Molecular support for marine sculpin (Cottidae; Oligocottinae) diversification during the transition from the subtidal to intertidal habitat in the Northeastern Pacific Ocean

Sculpins in the genera Ruscarius, Artedius, Clinocottus, and Oligocottus are common intertidal and subtidal benthic fishes of the Northeastern Pacific Ocean. While there has been a long history of attempts to reconstruct the evolutionary relationships within this clade, studies have largely resulted in conflicting conclusions. Current ideas regarding the limits of species and genera in this subfamily (Oligocottinae) and their branching order are based primarily on morphology [Bolin, R.L., 1944. A Review of the Marine Cottid Fishes of California. Natural History Museum of Stanford University, Stanford University, California; Bolin, R.L., 1947. The Evolution of the Marine Cottidae of California with a Discussion of the Genus as a Systematic Category. Stanford University, California]. The primary objectives of this study are: (a) to determine if the phylogenetic relationships inferred from DNA characters are concordant with those inferred from morphological characters and (b) to determine if a habitat shift from the subtidal to the intertidal environment resulted in the diversification of the group. Cytochrome b and Nicotinamide Adenine Dinucleotide Dehydrogenase subunit one mitochondrial gene fragments and one nuclear intron (S7 ribosomal protein) were sequenced in order to infer the phylogenetic relationships within this subfamily. Maximum likelihood and Bayesian algorithms were employed to reconstruct phylogenetic trees. We found that several genera in this clade are not monophyletic and that there is a clear phylogenetic signal indicating that a habitat shift from the subtidal to the intertidal habitat has resulted in the diversification of the Oligocottinae.