After so many years in the public eye, skunks have lost their pizzazz. It’s not their fault, it’s just that we’ve all forgotten how bizarre they are. Very few animals can fire sulphurous fluids out of their bums to incapacitate their foes, after all. Very few. But good on skunks, really, for keeping it weird.
One particular variety, the western spotted skunk—which balances on its front legs before it sprays you, as if that’s a charming consolation—just got even weirder. In a study published today in the journal Ecology and Evolution, researchers report that the two-pound terror has evolved into three genetically distinct groups, called clades, in an intriguing way: not with geological isolation (the classical impetus for getting populations to diverge genetically) but with climatic isolation. That is, dramatic climate change led to a genetic splintering of the species.
It’s actually fairly easy to get a new species. Just run a river or a mountain range through a population, splitting it in two. In their isolation, the groups will eventually grow so genetically distinct that they can no longer mate and produce offspring. Boom, two new species. The spotted skunk is kind of up to the same thing, though it hasn’t diverged enough to become new species, but instead three clades: western (California, Nevada, Baja California), Arizona, and east-central (Texas and Mexico). Though the clades existed in different geographical areas, they weren’t necessarily cordoned off from each other by geological boundaries.
By melding climate models and genetic work that showed when the spotted skunk began diverging, the researchers determined that the three clades likely got stuck in isolated pockets of actually habitable habitat during the Pleistocene Ice Age. “The idea is that these suitable conditions would contract when glaciers were expanding—it was cooler periods—and then expand during the interglacial periods,” says mammalogist and study co-author Adam Ferguson of the Field Museum.
The spotted skunk’s divergence began about 1 million years ago, and continued as glaciers in North America expanded and contracted over millennia. “Unlike the anthropogenically induced climate change we are experiencing today, the change in temperatures and rainfall patterns was more gradual,” Ferguson says, “occurring over thousands to tens of thousands of years.” These fluctuations as the glaciers moved in and out probably created suitable wooded habitats for skunks, and destroyed others, as groups of the creatures evolved in isolation.
Really, it’s not hard to see how this could come about. Say a forested area started drying out, and grasslands took over for dying trees. “The western spotted skunks really depend on cover and thick areas for protection from aerial predators,” Ferguson says, “and so crossing these open grasslands might not have been possible for them per se.” Western America’s newfound plains were just as restrictive for the skunk as new rivers or mountain ranges would have been.
The beauty of it all is that scientists can use this data to get a better picture of a disorderly climatic future. “By projecting into the past and understanding what happened to this species, it could give us an idea of how changing climates of the future could potentially change at least the distribution of suitable areas for this species,” Ferguson says.
The spotted skunk’s evolutionary journey is also a reminder that climate change affects different creatures in different ways. Warming oceans are definitely bad for coral, for instance. But other species will adapt to a planet in flux, like the spotted skunk did during the Pleistocene.
Problem is, it’s not just human-made climate change that’s the issue, but human-made everything. Urban development in particular threatens mammals all over the world. “If there’s bigger freeways, and all these other things dividing up the land, it’s going to be harder for small populations to persist,” says ecologist Craig Benkman.
But here’s to the continued survival of the spotted skunk. I for one am glad it got its groove back.