According to mammalogists in Nature, loss of Arctic sea ice could lead to the hybridization of certain marine mammals.
Well, okay, not really. But holy crap would that be awesome. The animals that are actually in danger of hybridizing include several seal species, e.g. ribbon seals with harp seals; narwhals with belugas; and right whales with bowhead whales.
This is especially bad news for right whales, as the North Polar sub-population consists of fewer than 200 individuals. With sea ice diminishing, the barriers that separates right whales from bowheads will eventually vanish – potentially leading to the mixing and sublimation of the genes that make right whales unique. These unique genes are precisely adapted to the North Polar sub-population’s niche, and if they’re diluted the population may suffer a serious decline in fitness.
Genetic diversity is what allows species to adapt and survive during periods of rapid and extreme change – like, say, the melting of all the sea ice. When genetically distinct populations interbreed, oftentimes the resultant chimera is less fit than its parents, and the entire gene pool grows more homogeneous, reducing adaptive potential. And, although whales haven’t yet begun to interbreed (the paper is merely speculative), polar and grizzly bears have, perhaps as a consequence of range shifts caused by climate change. Yikes.
On the other hand, mingling sub-populations isn’t always bad news. In fact, the study of island biogeography suggests that small, isolated populations are at greater risk of being wiped out by random fluctuations or freak tragedy (disease, famine, etc.). The elimination of sea ice barriers might therefore help sub-populations like the North Polar right whales, by providing them an important influx of new individuals to safeguard against sudden population crashes. And it’s possible that those bowhead whales possess some useful genes, too, that will actually bolster the right whales’ fitness.
There’s something psuedo-eugenic about rejecting hybridization in all cases, considering that many contemporary species are the byproducts of commingling. Species aren’t static; in fact, preventing hybridization may stifle evolution. The goal of conservation should be to maintain populations’ evolutionary potential, not to keep them preserved in glass.
Still, adaptive radiation – the evolution of species to fill every available niche – is what makes ecosystems resilient and productive, and hybridization negates adaptive radiation and its benefits. Environmental managers shouldn’t necessarily stamp out every hybrid, but have to consider culling ones that are the products of anthropogenic changes. In the case of salmon, for example, farmed fish have been escaping and mating with wild fish for many years, and there’s evidence that wild salmon are losing their migratory skills as a result.
All of that said, I think it’s pretty clear that a killer whalerus would dramatically enhance both species’ fitness, and oh by the way be totally effing awesome.