Local selection underlies the geographic distribution of sex-ratio drive in Drosophila neotestacea

“Selfish” genetic elements promote their own transmission to the next generation, often at a cost to the host individual. A sex-ratio driving X-chromosome prevents the maturation of Y-bearing sperm, and as a result is transmitted to 100% of the offspring, all of which are female. Because the spread of a sex-ratio chromosome can result in a female biased population sex ratio, the ecological and evolutionary consequences of harboring this selfish element can be severe. In this study, we show that the prevalence of sex-ratio drive in Drosophila neotestacea varies between 0-30% among populations, and is common in the south while rare in the north. The prevalence of sex-ratio is not associated with the presence of suppressors of drive, geographic distance, or genetic distance based on autosomal microsatellite loci. Instead, our results indicate that ecological selection on sex-ratio drive varies among populations, as the prevalence of sex-ratio is highly correlated with climatic factors, wit...