The mystery of how a butterfly has changed its wing patterns to mimic neighbouring species and avoid being eaten by birds has been solved by a team of European scientists. The study is published today (14 August 2011) in the journal Nature.
The greatest evolutionary thinkers, including Wallace, Bates and Darwin, have all wondered how butterflies that taste bad to birds have evolved the same patterns of warning colouration. Now for the first time, researchers led by the CNRS (Musum National d'Histoire Naturelle, Paris) and the University of Exeter (UK) have shown how butterflies perform this amazing trick, known as 'Mllerian mimicry'.
Funded by the Biotechnology and Biological Sciences Research Council (BBSRC), the study focused on the Amazonian species Heliconius numata, which mimics several other butterfly species at a single site in the rainforest. One population of Heliconius numata can therefore feature many distinct wing colour patterns resembling those of other butterflies, such as the Monarch's relatives Melinaea, which are unpalatable to birds. This acts as a disguise, protecting them against predators.
The researchers located and sequenced the chromosomal region responsible for the wing patterns in H. numata. The butterfly's wing-pattern variation is controlled by a single region on a single chromosome, containing several genes which control the different elements of the pattern. Known as a 'supergene', this clustering allows genetic combinations that are favoured for their mimetic resemblance to be maintained, while preventing combinations that produce non-mimetic patterns from arising. Supergenes are responsible for a wide range of what we see in nature: from the shape of primrose flowers to the colour and pattern of snail shells.
The researchers found that three versions of the same chromosome coexist in this species, each version controlling distinct wing-pattern forms. This
|Contact: Sarah Hoyle|
University of Exeter