Selection for male aggression is associated with changes in reproductive traits, chemical signaling and lifespan in Drosophila melanogaster

Life history traits are all essential traits linked to development, survival and reproduction, directly influencing individual fitness. Limited environmental or physiological resources force organisms to balance competing demands, leading to fundamental trade-offs, particularly between survival and reproduction. Male aggression is often assumed to enhance reproductive success, yet its broader association with other fitness-related traits remains unclear. To address this, we used Drosophila melanogaster Bully lines selected for high levels of male aggression, to examine relationships between aggression, chemical signaling, and essential life-history traits including reproductive behaviors and lifespan. Our results reveal that Bully A males exhibit a shift in a major life-history trade-off, with reduced reproductive performance accompanied by increased lifespan. Bully A males exhibited lower mating success, shorter mating duration and less effective chemical mate-guarding. However, this was traded-off with increased lifespan, enabling more reproductive opportunities. We also uncover potential mechanistic underpinnings of the reproductive deficits. Bully males showed differences in their cuticular hydrocarbon (CHCs) profiles and transferred lower levels of cVA to females, a mate-guarding pheromone, thereby weakening their post-mating strategy. Overall, our findings indicate that selection for male aggression is associated with a shift in a key life-history trade-off, highlighting aggression as an evolutionary force shaping adaptation of life-history traits and providing a foundation for future genetic and mechanistic studies.