Influence of Holocene habitat availability on Pacific gray whale (Eschrichtius robustus) population dynamics as inferred from whole mitochondrial genome sequences and environmental niche modeling

Environmental changes since the Pleistocene and commercial whaling in the last few centuries have drastically reduced many whale populations, including gray whales in the North Pacific. Herein we use complete mitogenome sequences from 74 individuals to evaluate gray whale phylogeography and historical demography, then use environmental niche modeling to assess how habitat availability has changed through time for Pacific gray whales. We identify a large degree of haplotype sharing between gray whales sampled in Russian and Mexican waters, coupled with very limited matrilineal population structure. Confirming previous studies, our environmental niche models showed a decrease in available habitat during the Last Glacial Maximum, but we find no genetic signals of recent population declines in mitochondrial genomes despite both sustained habitat loss and a commercial whaling bottleneck. Our results illustrate the complex dynamics of baleen whale biogeography since the Holocene as well as the difficulty in detecting recent demographic bottlenecks from mitochondrial DNA sequences.

Automated summary

Environmental changes and commercial whaling have significantly reduced whale populations, including gray whales in the North Pacific. However, genetic signals of recent population declines have not been detected despite sustained habitat loss and a commercial whaling bottleneck. Large haplotype sharing between gray whales in Russian and Mexican waters suggests limited population structure.