Lifetime changes in phenotypic expression and evolutionary potential of female mating traits in Drosophila melanogaster

Abstract

Recognition of the ubiquity of female multiple mating has caused an important shift in sexual selection research, emphasizing the adaptive nature of female mating strategies. While phenotypic changes in female mating traits have been previously studied, little is known about the genetic basis of female mating behaviour and its potential to respond to selection at different stages throughout an individual's life. Using a large quantitative genetic breeding design, we observed lifetime female mating behaviour in Drosophila melanogaster to examine the effect of female age and mating history on three key mating traits: courtship latency, mating latency and copula duration. Courtship latency (time until males initiate courtship) decreased with the cumulative number of females' previous matings. Mating latency (defined here as the time between the beginning of courtship and the start of copulation) increased with female age, and copula duration was found to decrease as females aged. We calculated quantitative genetic estimates for mating traits in virgin females and at the females' third mating to examine changes in the evolutionary potential of mating traits. We found considerable additive genetic variation in courtship latency and mating latency measured in virgin females. Copula duration displayed no heritable variation among females across sire families, but male effects were consistent with the idea that this trait is under male control. Heritability estimates differed significantly from zero in virgin females for courtship latency and mating latency but not when females were mating for the third time. However, overlapping 84% confidence intervals between heritability estimates obtained from virgin and mated females suggest that female mating strategies may have the potential to respond to selection at these different life stages.