An international collaborative study to map the genome of a South American butterfly has identified the secret behind its mimetic nature.
These butterflies, in order to better survive in the wild, have taken successful survival techniques from other butterflies and have incorporated them into their own genetic code."—Dr Chris Jiggins of the University of Cambridge
The genome sequence of the Postman butterfly, Heliconius melpomene, was used as a reference to study species that live together in the Peruvian Amazon. Several of these share bright wing patterns in order to reinforce a warning signal that they are bad to eat – dissuading predators from attack.
Sequence data showed that those species with similar wing patterns shared a similar genetic signal, precisely in those narrow regions of the genome responsible for controlling patterns.† This is a result of hybrid exchange of genes between three co-mimic species, which has allowed them to copy each other’s wing patterns.
Chris Jiggins of the University of Cambridge said, "These butterflies, in order to better survive in the wild, have taken successful survival techniques from other butterflies and have incorporated them into their own genetic code. This is significant as it has occurred in a natural adaptive radiation, suggesting an important role for hybrids in the origins of biodiversity."
The phenomenon, known as adaptive introgression, involves different species sharing genetic material and has been considered very rare, especially in animals. Although many species can interbreed in the wild, the resulting hybrids are often infertile and considered an evolutionary dead-end.† However, occasionally hybrids might introduce useful genetic material that can help populations adapt to changing conditions.† This source of novelty might be more effective than having to wait for a mutation to occur in order to yield a similar result. In the case of butterflies, the effects can be clearly seen on their wings.
Kanchon Dasmahapatra, who worked with Professor James Mallet at University College London added, "What we show is that one butterfly species can gain its protective colour pattern genes ready-made from a different species by hybridizing (or interbreeding) with it. A much faster process than having to evolve one’s colour patterns from scratch."