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Sunday, 25 March 2012





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Researchers solve Darwin’s copycat evolution puzzle

24 Mar,BBC

It is a clever trick if you can pull it off - mimic another, more dangerous animal and so avoid being eaten.Many insects try it, but it has been a long standing puzzle why some of the worst mimics in Nature can still seem to escape becoming a meal.Now, Canadian scientists tell Nature journal they can answer that one.Larger animals, they say, make for more substantial meals, and so their mimicry needs to be spot on. For small prey, a great performance is not so essential.

"Mimicry of harmless species pretending to be dangerous ones in order to avoid being eaten is one of the best celebrated examples of the outcome of evolution by natural selection," says Professor Tom Sherratt, of Carleton University in Ottawa, who led the research."Good examples of mimicry are highlighted in biology text books, but many mimics are poor and their emergence remains something of a puzzle."Mimicry is common among plants and animals.

Species of snakes, spiders and butterflies have all evolved to look like other species to ward off predators. But one of the great mysteries in biology is that most of this copy-cat behaviour is not very good, and bad impersonators seem just as abundant as the good ones.A simplistic interpretation of Darwin's theory of natural selection would suggest that it would be better for all mimics to closely resemble the species they are trying to impersonate.

One explanation for why some might not achieve this is the eye of the beholder theory.

This states that although the mimicking species aren't convincing to humans, they do fool their predators whose senses are quite different to ours.

Listen to the sound of a wasp followed by a hoverfly trying to sound like a wasp.Darwinian selection would suggest that over time the hoverflies that sounded most like wasps would be preferentially selected until a species emerged that sounded very nearly, if not exactly, like the creature it was trying to impersonate.

In contrast, the species that were poor mimics would all be eaten and die out. The new Canadian research suggests why this hasn't happened?Another theory is that poor mimics are an amalgamation of unappetising species and so, although they don't resemble any one of them to a predator, they do represent the worst possible combination.



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