Tinker where the tinkering's good.

Do general principles govern the genetic causes of phenotypic evolution? One promising idea is that mutations in cis-regulatory regions play a predominant role in phenotypic evolution because they can alter gene activity without causing pleiotropic effects. Recent evidence that revealed the genetic basis of pigmentation pattern evolution in Drosophila santomea supports this notion. Multiple mutations that disrupt an abdominal enhancer of the pleiotropic gene tan partly explain the reduced pigmentation observed in this species.