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 ana lyzed variation in mitochondrial DNA (mtDNA). Using 10 restriction enz ymes, eight haplotypes were identified among 95 beluga from 12 samplin g locations. The haplotypes formed two lineages, one occurring primari ly 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 Arct ic, and the eastern Beaufort Sea. The genetic difference between these lineages and the high-level genetic structure among the sample locati ons, phi(st) = 0.816 (p less than or equal to 0.0001), indicate that t hese lineages may represent the original Pacific and Atlantic ''refugi al'' stocks that colonized the Arctic after deglaciation. Further, the present segregation of these lineages between populations summering i n eastern and western Hudson Bay (p less than or equal to 0.005) is co nsistent with the hypothesis that the mitochondria of the beluga summe ring in western Hudson Bay are descended from those of a Pacific ''ref ugial'' stock and those of beluga summering in eastern Hudson Bay are descended from those of an Atlantic ''refugial'' stock. The clear diff erentiation of beluga from different summering locations provides evid ence for strong maternally directed philopatry to the summering locati ons.