Evolution of sexual dimorphism

In all animal and plant species with separate sexes, males and females differ in their morphology and sometimes behaviour. We know that these differences have arisen because the sexes have different roles in reproduction and are therefore under different selection pressures. What we have not understood yet is how exactly the difference in selection between males and females leads the phenotypic divergence between the two sexes. The present project addresses this question. It proposes to investigate how divergent selection pressures lead to the accumulation of alleles that are beneficial to one sex but detrimental to the other, in populations of the fruitfly Drosophila melanogaster, and how this accumulation is related to the extent to which selection differs between the sexes. Further, it aims at studying the evolution of dimorphism by creating a novel dimorphism through divergent artificial selection on a presently monomorphic character in D. melanogaster. This approach will give insight in the rate and degree to which populations can respond to divergent selection on males and females and where this response is located in the genome (on the sex-chromosome X vs. the autosomes). Further, the experiment will reveal how the phenotypic divergence between the sexes is regulated at the level of the expression of genes in males and females and what factors affect the ability of this regulation to respond to selection. Taken together, these approaches have the potential to elucidate the evolutionary steps leading to a phenomenon that is ubiquitous in nature and give insights in the molecular processes that underlie it.