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Abstract

Sex-ratio drive, which results in males siring female-biased progeny, has been reported in several Drosophila species, including D. simulans. It is caused by X-linked drivers that prevent the production of Y-bearing sperm. In natural populations of D. simulans, the drivers are usually cryptic, because their spread has elicited the evolution of drive suppressors. We investigated autosomal suppression in flies from Madagascar, Réunion and Kenya. Autosomal suppressors were found in all three places, indicating that they are a regular component of drive suppression over this geographic area, where strong Y-linked suppressors also occur. These suppressors were suspected of being polymorphic in Madagascar and Réunion and proved to be polymorphic in Kenya. We developed a model simulating the evolution of neutral autosomal suppressors in order to explore the effects of the number of suppressor genes, their relative strength and the co-occurrence of Y-linked suppressors. The most interesting prediction of the model is that when suppression is multigenic, suppressor loci can remain polymorphic despite the absence of balancing selection if an equal sex-ratio is restored in the population before the suppressor alleles become fixed at all loci. The model also emphasises the importance of the sterility of distorters' sons in suppressor dynamics.

Sequence Analysis of the Segmental Duplication Responsible for ParisSex-RatioDrive inDrosophila simulans

“…This kind of duplication is probably deleterious most of the time and, thus, destined to disappear quickly. In the present case, the duplication has a strong, negative effect on male fertility that is a direct consequence of drive (Angelard et al 2008; Atlan et al 2003; Atlan et al 2004) and should cause many other perturbations via overexpression of the six duplicated genes or rIST and Hosim1-SR activity. In this respect, meiotic drive can be understood as a process that allows genetic rearrangements, such as duplications or inversions, to be maintained in the genome in spite of associated deleterious effects, as first proposed by Hedrick (1981).…”

The role of meiotic drive in hybrid male sterility

“…Autosomal suppressors will adjust the SR back to normal; however, they may not spread to fixation quickly. Y-linked suppressors can also restore the SR and will exhibit intense positive selection as non-suppressing Y chromosomes will not appear (Hurst & Pomiankowski 1991;Atlan et al 2003). However, the size, gene content and number of autosomes compared with the Y chromosome provide greater possibility for suppressors to evolve (Hurst & Pomiankowski 1991).…”

“…However, the size, gene content and number of autosomes compared with the Y chromosome provide greater possibility for suppressors to evolve (Hurst & Pomiankowski 1991). Atlan et al (2003) further showed that when the strength of autosomal suppression of drive was substantially greater than Y-linked suppression, autosomal suppressors would spread faster. This observation suggests a reason why autosomal suppressors are observed in so many drive systems and why drive systems that contain Y-linked suppressors nearly always contain autosomal suppressors as well (Stalker 1961;Carvalho & Klaczko 1993Jaenike 1999).…”

A sex-ratio Meiotic Drive System in Drosophila simulans. I: An Autosomal Suppressor

“…The Paris sex-ratio ( SR ) appears to have originated relatively recently, and evolutionary signatures of a recent selective sweep are evident [23]. Multiple suppressors on the autosomes and the Y chromosome have been reported [19,21,24]. Both the distorters and the suppressors are polymorphic across the worldwide distribution of D.…”