondrial SSU and LSU rDNA sequences

Suckers (Family Catostomidae) are holarctic in distribution and include 76 recent species in 14 genera, with 13 genera and 75 species occurring in Nor th and Central America and Siberia. Although this group constitutes a signi ficant component of many aquatic ecosystems, most historic systematic effor t 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 li fe history characters has advanced current understanding of relationships a mong 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 monoph yletic Catostomidae, Ictiobinae, and Catostominae and para- or polyphyletic Cycleptinae, with Myxocyprinus as the basal-most taxon and Cycleptus as ei ther the next most-basal taxon or the taxon basal to the Catostominae. Rela tionships within the Catostominae were generally consistent with those prop osed in the above-noted recent phylogenetic study although Thoburnia and Hy pentelium were either a clade sister to or a grade group relative to Moxost oma and Scartomyzon. In all trees, Scartomyzon was paraphyletic and embedde d within Moxostoma. Phylogenetic affinities of Erimyzon and Minytrema varie d 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: formati on 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 Scartomyzo n; Erimyzon and Minytrema are incertae sedis within Catostominae; and resur rection of the tribe Thoburniini, containing Thoburnia and expanded to incl ude Hypentelium. (C) 2001 Academic Press.