Global warming is redirecting ladybug evolution

There's a famous story about British moths during the Industrial Revolution, who in just a few short generations adapted to their soot-filled environment by evolving a matching black color. And now we've found the global warming equivalent: Dutch ladybugs.

The moths found around Liverpool in 19th century Britain faced extraordinary pressure from natural selection. Their colors had evolved so that they could camouflage themselves in their natural surroundings, but the rise of factories and mechanization had completely changed the landscape, choking the area with black soot. A rare mutation that made the moths black suddenly became the golden ticket to escape the watchful eye of predators, and in short order black moths had become the dominant form of the population.

Something similar appears to be going on today in the Netherlands. Previously, ladybugs there tended to come in two basic forms. Near the coast, two-spot ladybugs tended to be red with black spots. Further inland, they were more likely to be black with red spots. But over the last thirty years, that's started to shift, with more and more red bugs found inland, further away from their natural habitat on the coast.

The change has been a fairly dramatic one. In 1980, the red bugs with black spots, known as nonmelanic ladybugs, constituted 90% of coastal ladybugs and just 60% of those inland, with the black bugs with red spots, or melanic ladybugs, making up the remaining 10% and 40%. But in a recent sample, Cambridge ecological geneticist Paul Brakefield says he and his team couldn't find any area where melanic bugs made up more than 20% of the population.

The most likely culprit here is climate change. It's thought that the two types of ladybugs originally evolved to deal more effectively with climate, as the nonmelanic bugs could stay cooler on the warm coasts while the melanic bugs needed to be darker in order to survive in the colder inland regions. But the Netherlands, like much of the world, has seen consistent warming over the last few decades, and that's likely driven this shift to redder ladybugs.

The link appears strong, but it would require further work in the laboratory to demonstrate that the ladybugs can in fact shift colors over generations. Unfortunately, Brakefield says he can't continue to do field studies, due to another unexpected factors - an invasive species, the Japanese harlequin ladybug, escaped from a Belgian greenhouse and has now thoroughly outcompeted the native two-spotted ladybugs, driving their numbers way down to the point that they're now nearly impossible to find.

Via Science. Image by followtheseinstructions on Flickr.