Intraspecific variation in longevity of Drosophila prolongata (Diptera: Drosophilidae) under solitary and group conditions

Considerable variations in behavior and physiology exist among sexes and strains of species. The amount and allocation of energy resources can affect the health and survival of individuals. If an individual devotes a large amount of energy to interact with other conspecifics, the resources may become too scarce to maintain their physical condition, which could reduce longevity. In this study, I examined the interactive effects of sex, strain, and the presence of conspecifics on adult longevity using four strains of Drosophila prolongata. This species shows a large intraspecific variation in behavior and morphology among isofemale strains. Under solitary conditions, longevity was significantly different among strains for both sexes. The effects of same-sex conspecifics on adult longevity were also highly variable between the sexes and among strains. When exposed to conspecifics, the longevity of males of a hyper-aggressive strain was more notably decreased than that of females of the same strain or either sex of other less aggressive strains. These results indicate that differences in the balance of costs and benefits of social interactions lead to differences in adult longevity under group conditions between the sexes and among strains within the same species.