A postgenomic approach to the role of odour and gustatory receptors in speciation

All animals rely on sensing volatile and non-volatile chemicals in their environment (odour and gustatory senses, respectively). They use this information for detecting food, avoiding predators, finding mates and other crucial functions. The chemical senses are unlike other senses in that they require specific receptors for each compound or class of compounds to which they respond. Recently, in large part through genome sequencing projects, classes of genes coding for odorant and gustatory receptors have been identified and their characterisation is now proceeding rapidly. They may well be the key to understanding the recognition and processing of chemical information in many contexts. Odour and gustatory signals have central roles in speciation in many animals through their functions in both habitat and mate choice, arguably the two primary forms of premating reproductive isolation. The identification of odorant and gustatory receptor gene classes thus provides an exciting opportunity to take a systematic approach to the genetic basis of this key component of the speciation process. In this project, we will use genomic information and species of the Drosophila melanogaster subgroup to survey selectant odorant and gustatory receptor loci for variation within and between species. We will compare sequence divergence between species with levels of variation within species to detect loci that have evolved rapidly under natural selection. We will test for associations between odorant and gustatory receptor loci and key behavioural traits, such as mate and habitat choice, in recombinant inbred lines of crosses between species. This will confirm the roles of candidate loci in critical behavioural steps. We will examine gene expression in the same set of strains to test for loci that have altered expression patterns and so potentially novel functions. This will provide a systematic answer to the longstanding question of the relative roles of structural and expression modifications in adaptive evolution as well as pointing to candidate 'speciation genes'. The project is a collaboration between three laboratories with complementary expertise in this area. As well as the unparalleled insight into the genetics of speciation, the project will provide new data on the evolution of these fascinating and important genes with implications for their study in many other species and contexts including pest and disease vector control.