Harshavardhan Thyagarajan PhD Candidate, Chippindale Lab Intralocus sexual conflict explored through male-limited selection in Drosophila melanogaster Intralocus sexual conflict (IaSC) arises from the opposing forces of sex-specific selection pressures and positive genetic trait correlations between sexes, impacting the evolutionary genetics of sexually reproducing populations. This conflict is implicated in maintaining genetic variance for fitness, shaping trait dimorphism and influencing sex-biased gene expression. However, direct tests of its contributions remain limited and challenging. Here, I present findings from a sex-limited selection experiment using Drosophila melanogaster haplotypes, artificially ‘resolving’ IaSC under male-limited (ML) selection without opposing female fitness selection. I estimate heritable variance for fitness in selected and matched control (MC) lines. In alignment with theory, I observed increased estimates of male fitness and a sharp decline in heritable variance for the same in selected lines. Surprisingly however, I found no significant improvement in selected male fitness compared to controls under generic test conditions, challenging both the findings about genetic variance, and assumptions about ubiquity of IaSC in D melanogaster lab populations. Female fitness of selected haplotypes declined as predicted. Upon further investigation, this system reveals substantial impact of selection from unforeseen sources, likely obscuring our ability to identify adaptive responses to a release from IaSC. I demonstrate evidence of local adaptation to a novel environment of sexual selection and compensatory adaptations in a new genetic background, in the form of nuclear recovery from mother’s curse and adaptations to unique Y chromosomes. These results highlight the complexity of selection experiment design, raising concerns about the generality and accuracy of previous findings.
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