Influences of aging and mating history in males on paternity success in the red flour beetle Tribolium castaneum

The investment of males in reproductive traits is often associated with their age. For example, several empirical and theoretical studies have demonstrated that older males make greater investment in reproduction compared with younger males. However, with regards to post-copulatory sexual selection, male reproductive success might be influenced by decreasing sperm quality with male age and the interaction between aging and mating experience in males. However, only a few studies that investigated influences of male aging as well as male mating experience on their post-copulatory sexual selection. In this study, we investigated paternity success influenced by the post-copulatory sexual selection of males at different ages in the red flour beetle Tribolium castaneum. To investigate the effects of the mating experience, the paternity success of older males who had experienced multiple matings (mated male) was compared with older males who had not experienced mating (naive male). The results of this study revealed that paternity success was not affected by male aging. In fact, naive old males exhibited significantly higher paternity success compared with old males who had previously mated. These results suggest that an interaction between male aging and their mating experience affected their paternity success, but not male aging. Our study has demonstrated that male aging affects their reproductive success in a complex interaction of multiple factors in T. castaneum.