Divergence of larval morphology between Drosophila sechellia and its sibling species caused by cis-regulatory evolution of ovo/shaven-baby

We report an extreme morphological difference between Drosophila sechellia and related species of the pattern of hairs on first-instar larvae. On the dorsum of most species, the posterior region of the anterior compartment of most segments is covered by a carpet of fine hairs. In D. sechellia, these hairs have been lost and replaced with naked cuticle. Genetic mapping expe riments and interspecific complementation tests indicate that this differen ce is caused, in its entirety, by evolution at the ovo/shaven-baby locus. T he pattern of expression of the ovo/shaven-baby transcript is correlated wi th this morphological change. The altered dorsal cuticle pattern is probabl y caused by evolution of the cis-regulatory region of ovo/shaven-baby in th e D. sechellia lineage.