Population Structure of the Blue Whale ( Balaenoptera musculus ) Based on Nuclear Genetic Variation
We explored the variation in functional nuclear genes using single stranded conformational polymorphisms (SSCP) to determine the stock structure of blue whales for conservation management. Our sample set included individuals from 10 locations: California/Mexico (N=61); Central America (N=11) (samples primarily collected during late November); Galapagos Islands (N=11) (early November); Chile (N=14) (mid December to early January); western North Atlantic Ocean (N=41); southwestern Indian Ocean (N=7) (mid to late December); Australia (N=10) (mid December to mid June); Antarctic Area I (N=1); Antarctic Area II (N=8); Antarctic Area III (N=2); and Antarctic Area IV (N=10). We found population substructure based on a survey of three loci: an intron in the cholinergic receptor gene (CHRNA1) (19 alleles); an intron in the polymerase beta gene (POLB) (5 alleles); and an exon in the proviral integration site gene family (PIM1) (5 alleles). Data were analyzed using the computer programs FSTAT 2.9.1 (Goudet) and Genepop (web version) (Raymond and Rousset). Population subdivision was significant over all loci as measured by Weir and Cockerham's (1984) FST statistic (theta=.089). We conducted pairwise differentiation tests between locations and found four evolutionarily divergent groups (p=.0001): the western North Atlantic Ocean, the eastern Pacific Ocean (includes the sample locations of California/Mexico, Central America, Galapagos Islands, and Chile), the Indian Ocean (includes the sample locations of the southwestern Indian Ocean and Australia), and the Southern Ocean (includes Antarctic Areas II and IV). So far, we found no significant differences among locations within these groups, but this may be due to low sample size at many locations. The analysis of additional samples may indicate separate breeding stocks within these groups. To achieve further resolution, we will sequence allelic variants at each locus and analyze the variation at two additional polymorphic nuclear genes.
Conway, C., L. Lyons, R. Sears, J. Calambokidis, P. Gill, and B. May. 2001. Population Structure of the Blue Whale ( Balaenoptera musculus ) Based on Nuclear Genetic Variation. Poster presented at the 14th biennial conference on the Biology of Marine Mammals, Vancouver, Canada , November 28 – December 3, 2001.