Heliconius numata is the Amazon rainforest's ultimate master of disguise. Despite sharing the same DNA, different H. numata can nevertheless masquerade as a range of bad-tasting butterflies to protect themselves from predation — an evolutionary trait that has scientists comparing these butterflies to everyone's favorite robots in disguise.
What's so amazing about H. Numata is that if you aren't looking carefully, a single population of the butterflies won't look like a population at all, but rather a group of several different butterfly species.
In scientific circles, this trick is known as "Müllerian mimicry." This mimicry is thought to help some species of butterflies stay alive by allowing them to take on the wing patterns of butterflies known to taste awful to predators like birds.
The evolutionary underpinnings of Müllerian mimicry have puzzled scientists for generations (mimicry was, in fact, one of the first observations to give rise to the concept of natural selection itself). But now, in a paper published in this week's issue of Nature, scientists have uncovered the answer to one of the oldest questions in the history of evolutionary biology.
In search of a genetic answer to the puzzle of Müllerian mimicry, Dr. Mathieu Joron of the Muséum National d'Histoire Naturelle led a team of researchers on a search of the chromosomal region responsible for wing pattern in H. Numata. What they found was a "supergene," a specific region on a single chromosome that contains several different genes that are all capable of controlling different elements of the wing pattern.
According to Joron, the researchers were blown away by the discovery:
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.
The researcher's findings serve as a powerful reminder that scientific progress is forever providing new ways to look at age-old problems. Speaking to this idea, professor Richard H. ffrench-Constant of the University of Exeter said:
This phenomenon has puzzled scientists for centuries — including Darwin himself...Now that we have the right tools we are able to understand the reason for this amazing transformation: by changing just one gene, the butterfly is able to fool its predators by mimicking a range of different butterflies.