Male age, mating probability, and progeny fitness in the bulb mite

Abstract

In many species, the accumulation of mutations in the male germline can result in decreased progeny fitness. Consequently, females may evolve preferences for younger partners. Here, we used a promiscuous and relatively long-living bulb mite (Rhizoglyphus robini) to test whether male age affects his progeny fitness. We found that daughters of 4- to 5-week-old males had a 6% lower fecundity than those of 4- to 8-day-old males. Furthermore, we investigated whether male age and female mating status affect the probability of copulation. Male age classes did not differ in motility measured in the presence of females, but older males were less likely to mate within an hour of pairing. We had predicted that females' reluctance to mate with older males would be revealed by their higher motility after the physical contact between the sexes. However, postcontact female motility was not affected by male age, nor was it a significant predictor of the occurrence of copulation. Apart from male age, mating probability was affected by female mating status, with virgin females copulating more readily than females that had mated multiply before the experiment. The interaction between male age and female mating status was not significant. It took less time for males to locate virgin females, and a higher proportion of virgins mated. Higher male motility in the presence of virgin females suggests that they may use sexual pheromones to attract males, whereas females that have already copulated may avoid the costs of mating by suppressing emission of sexual attractants.