Phylogeography, Population Structure, and Dispersal Patterns of the Beluga Whale in the Western Nearctic Revealed by Mitochondrial DNA
May 17, 1997
Examination of population genetic structure and movement patterns of beluga whales in Alaska and northwest Canada using nucleotide sequence variation within the mitochondrial genome's control region.
The recent evolutionary history, population structure, and movement patterns of beluga whales in the western Nearctic were inferred from an analysis of mitochondrial DNA control region sequence variation of 324 whales. These whales were from 32 locations representing five summer concentration areas in Alaska and northwest Canada. Phylogenetic relations among haplotypes were inferred from parsimonious networks. The genetic subdivision was examined using haplotypic frequency-based indices and an analysis of variance method modified for use with interhaplotypic distance data. MtDNA relationships were characterized by a series of star-like phylogenies. When viewed in conjunction with information on haplotype frequency and distribution, these phylogenies suggested a rapid radiation of beluga whales into the western Nearctic following the Pleistocene, and an early divergence of the Beaufort Sea from the Chukchi and Bering Seas subpopulations.
Overall, nucleotide diversity was low (.51%), yet all major summering concentrations were significantly differentiated from one another. Stratification of samples by gender and age from the three northernmost subpopulations suggested that female cohorts from neighboring subpopulations were more differentiated than males. Further stratification of adult animals by age revealed that older adults were substantially less subdivided among locations than younger adults. This was particularly true for males, suggesting that dispersal, although limited, is biased toward older adult males. Overall the patterns of mtDNA variation in beluga whales indicated that the summering concentrations are demographically, if not phyletically, distinct. Population structure appears to be maintained primarily by natal homing behavior. Asymmetries in dispersal may be associated with the type of mating system.
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G. M. O'Corry-Crowe, R. S. Suydam, A. Rosenberg, K. J. Frost, and A. E. Dizon. Published in Molecular Ecology, 6, 995-970, 1997.