Females prefer noninfected males as mates in the grain beetle Tenebrio molitor: evidence in pre- and postcopulatory behaviours

We examined the effects of infection by the tapeworm Hymenolepis diminuta on mate choice in a wild strain of grain beetle, Tenebrio molitor. Female beetles mate multiply, so both precopulatory and postcopulatory behaviours are important to sexual selection in this species. When virgin females were allowed to choose between tethered males, one infected and one noninfected, they spent more time near and copulated more often with noninfected males than with infected males. During the 90-min trials, the majority (65%) of control females, presented with two noninfected males, copulated with both males at least once. However, females presented with one infected and one noninfected male were much less likely (30%) to be polyandrous. Among monogamous females, 81% mated exclusively with the noninfected male. Within the group of polyandrous females, contact with the second male was made earlier for those that copulated first with the infected male. Mass of males also influenced female remating behaviour. Females that first mated with larger males copulated fewer times than females that mated with smaller males. Infected males were not less sexually responsive than noninfected males, so these results are consistent with female mate choice. Overall, these results demonstrate that female beetles prefer noninfected males in both precopulatory and postcopulatory choice.