mirrordetermines the far posterior domain in butterfly wings

Insect wings, a key innovation that contributed to the explosive diversification of insects, are recognized for their remarkable variation and many splendid adaptations. Classical morphological work subdivides insect wings into several distinct domains along the antero-posterior (AP) axis, each of which can evolve relatively independently. There has been little molecular evidence, however, for AP subdivision beyond a single compartment boundary described fromDrosophila melanogaster. Here we show that the transcription factormirroracts as a selector gene to differentiate a far posterior domain in the butterfly wing, classically defined as the vannus, and has wide-ranging effects on wing shape, scale morphology, and color pattern. Our results confirm that insect wings can have more than one posterior developmental domain, and support models of how selector genes may facilitate evolutionarily individuation of distinct AP domains in insect wings. Our results also suggest that the alula, a smallmirror-dependent structure at the base of theD. melanogasterwing, may be an evolutionary derivative of the vannus, and therefore that theD. melanogasterwing blade is a solitary remigium that represents only a fraction of the archetypal insect wing.