The Y chromosomes of Drosophila simulans are highly polymorphic for their ability to suppress sex-ratio drive.
The sex-ratio trait, known in several species of Drosophila including D. simulans, results from meiotic drive of the X chromosome against the Y. Males that carry a sex-ratio X chromosome produce strongly female-biased progeny. In D. simulans, drive suppressors have evolved on the Y chromosome and on the autosomes. Both the frequency of sex-ratio X and the strength of the total drive suppression (Y-linked and autosomal) vary widely among geographic populations of this worldwide species. We have investigated the pattern of Y-linked drive suppression in six natural populations representative of this variability. Y-linked suppressors were found to be a regular component of the suppression, with large differences between populations in the mean level of suppression. These variations did not correspond to differences in frequency of discrete types of Y chromosomes, but to a more or less wide continuum of phenotypes, from nonsuppressor to partial or total suppressor. We concluded that a large diversity of Y-linked suppressor alleles exists in D. simulans and that some populations are highly polymorphic. Our results support the hypothesis that a Y-chromosome polymorphism can be easily maintained by a balance between meiotic drive and the cost of drive suppression.
Montchamp-Moreau
C
C
Populations, Génétique et Evolution, CNRS, Gif-sur-Yvette, France. montchamp@pge.cnrs-gif.fr
Ginhoux
V
V
Atlan
A
A
D000818:Animals; D004330:Drosophila / Q000235:genetics* / Q000502:physiology; D005260:Female; D008297:Male; D008540:Meiosis / Q000235:genetics; D011110:Polymorphism, Genetic / Q000235:genetics; D012744:Sex Ratio; D018709:Statistics, Nonparametric; D014960:X Chromosome / Q000235:genetics / Q000502:physiology; D014998:Y Chromosome / Q000235:genetics* / Q000502:physiology