Evolution of a mitochondrial cytochrome b gene sequence in the species-rich genus sebastes (Teleostei, Scorpaenidae) and its utility in testing the monophyly of the subgenus Sebastomus.

The ecologically diverse and species-rich rockfishes (Sebastes) are a useful group for the study of marine speciation. The monophyly of the genus is generally accepted, as is the validity of most of the numerous species found along the West Coast of North America. However, the subgeneric groupings that would help in the proposal and interpretation of various speciation schemes are poorly supported based on widely overlapping morphological characters. The use of genetic characters provides an alternative approach. In this study, we present the first quantitative analysis supporting the monophyly of all 14 species of the subgenus Sebastomus among 54 congeners. The structural features and evolution of the 750 bp of the cytochrome b gene used to test the monophyly were similar to those of other vertebrates. Low levels of intrageneric sequence divergence (<10%) and incipient levels of saturation at third-codon positions were found in the gene. The monophyly of Sebastomus was supported in extensive phylogenetic analyses using distance, cladistic, and likelihood methods. Further corroboration was obtained from permutation- and simulation-based statistical tests.