Population Genetic Structure of Beluga Whales Delphinapterus leucus Mitochondrial DNA Sequence Variation Within and Among North American Populations

Abstract

Beluga whales are migratory over much of their range, congregating in small groups around shallow river estuaries in summer, and overwintering in large groups in areas with reliable open water. This complicates management issues because it is unclear if belugas from the common wintering ground represent one large group with exchange of individuals, or if each summer estuarine concentration should be managed as a separate stock. To examine the genetic structuring, we analyzed variation in mitochondrial DNA (mtDNA) restriction sites among 101 beluga whales from 10 regions across North America, including Greenland. Using 11 restriction enzymes, 9 haplotypes were identified among 71 whales. The remaining 30 whales were tested with only the six restriction enzymes found to identify polymorphisms. We found a marked segregation of divergent haplotypes for both sexes between eastern and western Hudson Bay. Haplotype 1 was found in 19 out of 21 animals on the east coast, while haplotype 5 was found in 18 out of 20 animals on the west coast. Sequence divergence among the 71 belugas was estimated to be 2.03%. Haplotypes fell into two major phylogenetic groups, labelled lineage I and II. Lineage I haplotypes occurred primarily in the St. Lawrence Estuary and the eastern Hudson Bay. Lineage II haplotypes occurred primarily along the western Hudson Bay, Southern Baffin Island, western Greenland, the Canadian high arctic, and the Beaufort Sea. These findings support the hypothesis that belugas exhibit maternally directed philopatry to summering grounds, and are consistent with the hypothesis that after deglaciation, the arctic was recolonized by at least two stocks of belugas divergent in their mtDNA, possibly representing Atlantic and Pacific stocks.