Friday, July 13, 2007

Evolution in action

But nobody can witness evolution! Except, y'know, when we can:
A population of butterflies has evolved in a flash on a South Pacific island to fend off a deadly parasite.

The proportion of male Blue Moon butterflies dropped to a precarious 1 percent as the parasite targeted males. Then, within the span of a mere 10 generations, the males evolved an immunity that allowed their population share to soar to nearly 40 percent — all in less than a year.

"We usually think of natural selection as acting slowly, over hundreds or thousands of years," said study team member Gregory Hurst, an evolutionary geneticist at the University College London. "But the example in this study happened in a blink of the eye, in terms of evolutionary time."

The scientists think the males developed genes that hold a male-killing microbial parasite, called Wolbachia, at bay.


The team ran genetic analyses to see if the parasite had somehow vanished. It hadn't. Wolbachia was still present in butterflies from both islands. Other lab experiments indicated the males had evolved suppressor genes to shield against the parasite.


"The suppressor gene allows infected females to produce males," Charlat said. "These males will mate with many, many females, and the suppressor gene will therefore be in more and more individuals over generations."

P.Z. has some more, including a reference to Y: The Last Man. Of course, P.Z.'s complaint is silly--Yorick did sire a baby!

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