Temporal stability and fine-scale spatial structure in mtDNA haplotypes of humpback whales on feeding grounds in the eastern North Pacific
Karen Lohman, Debbie Steel, John Calambokidis, Bruce Mate, Daniel M. Palacios, Jim Rice and C. Scott Baker
International Whaling Commission
Here, we assess the temporal stability and geographic differentiation of mtDNA haplotypes from humpback whales on the eastern North Pacific feeding grounds using thirty-one years (1988-2019) of biopsy sampling effort (n=951). Genotype matching with standard DNA profiles (i.e., mtDNA haplotypes, 10 microsatellite loci and sex) identified n=777 individuals among the total collection. This includes a substantial increase in the number of individuals sampled in previously underrepresented feeding areas along the coasts of Oregon (n=49) and Northern California (n=40). Pairwise comparisons of mtDNA haplotype frequencies across three temporal strata showed no significant differences for Central California, the geographic region with the most extensive temporal sampling coverage. Tests of geographic differentiation considered six regional strata: Northern British Columbia (NBC), Southern British Columbia/Washington (NBC/WA), Oregon (OR), Northern California (N-CA), Central California (C-CA), and Southern California (S-CA). All pairwise comparisons were significant, except the comparison between Northern CA and OR. These results revealed a greater degree of geographic structure in these feeding grounds than previously assumed. The results also provide new evidence for the temporal stability and fine-scale maternal fidelity of humpback whales to feeding grounds along the eastern North Pacific. Further analyses are underway to improve assignment of individuals from feeding grounds to breeding grounds using nuclear genetic markers.