| We investigated the population structure of blue whales (Balaenoptera musculus ssp.) worldwide to describe patterns of genetic differentiation and delineate biological stocks for conservation management. We examined 204 individuals from 14 locations for sequence variation primarily within the intron regions of five structural genes. A hierarchical analysis of molecular variance over all loci indicated a moderate level of substructure in the data set (weighted average phiST = 0.085). Based on pairwise comparisons and factorial correspondence analyses, we found four major subdivisions that roughly correspond to different ocean basins: the eastern North and tropical Pacific Ocean, including California, U.S.A. (N = 41), western Mexico (N = 21), western Costa Rica (N = 14), and Ecuador (N = 9); the southern Indian Ocean, including southern Australia (N = 8), western Australia (N = 15), and Madagascar (N = 6); the Southern Ocean, including regions designated as Antarctic Area I (N = 1), Area 11 (N = 8), Area III (N = 4), Area IV (N =1 3), and Area V (N = 10); and the western North Atlantic Ocean, primarily including eastern Canada (N = 38). We were unable to determine whether the eastern South Pacific Ocean, including Chile (N = 16), constituted a separate subdivision. In pairwise comparisons, Chile was not significantly different from either the eastern North and tropical Pacific Ocean or the southern Indian Ocean. Analyses of additional samples and loci may provide more resolution. |
