Male bias sex ratio drosophila

Modification of offspring sex ratios in response to parental quality is predicted when the long-term fitness returns of sons and daughters differ. One factor that may influence a mother's sex allocation decision is the quality or attractiveness of her mate. We investigated whether the sex ratios of offspring produced by female Drosophila melanogaster are biased with respect to the age of the males to which they are mated, and whether there is an adaptive basis for this phenomenon. This pattern does not appear to be due to a systematic difference in the numbers or mortality of the X- and Y-bearing sperm originating from old and young fathers, as the overall sex ratios of all offspring produced from a single copulation did not differ between broods fathered by the two types of males. The sons of older males fared worse in competitive mating assays than did the sons of younger males, while daughters of old and young males were of comparable fitness. These results suggest that there is an adaptive basis for the observed sex ratio modification.
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Operational sex ratios and sperm limitation in populations of Drosophila pachea | SpringerLink

Males have evolved a variety of behavioral, morphological, and physiological traits to manipulate their mates in order to maximize their chances of success. A common consequence of aggressive male mating strategies in Drosophila melanogaster is the reduction of female lifespan. Our study shows that this is common across members of the simulans clade. Reduced life expectancy of females implies that female contribution to a population is less than that of males per generation.
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Metrics details. One proposed consequence of inbreeding is a skewed sex ratio arising from sex specific mortality in the homogametic sex caused by inbreeding on the sex chromosome. However, recent work suggests that random distortions in sex ratio due to autosomal inbreeding may be of greater importance.
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Males of the cactophilic fruitfly, Drosophila pachea , produce relatively few but very large sperm, and partition their limited gamete numbers among successive mates. The present study found that males take 10 days longer than females, post-eclosion, to become sexually mature. The pattern of testes development suggests that the need to produce testes long enough to manufacture the giant sperm is the cause of the delayed male maturity. These findings generate the prediction that the operational sex ratio OSR of populations will be female-biased. The size, sex ratio, and OSR of natural populations were examined.
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