Aggressive trait selection influences life-history trade-offs, favoring survival over reproductive success in Drosophila melanogaster males

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 often enhances reproductive success by improving resource acquisition and mate competition. However, the broader impact of high levels of aggression on individual overall fitness and life-history trade-offs remains poorly understood. To address this, we used the Drosophila melanogaster Bully line, derived from wild-type flies (Canton-S line) through artificial selection for high levels of male aggression, and assess whether increased aggressiveness influences male life-history traits. Our results reveal that increased male aggressiveness shifts the balance of a major life-history trade-off, favoring survival over reproductive success. Bully 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 demonstrate that selection for male aggression profoundly influence 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.