Submitted to: Environmental Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/10/2005
Publication Date: 8/1/2005
Citation: Campbell, J.F. 2005. Fitness consequences of multiple mating on female Sitophilus oryzae (L.)(Coleoptera: Curculionidae). Environmental Entomology 34: 833-843. Interpretive Summary: The rice weevil is a major pest of stored grain. The number of offspring produced by an insect is often a function of the number of times that females mate, but variation in the costs and benefits of multiple mating can have wide ranging implications for pest behavior and ecology that ultimately impact pest population dynamics. This study demonstrated that the costs and benefits of multiple mating for female rice weevils in terms of number of offspring produced and female longevity were dependent on the number of males present and the number of copulations that occurred. A single copulation did not enable females to lay eggs over their complete lifespan, so multiple matings did increase lifetime reproduction. However, as the number of matings increased there was a decline in number of offspring and female lifespan. These complex interactions suggest a conflict in terms of the benefits for male and female rice weevils that will likely impact male-female interactions, spatial distribution, and population dynamics.
Technical Abstract: The fitness consequences of multiple mating for the seed parasite Sitophilus oryzae (L.) (Coleoptera: Curculionidae) were investigated. In the first of a series of experiments, the impact of multiple mating on female fitness was determined by evaluating the impact of a single mating period with one male, continuous exposure to one male, and continuous exposure to five males. Continuous exposure to one male increased lifetime fecundity by extending the period of time progeny were produced compared to a single mating period with one male, although average progeny size was reduced. Exposure to five males significantly reduced female survival and the number and size of progeny produced compared to the other treatments. In the second experiment, the number of progeny and the length of time progeny could be produced from a single copulation were determined. Females became sperm depleted within 7±1 weeks after laying 259±22 progeny, but a second mating period 9 weeks after the first copulation extended progeny production. Third, the mechanism for the decline in progeny production at high male densities was determined to be reduced oviposition, due at least in part to a high proportion of time spent in copula. In the final experiment, virgin females were shown to respond positively to males, but mated and sperm depleted females were neutral in their response to males. Multiple mating has costs and benefits for females that vary with the number of copulations and these are likely to impact population dynamics.