title: X chromosome drive in a widespread Palearctic woodland fly, Drosophila testacea.
abstract: Selfish genes that bias their own transmission during meiosis can spread rapidly in populations, even if they contribute negatively to the fitness of their host. Driving X chromosomes provide a clear example of this type of selfish propagation. These chromosomes have important evolutionary and ecological consequences, and can be found in a broad range of taxa including plants, mammals and insects. Here, we report a new case of X chromosome drive (X drive) in a widespread woodland fly, Drosophila testacea. We show that males carrying the driving X (SR males) sire 80-100% female offspring and possess a diagnostic X chromosome haplotype that is perfectly associated with the sex ratio distortion phenotype. We find that the majority of sons produced by SR males are sterile and appear to lack a Y chromosome, suggesting that meiotic defects involving the Y chromosome may underlie X drive in this species. Abnormalities in sperm cysts of SR males reflect that some spermatids are failing to develop properly, confirming that drive is acting during gametogenesis. By screening wild-caught flies using progeny sex ratios and a diagnostic marker, we demonstrate that the driving X is present in wild populations at a frequency of ~ 10% and that suppressors of drive are segregating in the same population. The testacea species group appears to be a hot spot for X drive, and D. testacea is a promising model to compare driving X chromosomes in closely related species, some of which may even be younger than the chromosomes themselves.
authors.affiliation: Department of Biology, University of Victoria, Victoria, BC, Canada.
authors.forename: G L
authors.identifier: 0000-0002-5567-7946
authors.initials: GL
authors.lastname: Keais
authors.affiliation: Department of Biology, University of Victoria, Victoria, BC, Canada.
authors.forename: M A
authors.initials: MA
authors.lastname: Hanson
authors.affiliation: Department of Biology, University of Victoria, Victoria, BC, Canada.
authors.forename: B E
authors.initials: BE
authors.lastname: Gowen
authors.affiliation: Department of Biology, University of Victoria, Victoria, BC, Canada.
authors.forename: S J
authors.initials: SJ
authors.lastname: Perlman
mesh_terms: D000818:Animals; D004330:Drosophila / Q000235:genetics*; D005260:Female; D065928:Forests; D000075423:Gene Drive Technology; D008297:Male; D008540:Meiosis; D012744:Sex Ratio; D014960:X Chromosome; D014998:Y Chromosome
keywords: Drosophila; X chromosome drive; genetic conflict; meiotic drive; segregation distortion; selfish genetic elements