Selfish genetic elements spread because they enhance their own transmission at the expense of organismal fitness. But what is their effect on populations fitness, do they enhance or resist extinction? In this project, we will build on a decade of theoretical and experimental work on X-linked meiotic drive. Drive males sire female-only broods (Y-bearing sperm are dysfunctional) leading to a female biased population sex ratio. This raises population birth rates and is predicted to resist the chances of extinction. But X-linked drivers are typically located in chromosomal inversions which accumulate deleterious mutations. And as drive spreads, males become rare, leading to reduced female mating, with predicted reduced fertility and promotion of extinction. So drive has both positive and negative effects on population fitness.
These ideas will be studied in the stalk-eyed fly which carries sex-ratio, an X-linked meiotic driver. This species is also a classic examples of sexual selection caused by strong female mate preferences for males with exaggerated eyespan. Population cage experiments will be used to test how the frequency of meiotic drive, the population sex ratio and the opportunity for mate choice contribute to population persistence. The hypotheses will be tested further using samples of wild populations from our field sites in Malaysia; data shows the frequency of X-drive varies considerably between populations and over time. We are assembling the genome of the stalk-eyed fly and will analyse genetic variation across the sex-ratio X chromosome to study evidence of mutation accumulation and adaptive selection.