The tasty Heliconius numata butterfly evades predators by copying the wing patterns of foul-tasting Melinaea butterflies. H. numata, also known as the passion-vine butterfly, has to get the pattern exactly right or a sharp-eyed bird will spot the fake and gobble it up.
Born mimics, members of the species lock in wing patterns with flipped-around bits of DNA, Richard ffrench-Constant of the University of Exeter in England and colleagues report online August 14 in Nature.
The flipped DNA causes six or more genes — on a section of a chromosome important in setting wing patterns in butterflies and peppered moths — to be inherited as a single unit, a supergene. Different versions of the supergene allow H. numata to adopt seven different wing patterns reminiscent of several bad-tasting species.
Other Heliconius butterflies mimic only one nonpalatable species. Researchers aren’t sure if other butterfly species use DNA flipping to determine their patterns.