Mechanisms underlying reproductive trade-offs: Costs of reproduction

The survival cost of reproduction appears, at first sight, a classic example of a life history trade-off, with increased investment of resources into reproductive processes apparently leading to fewer resources available for longevity assurance, resulting in decreased lifespan. Such trade-offs have been confirmed by phenotypic and genetic manipulative experiments. Various sources of costly activities have also been identified, especially in the model organism Drosophila, with survival costs arising from increased courtship, egg laying, and mating itself. At a deeper level, however, the mechanisms underlying such trade-offs are still relatively unknown. The idea that there is literally a finite resource pool competed for by different life history processes may not be correct, and trade-offs may instead occur because of the integration of molecular signals from different sources. This chapter summarizes the current state of knowledge on the mechanistic basis of the links between reproduction and longevity.