Fitness costs of polyandry to female cigarette beetle Lasioderma serricorne

Abstract

Although polyandry is common, it is often unclear why females mate with multiple males. While polyandry may provide females with direct or indirect fitness benefits, it can also be costly. Thus, investigating both the costs and benefits of polyandry is needed to understand the evolution of female polyandry. Here, we investigated the potential benefits and costs of polyandry to females of the cigarette beetle Lasioderma serricorne. We established two treatments: single mating and remating treatments. In the remating treatment, females had the opportunity to remate with a second male. This treatment had two outcomes, that is, acceptance or rejection of mating with the second male. Adult lifespans were shorter in females that accepted and rejected remating than the singly mating female, and there was no difference in lifetime fecundity. This suggests that polyandry is costly to the female and that the cost is due to excessive courting by second mates. Indeed, the direct cost was greater when the second mate was an attractive male. Moreover, we found no difference in offspring quality between females that mated once, accepted, or rejected an additional mating, indicating no indirect benefit of polyandry. Thus, polyandry is thought to carry fitness costs but not benefits to females in L. serricorne. Polyandry, in which females mate with multiple males, often provides females with fitness benefits, but it can sometimes be costly. Because the adaptive significance of polyandry remains controversial, investigating a cost-benefit balance of polyandry is needed to understand the evolution of female multiple mating. Thus, relationships between fitness consequences and polyandry have to be carefully investigated, and we focused on fitness consequences of females that mated singly, accepted, or rejected remating. When females of the cigarette beetle L. serricorne were courted by two males, the female lifespan decreased compared with singly mated female, even if the females did not experience multiple mating. This indicates a direct fitness cost to females due to contact with two males. Additionally, we found no difference in offspring quality between monandrous and polyandrous females. This suggests no indirect benefit of polyandry. In conclusion, polyandry is thought to carry female fitness costs in the cigarette beetle.