Hybrids, as defined by Science Daily (2013), are the result of interbreeding between two animals or plants of different taxa.
Polar Bear HybridsEdit
In 2011, a team of scientists traced mitochondrial DNA of today's polar bears to a common brown bear ancestor that lived in present-day UK during the last ice age - 20,000 to 50,000 years ago (Science Daily, 2011b). This would make modern day polar bears a sub species of Ursus arctos. This discovery could benefit future conservation strategies for both brown and polar bears. Other genetic models should that this hybridization could have occured even 70,000 to 1.5 million years ago. It was determined that polar bears and brown bears have opportunistically hybridized when climate change forced the bears to move into each others' habitat (Science Daily, 2011a). Those ancestors then went on to develop specializations suited for the frozen Arctic.
One major trait difference between brown bears and polar bears are their molar teeth. Polar bear molars are more suited for meat rather than an herbivorous diet. In order to better camouflage in the snowy and icy environment, the bears began to grow white fur (Educational Broadcasting Corporation, 2013). Polar bears also began hunting for seals rather than foraging for berries so they developed the abilities to swim and close their nostrils while underwater.
Brown bears and polar bears are still able to interbreed and created viable hybrid offspring. Though polar bears have descended from brown bears, the two species are very different and each have their own roles in their ecosystems. However, as the Arctic enviroment warms and changes, the characteristics that differentiated polar bears from their brown bear ancestors may become disadvantageous. This could mean a return to their genetic roots and the emergence of the brown bear in the less frozen Arctic.
Educational Broadcasting Corporation. (2013). Arctic Bears: How Grizzlies Evolved into Polar Bears. Retrieved from http://www.pbs.org/wnet/nature/episodes/arctic-bears/how-grizzlies-evolved-into-polar-bears/777/.
Educational Broadcasting Corporation. (2013). Video: Polar Bears Make a Difficult Decision. Retrieved from: http://www.pbs.org/wnet/nature/episodes/arctic-bears/video-polar-bears-make-a-difficult-decision/782/
Science Daily. (2011, July 7). With Climate Change, Polar Bear and Brown Bear Lineages Intertwine. Retrieved from http://www.sciencedaily.com/releases/2011/07/110707121918.htm.
Science Daily. (2011, July 8). Ancestry of Polar Bears Traced to Ireland. Retrieved from http://www.sciencedaily.com/releases/2011/07/110707121914.htm.