UAS Faculty Dr. Dave Tallmon co-authors Nature commentary on threat to polar biodiversity

Global warming may be leading to hybrid offspring in Arctic mammals including whales, seals and bears

Juneau, Alaska

Date of Press Release: December 20, 2010

In a commentary article published in the December 16, 2010 edition of the international science journal Nature, University of Alaska Southeast Biology and Marine biology faculty David Tallmon and two co-authors say global warming may be leading to hybrid offspring in Arctic mammals including whales, seals and bears.  Receding sea ice decreases habitat and increases contact with previously separated species. This trend “could push some species over the edge towards extinction” said Tallmon. “Once hybridization occurs it is essentially irreversible. Once that happens it is impossible to recover that creature.”

Co-author Andrew Whiteley worked with Tallmon on post-graduate studies at the University of Alaska Southeast.  He looked into the possible impacts on breeding and food from the loss of summer sea ice. Whiteley is now a conservation geneticist at the University of Massachusetts at Amherst. The lead author is University of Alaska evolutionary biologist Brendan Kelly based at the National Oceanic and Atmospheric Administration’s Marine Mammal lab in Juneau. Kelly is a former Dean of Arts and Sciences at UAS.

In the article, “The Arctic melting pot” Kelly, Whiteley and Tallmon give anecdotal examples of hybrid species of Arctic mammals.  The hybrid species garnering the most recent attention are known as “grolar” or “pizzly” bears, the result of polar bears mating with grizzly bears. They write, “The Arctic Ocean is predicted to be ice-free in summer before the end of the century, removing a continent-sized barrier to interbreeding. Polar bears are spending more time in the same areas as grizzlies; seals and whales currently isolated by sea ice will soon be likely to share the same waters.”  The disappearance of the Arctic ice cap is removing a barrier to interbreeding that has existed for at least 10,000 years. The authors conclude that species strong enough to thrive in the extreme conditions of the Arctic due to adaptive genes will be weakened by interbreeding. “If polar bears survive climate change in the secluded refuges-which is far from certain-interbreeding could be the final straw,” they write.

Under the Endangered Species Act, there is no official policy for dealing with hybrid species. Tallmon, Kelly and Whiteley recommend that the International Union for the Conservation of Nature develop a policy to limit or prevent hybridization.

The genesis of the article goes back to 2008, when Brendan Kelly asked Tallmon to work with UAS undergraduate Marine Biology student Micaela Ponce on ring seal genetics on the North Slope and the impacts of receding ice on the species. Ponce is currently working on her PhD at the University of Michigan.