Females Guarded by Sneaker Males Experience Higher Predation in the Two-Spotted Spider Mite

Abstract

Males often employ different reproductive tactics to gain access to females based on their condition and the surrounding environment. Predation risk is expected to have a significant influence on the frequencies of alternative reproductive tactics because these tactics typically differ in activity, which may result in differences in predation rate. In theory, such predation effects can explain the evolution as well as the maintenance of alternative reproductive tactics. Yet, there is little experimental work testing how predation risk affects alternative reproductive tactics. To assess such effects of predation, here we report on experiments with the two-spotted spider mite Tetranychus urticae. The two-spotted spider mite is a small arthropod herbivore species, in which males exhibit precopulatory mate guarding by mounting preadult moulting (and hence immobile) females. Two reproductive tactics are observed during mate guarding: The fighting tactic involves attacking other males to drive them away, while the sneaking tactic involves mounting the females and remaining motionless, even when contacted by other males. In this study, we exposed pairs of male and female spider mites to a predatory mite (Phytoseiulus persimilis) and observed their survival and male response to a predator when females were guarded by either fighter or sneaker males. We found that predation risk was not significantly different between fighter and sneaker males. However, the immobile females were more often preyed upon when guarded by sneakers than when guarded by fighters. We attribute this indirect effect of predation risk to the sneakers continuing to mount females even when a predator is nearby.