The genomic consequences of sexual selection
Mallet, Martin A.
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Sex-differences in phenotype, development, and life-history can alter the strength of selection experienced by males and females. In particular, theoretical models have demonstrated that differences in the strength of selection between the sexes can influence the deleterious mutation load of populations. Stronger selection acting on males, via the action of sexual selection, could lower the mutation load for females if deleterious mutations tend to be harmful for both sexes. The necessary data to evaluate these models have been lacking, however, as most empirical studies of mutations have overlooked the fundamental differences between the sexes. Using the IV laboratory-adapted population of Drosophila melanogaster, I have measured the sex-specific impact of mutations in both sexes. This was done both for mutations naturally segregating in IV and for new mutations occurring on the X-chromosome. For both classes of mutations, males suffered a greater selective cost than females, and the mutations responsible were deleterious in both sexes. Further characterization of the male fitness phenotype revealed widespread decline in sexually selected characters combined with an increase in the correlation between sexually selected traits and viability, indicative of pleiotropy between new mutations. My work establishes the necessary conditions for sexual selection to reduce the mutation load of females, and helps fill a crucial gap in our understanding of the consequences of deleterious mutations.