CONSERVATION OF MOLECULAR PREPATTERNS DURING THE EVOLUTION OF CUTICLEMORPHOLOGY IN DROSOPHILA LARVAE

We are using patterns of cuticle specialization in Drosophila larvae a s models to investigate the molecular, genetic, and developmental base s of morphological evolution. Members of the virilis species group dif fer markedly from one another in the distribution of hairs on the dors al surface of first instar larvae. In particular, characteristic bands of hairs cover about 20% of each trunk segment in some species but ab out 70% in others. These major types do not correlate with recently pr oposed phylogenetic relationships, suggesting that similar phenotypes have arisen independently in different lineages. The patterns of expre ssion of several genes that control or reflect intrasegmental patterni ng are indistinguishable in species with very different cuticle morpho logies. We conclude that, in this case, morphology probably has evolve d via altered response to a conserved molecular prepattern.