Female mating with multiple males within a single fertile period (polyandry) is a common phenomenon in animal kingdom. Conventional wisdom assumes that males are selected to maximize their paternity, females are choosy for the best possible sire. However, some female insects are particularly promiscuous. Behavioral scientists and evolutionary biologists have long been puzzled by why females mate with multiple males despite potential costs such as expenditure of time and energy, reduced life span, risk of predation and contracting sexually-transmitted diseases. In the red flour beetle (Tribolium castaneum), a major pest of stored grain products, females usually obtain sufficient sperm to retain fertility for several months from a single insemination, but they copulate repeatedly even within minutes the after first mating. Previous studies have demonstrated that polyandry in this species does not confer direct fitness benefits to the females, but enhance F1 male fitness and reduces F1 female fitness with laboratory inbred strains. This project will examine the genetic benefits/costs associated with polyandry and post-copulatory mechanisms that lead to enhanced offspring fitness in T. castaneum. Specific questions to be addressed are: 1) is the fitness tradeoff between sons and daughters of polyandrous females observed in laboratory inbred strains a general phenomenon for field outbred populations, and 2) are the superior sons and inferior daughters sired by the same males or different males?
This study will advance our knowledge on inter-sexual conflict and its consequences for species evolution. This research will significantly enhance our understanding of the evolution of mating systems and reproductive strategies. Because the red flour beetle is an important pest of stored grain products, the results help to develop new strategies for pest control through better understanding of its mating behavior and factors regulating population dynamics.