Recent demographic history and population structure of gray whales inferred from complete mitochondrial genomes
Anna Bruniche-Olsen, John W. Bickham, Celine A. Godard-Codding, Vladimir A. Brykov, R. Jorge Urban, J. Andrew Dewoody
International Whaling Commission
We report full mitogenome sequences for 74 North Pacific gray whales including 38 western gray whales sampled at their summer feeding grounds near Sakhalin Island and 36 eastern gray whales sampled at their wintering breeding grounds in Mexico. The relationship of these two populations is uncertain since recent studies have shown at least some western gray whales to winter in Mexico. Haplotype diversity was much higher in the large (ca. 27,000) eastern gray whale population compared to the small western gray whale population (200-300) but no phylogeographic structure is evident in the data. This is suggestive of female mediated gene flow or a recent divergence of the populations. Historical demographic analysis shows the North Pacific gray whales experienced a population bottleneck that predated the Last Glacial Maximum (LGM) but fails to resolve an expected recent population bottleneck caused by commercial whaling. Mitochondrial diversity was likely already reduced at the time of whaling.