Research by evolutionary ecologist Timothy Farkas ’08 MA ’10 on how the rapid evolution of stick insect camouflage can impact entire ecosystems was recently published by Current Biology, and further featured by Carl Zimmer in his blog ‘The Loom’ on National Geographic.
Timothy, who studied biology and environmental science at Wesleyan, was a BA/MA student under advisor Professor Mike Singer.
The color of an animal can determine whether it lives or dies. If it’s easily spotted by predators, it may well become a meal. Hidden nicely against its background, an animal can escape its enemies for another day.
If the walking sticks get on the wrong bush, however, they lose their disguise. Against the thin leaves, the solid green insects leap out. Against the big leaves, the pale stripe of the other walking sticks looks out of place.
Nosil and his colleagues have been studying how these different kinds of camouflage play out in the California hills. A map of the insects and the bushes bears out this idea. In places where there are lots of thick-leaves bushes, the walking sticks are mostly solid green. In places where the thin-leaved bushes dominate, most of the insects have a white stripe. But if a thick-leafed bush is surrounded by thin-leaved ones, it will have many mismatched insects. That’s a pattern you’d expect from the combination of bird-driven natural selection and insects moving among neighboring bushes.
To put this idea to a thorough test, Nosil, his student Tim Farkas, and their colleagues studied 186 bushes in the California hills. They caught every walking stick insect on the bushes to do a population census. They found that when the insects were well-matched to the bush, their numbers were high. When they were badly matched, the population was much lower. That pattern makes sense if the birds are picking off the insects that are standing out against the bushes.
Image: from Timothy E. Farkas
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