Gene flow on ice: the role of sea ice and whaling in shaping Holarctic genetic diversity and population differentiation in bowhead whales (Balaena mysticetus)


  • Ancient DNA and genetic data collection and analysis was funded by the US National Marine Fisheries Service and North Slope Borough Wildlife Management Authority in addition to several small awards to HCR. SEA was funded through a fellowship provided by NRDC. The sampling of whales in Greenland was funded by the Greenland Institute of Natural Resources, the Commission for Scientific Research in Greenland, the Danish Cooperation for the Environment in the Arctic under the Danish Ministry of Environment and the Department of Fisheries and Oceans.


S. Elizabeth Alter, Department of Biology, York College, City University of New York, 94-20 Guy R. Brewer Blvd, Jamaica, New York 11415. Tel: +718-262-2732; Fax: +718-262-2369; E-mail:

Howard C. Rosenbaum, Wildlife Conservation Society, Global Conservation Program-Ocean Giants Program, 185th St and Southern Blvd, Bronx, New York, 10460. Tel: 718-220-5184; Fax 718-364-4275; Email:


Sea ice is believed to be a major factor shaping gene flow for polar marine organisms, but it remains unclear to what extent it represents a true barrier to dispersal for arctic cetaceans. Bowhead whales are highly adapted to polar sea ice and were targeted by commercial whalers throughout Arctic and subarctic seas for at least four centuries, resulting in severe reductions in most areas. Both changing ice conditions and reductions due to whaling may have affected geographic distribution and genetic diversity throughout their range, but little is known about range-wide genetic structure or whether it differed in the past. This study represents the first examination of genetic diversity and differentiation across all five putative stocks, including Baffin Bay-Davis Strait, Hudson Bay-Foxe Basin, Bering-Beaufort-Chukchi, Okhotsk, and Spitsbergen. We also utilized ancient specimens from Prince Regent Inlet (PRI) in the Canadian Arctic and compared them with modern stocks. Results from analysis of molecular variance and demographic simulations are consistent with recent and high gene flow between Atlantic and Pacific stocks in the recent past. Significant genetic differences between ancient and modern populations suggest PRI harbored unique maternal lineages in the past that have been recently lost, possibly due to loss of habitat during the Little Ice Age and/or whaling. Unexpectedly, samples from this location show a closer genetic relationship with modern Pacific stocks than Atlantic, supporting high gene flow between the central Canadian Arctic and Beaufort Sea over the past millennium despite extremely heavy ice cover over much of this period.