Geographic variation in the skull of the ringed seal, Pusa hispida

Abstract

A sample of 244 ringed seal (Pusa hispida) skulls from 7 localities was examined morphometrically to describe the pattern of geographic variation and to assess subspecies-level taxonomy. Analyses of covariance revealed significant differences among specimens from Lake Saimaa, Lake Ladoga, and other areas. Saimaa seals are robust and short in the skull portion related to feeding, whereas Ladoga seals have narrower skulls and smaller bulla. On scatter plots of canonical discriminant scores obtained using size-free scores, Ladoga and Saimaa specimens were almost separated, but other specimens overlapped and could not be distinguished. Saimaa seals were the most distant, followed by Ladoga seals in the unweighted pair-group method using arithmetic average clustering and neighbor-joining phenograms. These results showed that although ringed seals from Lake Ladoga and Saimaa were considerably differentiated, specimens from other localities were not distinguishable from each other, suggesting similar selection pressure or extensive gene flow especially in the Arctic basin. Further recognition of subspecies for the Arctic seals was not supported.