A species of butterflies, Heliconius numata, wards off potential predators by mimicking the wing patterns of other, less appetizing butterfly species. Interestingly, H. numata can display seven different precise wing patterns that have been selected and maintained through evolution, each replicating the exact appearance of a different type of butterfly. How such complex and detailed wing patterns are passed down genetically without variation has been an evolutionary mystery.
A team led by Lise Frezal (Muséum National d'Histoire Naturelle, Paris, France) and Robert T. Jones (University of Exeter, Cornwall, UK) has now uncovered how the trait is passed from generation to generation. They discovered that the wing pattern trait is conserved in a 'supergene,' a collection of genes located close together on a chromosome that are likely to be inherited together (Nature doi:10.1038/nature10341; published online 14 August 2011). Through the suppression of recombination, or the swapping of genes, at this site on the genome, each pattern arrangement is 'locked together.' This allows the collection of genes encoding the wing pattern trait to be passed on intact to the next generation. The findings of this study help to explain how multiple forms of a complex trait can be maintained within a population in order to provide an evolutionary advantage.
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