Duplicity

Take a look at the two butterflies on the right. Identical, right? Well, not exactly. They're actually two separate species in the genus Heliconia. That's H. melpomene on the top and H. erato on the bottom. They're classic examples of what's known ecologists and evolutionary biologists refer to as Mullerian mimicry, the situation in which two untasty organisms come to resemble one another as a way of reinforcing their evolutionary lesson of unpalatability. The butterflies have long been a rich source of examples of mimicry, from the old story of the monarch and the viceroy (which has turned out not to be as simple as previously believed) to the many examples of mimicry demonstrated by the heliconids, commonly known as the passion-vine butterflies.

Such perfect mimicry has motivated researchers to understand the genetic mechanism by which its produced. Given the large size of the genome, it was considered likely that different genes had to be involved in producing the color patterns observed in the two butterfly species. As it turns out - not the case. Two papers in PLoS Genetics, one examining the population genetics of H. melpomene and another mirroring that work for H. erato, indicate that very small regions of the genomes of both butterflies are involved in determining the color pattern of the wings. Other genes, corresponding to those that affect color pattern of other butterflies, do not play a role in the mimicry.

The researchers now plan to turn their focus to the genetic control of behavior in these species, as preliminary results indicate that the same genes are involved.