The sex-ratio trait in Drosophila simulans: genetic analysis of distortion and suppression.

The sex-ratio trait described in several Drosophila species is a type of naturally occurring X-linked meiotic drive that causes males bearing a sex-ratio X chromosome to produce progenies with a large excess of females. We have previously reported the occurrence of sex-ratio X chromosomes in Drosophila simulans. In this species, because of the co-occurrence of drive suppressors, the natural populations and the derived laboratory strains show an equal sex-ratio even when sex-ratio X chromosomes are present at a high frequency. The presence of sex-ratio X chromosomes is established via crosses with a standard strain that is devoid of drive suppressors. In this article, we show first that the sex-ratio trait in D. simulans results from the action of several X-linked loci. Second we describe drive suppressors on each major autosome as well as on the Y chromosome. The Y-linked factors suppress the drive partially whereas the autosomal suppression can be complete.