Sexual Conflict and Sexual Selection in the Indian Meal Moth, Plodia interpunctella.

Abstract

Sexual conflict is a powerful evolutionary force, arising due to the differing reproductive interest of the sexes. As males and females contrast in what they require to increase their own relative fitness, this creates sexual conflict. This thesis investigates sexual conflict and sexual selection in the Indian meal moth Plodia interpunctella, a species known to be under strong intralocus sexual conflict for shared life-history traits and fitness. Through the use of experimental evolution, we altered the adult mating sex ratio to either male biased or female biased. This changes the selective forces between populations that may directly impact on intralocus sexual conflict. Male biased populations were found to have increased reproductive success for both sexes with corresponding changes in shared life-history traits compared to the female biased populations. Divergence between the two treatments is further supported by male biased populations showing increased protection from a natural viral pathogen. Post-copulatory sexual selection was examined in males through the sterile male method. Males evolving under a male biased sex ratio were subject to increased selection on traits involved in sperm competition from rival males’ ejaculates, yet sired the same total number of offspring as males evolving under a female biased sex ratio. Sexual selection is a non-mutually exclusive force acting in tandem with sexual conflict, potentially causing increased reproductive success and immunity protection in the male biased populations. Fecundity selection was examined in a stock population of P. interpunctella. Lifetime fecundity was increased without corresponding changes or trade-offs with body size or longevity, two life-history traits known to be important to increased reproductive success in females. Finally, the effects of dietary protein and carbohydrates were examined using the geometric framework. Sexually antagonistic selection over macronutrients was evident, with sexes showing preference for protein and carbohydrate in opposing regions of the nutrient landscape, indicating that intralocus conflict is unlikely to have been resolved in this moth species.