Butterfly Study Sheds Light On Convergent Evolution: Single Gene Controls Mimicry Across Different Species (http://www.sciencedaily.com/releases/2011/07/110721142416.htm)
QuoteScienceDaily (July 22, 2011) — For 150 years scientists have been trying to explain convergent evolution. One of the best-known examples of this is how poisonous butterflies from different species evolve to mimic each other's color patterns -- in effect joining forces to warn predators, "Don't eat us," while spreading the cost of this lesson.
..."This is our first peek into how mimicry and convergent evolution happen at a genetic level," Reed said. "We discovered that the same gene controls the evolution of red color patterns across remotely related butterflies...
An interesting insight into the effects of mutations. If a limited number of genes control significant characteristics then small mutations can have large selective effects.