Late-life reproduction in an insect: terminal investment, reproductive restraint or senescence

1. The Terminal Investment, Reproductive Restraint or Senescence theories may explain individual late-life patterns of reproduction. The terminal investment hypothesis predicts that individuals increase reproductive allocation late in life as prospects for future survival decrease. The other two hypotheses predict reduced reproduction late in life, but for different reasons. Under the Reproductive Restraint hypothesis, individuals restrain their reproductive effort to sustain future survival and gain more time for reproducing, whereas under the Senescence process, reproduction is constrained because of somatic deterioration. While these hypotheses imply that reproduction is costly, they should have contrasted implications in terms of survival after late reproduction and somatic maintenance.

2. Testing these hypotheses requires proper consideration of the effects of age-dependent reproductive effort on post-reproduction survival and age-related somatic functions. We experimentally tes...