Phylogenetic relationships of North American phoxinins (Actinopterygii: Cypriniformes: Leuciscidae) as inferred from S7 nuclear DNA sequences.

The phylogenetic systematics of North American (NA) phoxinins, and family Leuciscidae (formerly Cyprinidae, in part) in general, have had a very dynamic history marked by uncertainty regarding the validity of many taxonomic designations. Recent molecular studies, based on mitochondrial DNA sequences, of NA phoxinins have provided the first comprehensive hypotheses for the group and suggest that they are comprised of three major lineages: creek chub-plagopterin (CC-P), western, and open posterior myodome clades. A number of phylogenetic evaluations, using both mitochondrial and nuclear DNA sequences, of the formerly recognized family Cyprinidae (=Cyprinoidea) have failed to support the traditional subfamily designations. This study, based on sequences from the first intron of the nuclear gene S7, supports many of the findings of the earlier molecular studies of NA phoxinins, but also suggests that European Leuciscidae evolved within the NA phoxinin lineage and are most likely descended from the common ancestor of the CC-P clade. As in some other recent phylogenetic studies of the Cyprinoidea, analyses of this study fail to support the broader subfamily designations within the formerly recognized family Cyprinidae.

Molecular phylogenetics of North American phoxinins (Actinopterygii: Cypriniformes: Leuciscidae) based on RAG1 and S7 nuclear DNA sequence data.

Most molecular phylogenetic hypotheses for North American (NA) phoxinins are based on mitochondrial DNA sequences (mtDNA) and the resulting hypotheses are rather variable, though there is general support for three major lineages of NA phoxinins: western, creek chub-plagopterin (CC-P), and open posterior myodome (OPM) clades. Support for a monophyletic NA phoxinin group has varied among studies. This study utilizes nuclear DNA (nDNA) sequences from the RAG1 (exon 3) and S7 (intron 1) gene regions to evaluate the phylogenetic relationships and monophyly of NA phoxinins. Results from the nDNA analyses provide overall support for the western, CC-P, and OPM clades. The CC-P clade had the best overall resolution and support in the individual and combined analyses of the nDNA data. Resolution of the western clade was fairly good, with most analyses recovering a monophyletic Gila clade. The OPM clade demonstrated the highest degree of topological variability among the analyses. The RAG1 analyses failed to recover a monophyletic NA phoxinin group by resolving the European leuciscins, inclusive Notemigonus crysoleucas, within the NA phoxinin topology. Most analyses recovered a strongly supported shiner clade though, similar to several mtDNA studies; there was a high degree of topological variability among the results.