I'm sure lots of you have been watching BBC's Frozen Planet (if not, have a look). Here's a short clip to introduce the little guys that will be staring this blog post...
...Okay, enough baby polar bears, let's get down to business! My previous post mentioned how long term isolation in refugial areas exposes plants and animals to different selection pressures, possibly leading to speciation. Speciation under these circumstances is much more likely to occur in populations in cryptic Northern refugia during glacial periods than those in Southern refugial areas during interglacials (because glacials tend to be longer than interglacials). Stewart et al (2010), therefore, point out that it is interesting to consider the role of cryptic Northern refugia for the evolution of Arctic species, like the polar bear. Genetic evidence has proven that the polar bear evolved from the brown bear within the last 200-300 thousand years ago.
Here’s a quick clip of some brown bears for comparison…
Polar bears have evolved unique characteristics for Arctic life including hollow, transparent fur and black skin (for a full list of adaptations click here). For these adaptations to have occurred, a brown bear population must have been exposed to colder, Northern climates where they had access to the ocean. Stewart et al (2010) suggest that this population of brown bears lived in a cryptic Northern refugium where they were reproductively isolated and allopatric speciation occurred. It is also likely that the Arctic fox evolved from the swift fox in this way. These examples show that cryptic Northern refugia not only produce genetic diversity but are most probably capable of creating new species as well! It’s just a shame that this ‘new’ species is so threatened by the effects of anthropogenic global warming…
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