Comparative Shape of Two Recently Diverged Species of Pacific Rockfish: Sebastes ciliatus and S. variabilis

Abstract

Species delimitation can be based on the consideration of several different criteria, including the differentiation of ecological or functional traits. Two species of Pacific rockfish, the dark rockfish (Sebastes ciliatus) and the dusky rockfish (Sebastes variabilis), appear to represent recently divergent evolutionary lineages. We evaluate evidence for the differentiation of these two species in somatic shape using geometric morphometrics at two locations in the northeast Pacific where they occur in sympatry. The somatic shape was significantly different between species, but the species’ shape did not vary between the two locations. Sebastes ciliatus had an upturned and relatively smaller head, eye, and jaw, and an elongated midbody, whereas S. variabilis had a downturned and larger head, eye, and jaw, and a shorter midbody. These results suggest that S. ciliatus and S. variabilis are morphometrically differentiated in a similar way in both locations. The somatic shape differentiation between these two sympatric species is similar to genus-wide patterns of somatic shape differentiation.