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A team of European scientists has solved the mystery of how a butterfly changes its wing patterns to mimic neighbouring species and avoid being eaten by birds.
The study focussed on the Amazonian species Heliconius numata, which mimics several other butterfly species at a single site in the rainforest, to protect itself against predators. One population of Heliconius numata can, therefore, feature many distinct wing colour patterns resembling those of other butterflies, such as the Monarch’s relatives Melinaea, which are unpalatable to birds. The researchers located and sequenced the chromosomal region responsible for the wing patterns in H. numata. A single region on a single chromosome, containing several genes, which control the different elements of the pattern, controls the butterfly's wing-pattern variation. Known as a "supergene", this clustering allows genetic combinations that are favoured for their mimetic resemblance to be maintained, while preventing combinations that produce non-mimetic patterns from arising. Supergenes are responsible for a wide range of what we see in nature: from the shape of primrose flowers to the colour and pattern of snail shells. The researchers found that three versions of the same chromosome coexist in this species, each version controlling distinct wing-pattern forms. This has resulted in butterflies that look completely different from one another, despite having the same DNA. "We were blown away by what we found," said Dr Mathieu Joron of the Museum National d’Histoire Naturelle, who led the research. "These butterflies are the ‘transformers’ of the insect world. But instead of being able to turn from a car into a robot with the flick of switch, a single genetic switch allows these insects to morph into several different mimetic forms — it is amazing and the stuff of science fiction. "Now we are starting to understand how this switch can have such a pervasive effect," he stated. This single supergene also appears important in melanism in other species, including moths. "This supergene region not only allows insects to mimic each other, as in Heliconius, but also to mimic the soot blackened background of the industrial revolution — it’s a gene that really packs an evolutionary punch," Professor Richard ffrench-Constant of the University of Exeter added. The study has been published in the journal Nature. — ANI
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For the first time,
researchers led by the CNRS (Museum National d'Histoire Naturelle,
Paris) and the University of Exeter (UK) have shown how butterflies
perform this amazing trick, known as "Mullerian mimicry".