Does developmental environment affect sexual conflict? An experimental test in the seed beetle

Sexual conflict is widespread and may be mediated by the environment. By manipulating water available to seed beetles during development, we explore the effect of this important resource on mating interactions and reproductive performance. We found that more water during development has the potential to increase male ejaculate size, but this ability is only realized when mating with female reared with no access to water. Sexual conflict and sexually antagonistic coevolution are driven by differences in reproductive interests between the sexes. There have been numerous studies focused on how both the social and physical environment that individuals experience as adults, or where mating occurs, mediate the intensity of sexual conflict. However, how the physical environment that juveniles experience, mediates their later mating interactions, is still poorly understood. In seed beetles, Callosobruchus maculatus, water is an important resource that can impact fitness and reproduction. Here, we manipulated the water content of beans that beetles were reared in and explored how this environmental variation affects mating interactions and subsequent male and female fitness. We measured the mass of ejaculate transferred, mating behavior, female fecundity, and offspring production as well as male and female lifespan. We found that males reared in wet environments transferred a larger ejaculate to females, but only when females were reared in dry environments. We also found that females mated to males reared in dry environments laid more eggs than those mated to males from wet environments. Additionally, eggs laid by females reared in dry conditions had greater survival when they had mated to males reared in dry than wet environments. Overall, however, there were no treatment effects on the number of adult offspring females produced nor male or female adult lifespan, thus it is difficult to determine the evolutionary implications of these results. Our research provides evidence for the importance of developmental environment for determining the expression of adult mating and fitness traits.

Automated summary

This study investigates the impact of water availability during development on mating interactions and reproductive performance in seed beetles. The results suggest that male seed beetles reared in wet environments have the potential to transfer a larger ejaculate to females, but only when the females were reared in dry environments. Additionally, females mated to males reared in dry environments lay more eggs and the offspring from these matings have higher survival rates when reared in dry conditions.