Population genetic structure of beluga whales (Delphinapterus leucas): Mitochondrial DNA sequence variation within and among North American populations

Beluga whales (Delphinapterus leucas) are migratory over much of their range, congregating in small groups around shallow river estuaries in summer and overwintering in areas of broken pack ice. To investigate the potential genetic structuring within North American beluga, we analyzed variation in mitochondrial DNA (mtDNA). Using 10 restriction enzymes, eight haplotypes were identified among 95 beluga from 12 sampling locations. The haplotypes formed two lineages, one occurring primarily in whales from the St. Lawrence estuary and eastern Hudson Bay and the other primarily in beluga sampled in the waters of western Hudson Bay, southern Baffin Island, western Greenland, the Canadian High Arctic, and the eastern Beaufort Sea. The genetic difference between these lineages and the high-level genetic structure among the sample locations, phi(st) = 0.816 (p less than or equal to 0.0001), indicate that these lineages may represent the original Pacific and Atlantic ''refugial'' stocks that colonized the Arctic after deglaciation. Further, the present segregation of these lineages between populations summering in eastern and western Hudson Bay (p less than or equal to 0.005) is consistent with the hypothesis that the mitochondria of the beluga summering in western Hudson Bay are descended from those of a Pacific ''refugial'' stock and those of beluga summering in eastern Hudson Bay are descended from those of an Atlantic ''refugial'' stock. The clear differentiation of beluga from different summering locations provides evidence for strong maternally directed philopatry to the summering locations.