The Postman butterfly, a brightly colored favorite of collectors and scientists since its discovery in the Victorian era, tastes bad -- very bad. Predators who have bitten into one shy away from future contact because of the foul aftertaste. The butterflies have taken advantage of this trait by developing distinctive black and red wing coloration that quickly warns predators to stay away.
An international collaboration of scientists has now sequenced the genome of the Postman butterfly -- more formally known as Heliconius melpomene -- and shown that this unusual coloring has been passed among related species by hybridization, a crossbreeding among species that is rarely found in the wild because it usually makes the offspring less likely to survive. The coloring is then retained in the other species by a phenomenon known as introgression, in which the hybrid breeds with a parent species, transferring the crucial genes.
Heliconius, with 43 species and hundreds of races, is a widely studied insect because it is very useful for studying adaptive radiation and development of new species. Caterpillars of H. melpomene feast on passion fruit vines in the Peruvian Amazon.
To learn more about the species, a collaboration of more than 70 researchers at nine institutions around the world decided to sequence its genome -- the long coil of DNA that serves as the blueprint for the butterfly. The growing availability of low-cost sequencing techniques made it possible for the group, called the Heliconius Genome Consortium, to fund the research by diverting small amounts of money from their other grants. Their results were published Thursday in the journal Nature.