Scientists have found a "supergene" that paints the stripes, spots and rays on a surprisingly diverse range of butterflies.
Butterfly wings provide an opportunity for scientists to understand how nature creates patterns and reveal how new species evolve, such as the non-poisonous butterflies that mimic the wings of poisonous types that birds avoid.
A genetic study of a range of South American butterflies, published yesterday in the journal PLoS Biology, has found that the same molecular pattern-forming machinery is at work in three different species of Heliconius butterflies: Heliconius melpomene and Heliconius erato, which look the same, and Heliconius numata, which looks different.
Dr Mathieu Joron, Dr Chris Jiggins, and colleagues at Edinburgh University studied the three species, two of whom mimic each other, and the third which copies the black, orange and yellow on the wings of a different species within another butterfly genus, Melinaea.
To find out how patterns are controlled, the team crossed differently patterned "races" of each species - those with the same patterned wings - and traced the source of the variation to the same spot on the insects' genetic codes, a "supergene" region responsible for producing wing pattern diversity in Heliconius butterflies.
The region allows the insects to evolve patterns in response to circumstances – for instance to mimic the warning patterns on another species of butterfly to boost survival.
In earlier work, the team created Heliconius heurippa after just three generations of breeding in a laboratory between two related species - Heliconius melpomene and Heliconius cydno. In this way, they hope to show how new species evolve.
The research confirms that surprisingly few genes control most of the dramatic colour pattern differences between butterflies. It will have implications for understanding other patterns that form in nature too, such as the development of the human embryo.