Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene

Repeated evolution of the same morphological trait is quite common, prompting the question whether evolution is constrained to follow certain paths, or whether there are many genetic routes to a phenotype. A study of the male wing pigmentation pattern involved in Drosophila courtship display shows that similar patterns arose independently at least twice and were lost at least five times in related Drosophila species. All these events involved regulatory changes at the yellow pigmentation gene but the two independent gains of wing spots resulted from co-option of different regulatory elements. Evolution went through the gene twice, but took a different route each time.