What I end up seeing, in this quintessentially 21st century creature, is a glimpse of the future.
— Gamble (2012): One, two, three, er…many. in The Last Word on Nothing.
The effect of rapid Arctic warming on polar bears has been a theme this year in Environmental Science, so this article on the hybridization of polar bears and grizzly bears caught my eye.
As caribou migration routes have moved North, grizzlies have followed and started mating with polar bears. Not only have they produced hybrid young, but those young are fertile. Polar bears and grizzlies only diverged about 150,000 years ago and haven’t developed many genetic differences, despite quite dramatic visual dissimilarities. Second-generation hybrids have now been confirmed in the wild.
This article is also of note to my Middle School science class because we’ve talked about speciation — the divergent evolution of two populations into separate species — before when we looked at the phylogenetic tree and bison evolution in particular. This seems to be a re-convergence after separation. As the climate warms the grizzly bears are able to range further north, while the polar bears are more restricted to the shores by the melted sea ice, so the two populations encounter each other more and more. Thus polar bears, may eventually disappear as they are re-incorporated into the grizzly population.
The author, Jessa Gamble, thinks this is a glimpse of things to come.