Molecular evolution of the sex peptide network in Drosophila

Successful reproduction depends on interactions between numerous proteins beyond those involved directly in gamete fusion.   While such reproductive proteins evolve in response to sexual selection pressures, how networks of interacting proteins arise and evolve as reproductive phenotypes change remains an open question.  Here, we investigated the molecular evolution of the “sex peptide network” of Drosophila melanogaster, a functionally well-characterized reproductive protein network.  In this species, the peptide hormone sex peptide (SP) and its interacting proteins cause major changes in female physiology and behavior after mating.  In contrast, females of more distantly related Drosophila species do not respond to SP.  In spite of these phenotypic differences, we detected orthologs of all network proteins across 22 diverse Drosophila species and found evidence that most orthologs likely function in reproduction throughout the genus.  Within SP-responsive species, we detected the recu...