Publications filtered by: Ageing
Recognition of the ubiquity of female multiple mating has evoked an important shift in sexual selection research, emphasising 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. Heritability estimates did not differ significantly from zero 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.
The trade-off between survival and reproduction is fundamental to life history theory. Sexual selection is expected to favour a live fast die young life history pattern in males due to increased risk of extrinsic mortality associated with obtaining mates. Sexual conflict may also drive a genetic trade-off between reproduction and lifespan in females. We found significant additive genetic variance in longevity independent of lifetime mating frequency, and in early life mating frequency. There was significant negative genetic covariance between these traits indicating that females from families characterized by high levels of multiple mating early in life die sooner than females that engage in less intense early life mating. Thus, despite heritable variation in both traits, their independent evolution is constrained by an evolutionary trade-off. Our findings indicate that, in addition to the well-known male-driven direct costs of mating on female lifespan (mediated by male harassment and the harmful effects of male seminal fluids), females with a genetic propensity to mate multiply live shorter lives. We discuss the potential role of sexual conflict in driving the evolutionary trade-off between reproduction and lifespan in Drosophila. More generally, our data show that, like males, females can exhibit a live fast die young life history strategy.
In many species, females exposed to increased sexual activity experience reductions in longevity. Here, in Drosophila melanogaster, we report an additional effect on females brought about by sexual interactions; an effect that spans generations. We subjected females to a sexual treatment consisting of different levels of sexual activity, and then investigated patterns of mortality in their offspring. We found reduced probabilities of survival, increases in the rate-of-senescence, and a pattern of reduced mean longevities, for offspring produced by mothers that experienced higher levels of sexual interaction. We contend that these effects constitute trans-generational costs of sexual conflict – the existence or implications of which have rarely been considered previously. Our results indicate that ongoing exposure by mothers to male pre-copulatory interactions is itself sufficient to drive trans-generational effects on offspring mortality. Thus, we show that increases in maternal sexual activity can produce trans-generational effects that permeate through to latter life-stages in the offspring. This helps to elucidate the complex interplay between sex and ageing, and provides new insights into the dynamics of adaptation under sexual selection.