Scientists Link DNA Of Polar And Brown Bears

Science Watch, Bear Hunting Magazine
03/16/2013

A report released earlier this week attempted to clarify past studies on a population of Alaskan brown bears that are genetically similar to polar bears, yet look and act like typical brown bears.

"This population of brown bears stood out as being really weird genetically, and there’s been a long controversy about their relationship to polar bears,” stated a professor of ecology and evolutionary biology. “We can now explain it, and instead of the convoluted history some have proposed, it’s a very simple story.”

The group of scientists believe that as the last Ice Age ended and the glaciers receded, a group of polar bears were stranded on Alaska’s Admiralty, Baranof, and Chicagof Islands (ABC Islands). Eventually, male brown bears swam across to the islands and mated with female polar bears living there. This slowly transformed the entire ABC Islands’ population into brown bears.

“The key to solving this mystery was to analyze DNA from the ABC Islands bears’ nuclear genomes, and in particular their X-chromosomes,” the scientists stated. “Focusing on the X gave us a surprising result.”

The team, which included scientists from California, Canada and Russia, analyzed DNA from seven polar bears, an ABC Islands brown bear, a mainland brown bear and a black bear. The researchers also considered data from recently published bear studies by others.

The team found that polar bears are genetically homogeneous, with no evidence of brown bear ancestry, yet the ABC Islands brown bear DNA contained clear evidence of polar bear ancestry. According to their evidence from the bears’ X chromosome, it indicated that ABC brown bears have more DNA in common with polar bear females than they do with polar bear males.



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