April 6, 2009

Study solves butterfly wing eyespot puzzle

Yale University biologists say they've determined butterflies seem able to both attract mates and ward off predators by using different sides of their wings.

You want to be noticeable and desirable for mates, but other onlookers, including predators, are paying attention to those signals as well, said Jeffrey Oliver, a Yale postdoctoral researcher.

Oliver was interested in whether the eyespots on the upper side of butterflies' wings serve a different purpose than the ones on the underside. Ever since Darwin's time, biologists, including Darwin himself, have postulated whether the upper patterns could be used to attract mates, while at the same time, those on the underside could help avoid predators.

Working with Yale biologist Ant³nia Monteiro and Kendra Robertson of the State University of New York-Buffalo, Oliver found eyespots on the upper side of the wings appear to evolve much more quickly than those on the underside, meaning they appear and disappear frequently through the course of evolution. The result is consistent with the theory that they are used to attract mates, since signals used for sexual selection tend to evolve faster than others.

Oliver said his study is the first to employ evolutionary history models to show a species can use the same signal on different areas of its body to communicate different messages.

The study appeared online in the Proceedings of the Royal Society B: Biological Sciences.