Journal of Heredity 2004:95(1)
© 2004 The American Genetic Association 95:35-45
Identification of Quantitative Trait Loci Affecting Sex Determination in the Eastern Treehole Mosquito (Ochlerotatus triseriatus)
From the Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523. Funding for this research was provided by National Institutes of Health grant ROl (AI)41041 (to W.C.B.) and by the Colorado State University College Research Council.
Address correspondence to William C. Black IV at the address above, or e-mail: wcb4{at}lamar.colostate.edu.
Laboratory colonies of the eastern treehole mosquito (Ochlerotatus triseriatus (Say)) exhibit a consistent female-biased sex ratio. This is unusual among mosquito species, in which heritable sex ratio distortion is usually male biased and mediated by meiotic drive. Quantitative trait loci (QTL) affecting sex were mapped in an F1 intercross to better understand the genetics underlying this female bias. In P1 and F1 parents and in 146 F2 individuals with a female-biased sex ratio (106 females:40 males), regions of seven cDNA loci were analyzed with single-strand conformation polymorphism (SSCP) analysis to identify and orient linkage groups. Genotypes were also scored at 73 random amplified polymorphic DNA (RAPD)-SSCP loci. In addition to the sex locus, at least four QTL affecting sex determination were detected with interval mapping on linkage groups I and II. Alleles at the sex locus cumulatively accounted for approximately 6177% of the genetic variance in sex. Alleles at QTL adjacent to the sex locus and at a QTL on the opposite end of linkage group I increased the proportion of females, but alleles at a QTL on linkage group I and a second QTL on linkage group II increased the proportion of males. The female-biased sex ratio observed in laboratory colonies of O. triseriatus is most easily explained by the existence of multiple female biased distorter loci, as have been observed in other Diptera.