ETo be or not to be eaten, that is the question. For many animals, the only valid specter is that of their predator. And as any dialogue with him turns out to be impossible, nature has offered the prey different strategies. Escape, of course, but you still have to have the time. Camouflage then disappears into the background. Or imitate an inedible element – a branch, a leaf, what biologists call the sweet name of masquerade. Other species rather choose mimicry: take on the appearance of another animal, dangerous, to repel predators. Moths pass for wasps, octopuses for sea snakes…
One of the most fascinating strategies is undoubtedly aposematism. Suggested by Alfred Wallace (1823-1913) to Charles Darwin (1809-1882) in their correspondence on the subject of caterpillars and hornets, it consists of a species having a toxic substance and indicating it as clearly as possible by displaying a signal to predators. Typically a bright color. Insects, mammals, reptiles, molluscs, amphibians: almost everywhere in the kingdom of life, this mode of defense has found followers.
For decades, however, it has posed an enigma to biologists: its appearance. For a signal to be profitable, it must have been preceded, in its evolution, by the presence of the toxic substance. Before this one appears, the best strategy therefore remains camouflage. So far, everyone is in agreement. But then, how does a cryptic species become aposematic? “ It seems a mysteryexplains Tom Sherratt, professor of biology at Carleton University in Ottawa (Canada). The first visible mutants of a cryptic species should be quickly detected by predators and not so easily recognized as poisonous. » Killed by mistake, in short, like Polonius by Hamlet, for lack of the predators having had the time to learn the warning role of the colored signal. So how did this property spread?
An intermediate stage
In an article published Friday, March 17 in the journal Science, Tom Sherratt’s team presents a scenario. The aposematic species would have gone through an intermediate stage in which they have strong but mostly hidden signals. Such species exist in nature: moths Catocala, with their cryptic forewings and vivid hindwings. Or different amphibians, which hide their bright colors on their bellies and only show them in case of danger.
You have 32.89% of this article left to read. The following is for subscribers only.