Unusual population of brown bears on Alaskan islands turns
out to have a remarkable and revealing history
At the end of the last ice age, a population of polar bears
was stranded by the receding ice on a few islands in southeastern Alaska. Male
brown bears swam across to the islands from the Alaskan mainland and mated with
female polar bears, eventually transforming the polar bear population into
brown bears.
Evidence for this surprising scenario emerged from a new
genetic study of polar bears and brown bears led by researchers at the
University of California, Santa Cruz. The findings, published March 14 in PLOS
Genetics, upend prevailing ideas about the evolutionary history of the two
species, which are closely related and known to produce fertile hybrids.