Experimentally increased brood size accelerates actuarial senescence and increases subsequent reproductive effort in a wild bird population

1. The assumption that reproductive effort decreases somatic state, accelerating ageing, is central to our understanding of life-history variation. Maximal reproductive effort early in life is predicted to be maladaptive by accelerating ageing disproportionally, decreasing fitness.
2. Optimality theory predicts that reproductive effort is restrained early in life to balance the fitness contribution of reproduction against the survival cost induced by the reproductive effort. When adaptive, the level of reproductive restraint is predicted to be inversely linked to the remaining life-expectancy, potentially resulting in a terminal effort in the last period of reproduction.
3. Experimental tests of the reproductive restraint hypothesis require manipulation of somatic state and subsequent investigation of reproductive effort and residual lifespan. To our knowledge the available evidence remains inconclusive, and hence reproductive restraint remains to be demonstrated.
4. We modulated somati...