While the prizzly, a cross between a polar bear and a grizzly bear, may seem interesting at first, this hybrid, along with others, could destroy the gene pool of the two contributing species and result in a new type of animal that is more vulnerable to threats.
One of the biggest such threats, which is also an instigator of hybridization, is rapidly melting Arctic sea ice, the authors believe.
It “imperils species through interbreeding as well as through habitat loss,” authors Brendan Kelly, Andrew Whiteley and David Tallmon argue. “As more isolated populations and species come into contact, they will mate, hybrids will form and rare species are likely to go extinct. As the genomes of species become mixed, adaptive gene combinations will be lost.”
Kelly, a researcher at NOAA’s National Marine Mammal Laboratory in Juneau and his colleagues have identified at least 34 possible hybridizations that could occur among animals in and around the Arctic.
The prizzly was confirmed by DNA in 2006. This was after a white bear with patches of brown fur was shot by hunters. In the late 1980′s, a whale thought to be a narwhal-beluga mix turned up in west Greenland. Just last year, an apparent bowhead-right whale hybrid was photographed in the Bering Sea between Alaska and Russia.
The authors add that “Dall’s porpoises are known to be mating with harbor porpoises off the coast of British Columbia, and seal hybrids have been identified in museum specimens and in the wild.” The researchers further note: “There is evidence of hybridization across species (such as between spotted and harbor seals) as well as across genera (such as hard and hooded seals).”
Despite the problems with such hybrids, this is actually the semi-good news. The bad is that most cross-species matings don’t even produce any viable offspring, so adult polar bears, whales, porpoises and other animals could mate multiple times and still die without having reproduced.
Hybridization does occur naturally in the wild. DNA studies, for example, suggest that our ancient human ancestors interbred, with Neanderthals possibly being absorbed into our gene pool and disappearing as their own distinct hominid species.
“But hybridization driven by human activities tends to occur quickly and to reduce genomic and species diversity,” Kelly and his team write. “When mallard ducks were introduced to New Zealand in the 1860s, they began mating with native gray ducks. Now few, if any, pure native populations remain.”
In the Arctic, the North Pacific right whale and polar bears are probably threatened the most by hybridization. According to the Nature commentary, fewer than 200 North Pacific right whales exist now. If they continue to mate with bowhead whales, goodbye North Pacific rights.
To help combat the growing problem of hybridization in the Arctic, Kelly, Whiteley and Tallmon advise that scientists “should combine models of sea-ice loss, oceanography and landscape genomics to predict when and where hybridization is most likely, and to monitor the genetics of at-risk populations.”
They add: “National and tribal governments should work together. Some indigenous groups actively monitor the harvests of Arctic marine mammals, and they could collect genetic samples in remote areas.”
“The rapid disappearance of sea ice leaves little time to lose.”
Top photo: Polar Bear; Credit: Patricia Rockwell. Middle photo: Grizzly Bear, Credit: U.S. Fish and Wildlife Service. Bottom photo: Prizzly from the Rothschild Museum, Tring, England; Credit: Sarah Hartwell