An X-linked sex ratio distorter in Drosophila simulans that kills or incapacitates both noncarrier sperm and sons.
Bottom Line: X-linked son-killers are predicted by theory to be favored by natural selection and evolve when brothers and sisters compete for shared limiting resources and/or when brothers reduce the inclusive fitness of their sisters via sib-mating-a phenomenon called SA-zygotic drive.Autosomal-dominant suppressors of Winters (Nmy) and Durham (Tmy) failed to suppress skew.A Y-linked suppressor of Paris, however, did suppress skew, and a recombination test failed to detect recombinants between these two sex ratio distorters, indicating that they are tightly linked and plausibly identical or allelic.
Affiliation: Department of Ecology, Evolution & Marine Biology, University of California, Santa Barbara, California 93106.Show MeSH
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Mentions: The three stages of the screen are depicted in Figure 1, Figure 2, and Figure 3 and all of the crosses used in the screen are summarized in Figure 4. The screen is designed to operate in a manner analogous to a dichotomous taxonomic key. At the top of Figure 1, an observed female-biased sex ratio is potentially due to X-linked SD, endosymbiont/mitochondrial-coded SK, X-linked SA-ZD, and/or nuclear viability factors that reduce male survival relative to female survival. As one proceeds down the binary decision key, any step to the left terminates the screen and leads to the conclusion that the available data are consistent with sex ratio distortion being caused by one or more factors that do not include SA-ZD. Navigating to the left does not unambiguously identify the true cause(s) of sex ratio distortion—it only demonstrates that there is insufficient evidence to conclude that SA-ZD is operating. If one navigates to the base of the key in Figure 4, then the step-wise process-of-elimination demonstrates that at least some of the observed sex ratio distortion in the line is due to SA-ZD. This screen will fail to detect SA-ZD (false negatives) when it is weak and/or when its suppressors are present in the control line with an even sex ratio, but it should not lead to false positives –as described more fully in the discussion section.
Affiliation: Department of Ecology, Evolution & Marine Biology, University of California, Santa Barbara, California 93106.