Evolution of sexual dimorphism

在所有雌雄分开的动植物物种中，雄性和雌性在形态上，有时甚至在行为上都是不同的。我们知道，这些差异之所以产生，是因为两性在繁殖中扮演着不同的角色，因此面临着不同的选择压力。我们还不明白的是，男性和女性在选择上的差异究竟是如何导致两性之间的表型差异的。本项目解决了这个问题。在果蝇种群中，不同的选择压力如何导致对一种性别有利但对另一种性别有害的等位基因的积累，以及这种积累如何与性别之间选择差异的程度相关。此外，本研究旨在研究二态性的进化，通过对目前单态性状的不同人工选择创造一种新的二态性。这种方法将使人们了解种群对雄性和雌性的不同选择的反应速度和程度，以及这种反应在基因组中的位置（在性染色体X上与常染色体上）。此外，该实验将揭示两性之间的表型差异是如何在雄性和雌性的基因表达水平上受到调节的，以及哪些因素影响这种调节对选择的反应能力。综合起来，这些方法有可能阐明导致自然界中普遍存在的现象的进化步骤，并为其背后的分子过程提供见解。

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.