An Evolutionary Cost of Separate Genders Revealed by Male-Limited Evolution

Abstract

Theory predicts that intralocus sexual conflict can constrain the evolution of sexual dimorphism, preventing each sex from independently maximizing its fitness. To test this idea, we limited genome-wide gene expression to males in four replicate Drosophila melanogaster populations, removing female-specific selection. Over 25 generations, male fitness increased markedly, as sexually dimorphic traits evolved in the male direction. When male-evolved genomes were expressed in females, their fitness displayed a nearly symmetrical decrease. These results suggest that intralocus conflict strongly limits sex-specific adaptation, promoting the maintenance of genetic variation for fitness. Populations may carry a heavy genetic load as a result of selection for separate genders.

No amicable divorce? Challenging the notion that sexual antagonism drives sex chromosome evolution

“…In particular, recessive, sexually antagonistic genes that benefit males should be more likely to accumulate on the X chromosome because they are expressed in the hemizygous sex [31,56]. In a series of experiments on the fruit fly Drosophila melanogaster, the majority of the genome was artificially constrained to be inherited solely though males [24,28,57,58]. Within lines with male-limited inheritance, male fitness increased, while that of females decreased.…”

Genetic Constraints and the Evolution of Display Trait Sexual Dimorphism by Natural and Sexual Selection

“…In this case, the intersexual genetic correlation for adult fitness is negative , and it has been shown using experimental evolution that when selection is removed from females, evolved fitness increases in males correspond to equal fitness decreases in females (Prasad et al 2007). Thus, while resolution of conflict over specific shared phenotypic traits may be relatively common, at any one time there may be substantial sexually antagonistic genetic variance for fitness at a genome-wide scale.…”

Sexually antagonistic genetic variance for fitness in an ancestral and a novel environment

“…A number of studies have demonstrated the existence of sexually antagonistic genetic variation for specific traits or components of fitness (Meagher 1992;Rice 1992;Gibson et al 2002;Calsbeek & Sinervo 2004;Fedorka & Mousseau 2004;Pischedda & Chippindale 2006;Prasad et al 2007). Fewer studies have reported estimates of the intersex genetic correlation for lifetime fitness: K0.85 in collared flycatchers (Qvarnström et al 2006); K0.48 in red deer ( Foerster et al 2007); and K0.16 in a laboratory population of Drosophila melanogaster .…”