Adaptation to desiccation resistance fails to generate pre- and postmating isolation in Drosophila melanogaster

Abstract

Many laboratory speciation experiments have raised allopatric populations in different environments to determine whether reproductive isolation evolves as a by-product of adaptation. Few, however, have controlled for the effects of genetic drift, addressed the evolution of both pre- and postmating isolation, or investigated the conditions that promote or hamper the process. I present results of a long-term evolution experiment in which 12 replicate populations of Drosophila melanogaster independently evolved for more than 57 generations under alternative desiccation treatments (six control and six desiccation-selected populations). Specifically, I demonstrate the divergence between the desiccation and control populations of cuticular hydrocarbons, key traits that have been implicated in mate choice and sexual isolation in Drosophila. Despite this divergence, there was no detectable pre- or postmating isolation between the desiccation and control populations. Novel environments are generally thought to promote the evolution of reproductive isolation. Understanding the conditions that favour or hamper this remains a key challenge for speciation research.