The Marine Mammal Society’s Committee on Taxonomy currently recognizes five subspecies of blue whales: 1) the Northern hemisphere blue whale, 2) the Antarctic blue whale, 3) the Northern Indian Ocean blue whale, 4) the pygmy blue whale of the Indian Ocean, and 5) the Chilean blue whale. With the exception of the Northern Indian Ocean, where few samples are available, genetic studies using mitochondrial DNA control region (mtDNA CR) sequences and genotypes from seven microsatellite loci have identified genetic differentiation between strata considered to represent these subspecies. However, no diagnostic genetic differences between strata were found, all strata shared at least one haplotype with each of the other strata, and no distinct phylogeographic pattern was apparent in the mtDNA CR data. In other cetaceans, sequencing the full mitogenome has markedly increased taxonomic resolution, allowing clear patterns concordant with geography and/or ecotype to develop from what was originally a confusing picture. To provide more insight into the phylogeography and subspecies taxonomy of blue whales, we conducted mitogenome sequencing and SNP genotyping (~250 loci) of ~300 blue whale samples collected throughout most of the species’ range. Thus far, the picture emerging from the mitogenome data is similar but builds on results from previous studies, with significant differences identified between the Antarctic (subspecies. #2 above), Indian Ocean (subspecies #4), and Eastern South Pacific (subspecies #5) sample sets. However, no mitogenome haplotypes were shared between the three Southern Hemisphere strata (representing subspecies #2, 3, and 4) that were compared, and, unlike the results of previous studies, no significant differences were detected between the eastern North Pacific (subspecies #1) and eastern South Pacific strata (subspecies #5). Analysis of the nuclear SNP data are underway. When complete, the combined dataset is expected to further clarify our regional and global understanding of structure in blue whales.
Citation:
Lang, A., B. Hancock-Hanser, P. Morin, F. Archer, J. Calambokidis, J. P. Torres-Florez, H. Rosenbaum, R. Brownell, B. Taylor. 2017. Answers or more questions? Using high-throughput sequencing approaches to address the subspecies taxonomy of blue whales. Abstract (Proceedings) 22nd Biennial on the Biology of Marine Mammals, Halifax, Nova Scotia, October 22-27, 2017.