EVOLUTION OF DRIVING X CHROMOSOMES AND RESISTANCE FACTORS IN EXPERIMENTAL POPULATIONS OFDROSOPHILA SIMULANS

Abstract

Abstract.-Sex-ratio drive is a particular case of meiotic drive, described in several Drosophila species, that causes males bearing driving X chromosome to produce a large excess of females in their progeny. In Drosophila simulans, driving X chromosomes and resistance factors located on the Y chromosome and on the autosomes have been previously reported. In this paper, we report the study of the dynamics of sex-ratio factors in experimental populations. We followed the evolution in frequency of driving X chromosomes in the absence of resistance factors and the evolution of resistance factors in the presence of driving X chromosomes. The driving X chromosome was lost, contrarily to theoretical expectations that predict its rapid invasion. Autosomal resistances increased in frequency, and resistant Y chromosomes invaded the population very quickly, as predicted by theoretical models. Fitness measurements showed that the loss of the driving X chromosome was due to a strong deleterious effect that was expressed only when distorting males were in competition with standard males. However, the spread of autosomal resistances reduced this deleterious effect. Implications for the maintenance of polymorphism in natural populations are discussed.

Selfish genetic elements and sexual selection: their impact on male fertility

“…The second potential source of bias is the preferential reporting of studies that found a particular relationship. However, four of the papers included only report fertility as a secondary point and did not mention it in the abstract (Hartl et al 1967;Capillon and Atlan 1999;Tao et al 2001;Orr and Irving 2005). In two further papers, fertility was not a major focus of the paper (Wood and Newton 1991;Beckenbach 1996), and in two others a large number of male traits were examined in which fertility was included (Beukeboom 1994;Snook et al 2000).…”

“…Studies that report no difference in fertility between SR and standard males are either a large scale population cage experiment (Capillon and Atlan 1999) or a field study (Beckenbach 1996), which estimate fertility effects from overall population results, whereas those demonstrating differences are detailed studies of individual flies (Wu 1983a;Atlan et al 2004). Clearly the methodology used can have significant impacts on the results, suggesting that the fertility differences are only revealed in circumstances that allow multiple mating.…”

Sex Chromosome Drive

“…In the Middle Eastern populations, suppression seems to be increasing much more quickly in one population than in the other, possibly reflecting Y-linked resistance as opposed to autosomal suppression dynamics. In both species, the increase in suppression in response to SR fixation had been shown in experimental populations (Carvalho et al 1998;Capillon and Atlan 1999).…”

The Y Chromosomes of Drosophila Simulans Are Highly Polymorphic for Their Ability to Suppress Sex-Ratio Drive

“…Such a frequency-dependent mechanism is possibly widespread because sex-ratio X chromosomes are known in several species to reduce male fertility when mating occurs repeatedly (Wu 1983a;Jaenike 1996). Density-dependent deleterious effects, related to sexual competition between males, were also invoked to explain the elimination of sex-ratio X from experimental populations of D. simulans (Capillon and Atlan 1999).…”