'The Heliconius, or passion vine, butterflies are a colourful group of butterflies found in the rainforests of south and central America. Their bright wing colours act as warnings, telling predators that they are poisonous or unpleasant to eat because of toxic compounds they produce and get from the plants they eat (the passion vines).
Different species in this group often share the same colours and patterns, and this benefits both species by making it easier for the predators to learn to avoid the pattern.
Heliconius erato and Heliconius melpomene are not closely related and genetically very different, but have almost identical wing colour patterns. Another incredible thing about these two species is that in different parts of South
America they have evolved different wing colours and patterns. We have identified one of the genes that has changed between the different populations in South America to produce the differences in wing patterns, a gene called Cortex.

Amazingly, changes in Cortex were also responsible for producing black peppered moths, which spread during theindustrial revolution in England, when they were better able to hide against the soot-covered trees. These results are helping us to understand why particular genes, like Cortex, seem to be particularly good at producing the variation needed for evolution to happen.'