Genetic Evidence for a Mixed Composition of the Genus (Cottoidei: Cottidae) Necessitates Generic Realignment.

Sculpin fishes belonging to the family Cottidae represent a large and complex group, inhabiting a wide range of freshwater, brackish-water, and marine environments. Numerous studies based on analysis of their morphology and genetic makeup frequently provided controversial results. In the present work, we sequenced complete mitochondrial (mt) genomes and fragments of nuclear ribosomal DNA (rDNA) of the fourhorn sculpin and some related cottids to increase the power of phylogenetic and taxonomic analyses of this complex fish group. A comparison of the mt genomes obtained by us with other complete mt genomes available in GenBank has revealed a surprisingly low divergence (3.06 ± 0.12%) with and, at the same time, a significantly higher divergence (7.89 ± 0.16%) with the species of the genus . Correspondingly, phylogenetic analyses have shown that is clustered with but not with the species. Completely consistent patterns of divergence and tree topologies have been obtained based on nuclear rDNA. Thus, the multi-gene data in the present work indicates obvious contradictions in the relationships between the and species studied. An extensive phylogenetic analysis has provided evidence for a closer affinity of with the species of the genus than with the species of the genus . A recombination analysis, along with the additional GenBank data, excludes introgression and/or incorrect taxonomic identification as the possible causative factors responsible for the observed closer affinity between the two species from different genera. The above facts necessitate realignment of the genera and . The genetic data supports the two recognized genera, and , but suggests changing their compositions through transferring to the genus . The results of the present study resolve the relationships within a complex group of sculpin fishes and show a promising approach to phylogenetic systematics (as a key organizing principle in biodiversity research) for a better understanding of the taxonomy and evolution of fishes and for supplying relevant information to address various fish biodiversity conservation and management issues.