Final Activity Report Summary - SEX RATIO AND EVOLUT (Consequences of strongly blased sex ratios for evolution and ecology)
Our work has shown that sex ratio distortion has a significant effect on host reproductive biology. Despite the relatively short duration of our experiment, we observed changes in both behaviour and reproductive morphology of the flies in response to sex ratio bias. These changes were found to increase the overall productivity of populations harbouring sex ratio distorters. This means that adaptation to a biased sex ratio tends to stabilise populations and reduce elevated extinction risk otherwise associated with sex ratio bias. Importantly, our results also showed that adaptation can be impeded by the increase of genetic drift associated with sex ratio bias. In population with a very uneven sex ratio, evolutionary change can be dominated by stochastic fluctuations in gene frequencies. In small populations or with extreme sex ratio bias, these random effects can outweigh directional evolutionary change and prevent a response to selection. Our experiments demonstrated that, in agreement with this theoretical expectation, adaptation to sex ratio bias requires a large population size.