Relationships between male attractiveness, female remating, and sperm competition in the cigarette beetle

Abstract

Polyandry creates the opportunity for post-mating sexual selection, and pre- and post-mating sexual selection affects male traits. Investigation of selection pressures in both pre- and post-mating stages is necessary to understand sexual selection. In the cigarette beetle Lasioderma serricorne, we found previously that males that mated faster are thought to be more attractive in the pre-mating process. However, whether the attractive males are favored by the post-mating process remains unclear and thus we set out to investigate this. The attractive males (judged by the pre-mating process) were able to mate sooner with both virgin and non-virgin females. However, attractive males invested less in ejaculation and have difficulty keeping mated females from remating with other males. Thus, under the polyandrous condition, attractive males have a disadvantage in reproductive success due to the risk of sperm competition because they cannot prevent female remating. Therefore, whether a female remates or not would be an important factor in the reproductive success of an attractive male. On the other hand, when a female mated with two males, the last male always sires more offspring, and males who were attractive in pre-mating process did not sire more offspring. These findings suggest that attractive males are at least not favored by the post-mating process itself, and the association between pre- and post-mating sexual selection in L. serricorne is not as simple as reinforcing or undermining. Because females generally mate with multiple males, sexual selection occurs not only before copulation but also after. Thus, investigating the interplay between pre- and post-mating sexual selections is needed to understand sexual selection, but it is still relatively understudied. In the cigarette beetle, males that courted females more were favored by pre-mating processes. Such attractive males had more success mating with virgin and non-virgin females. However, females that have mated with attractive males readily remate with other males, suggesting that the attractive males cannot prevent sperm competition. Thus, the reproductive success of attractive males may be lower under the higher frequency of female remating. Furthermore, non-virgin females were unlikely to bias paternity toward attractive males. These results suggest that males that are favored by pre-mating processes are not favored by post-mating processes in this beetle.