Artificial selection for increased reproductive effort accelerates actuarial senescence and reduces lifespan in a precocial bird

Life-history theory and evolutionary theories of ageing predict that trade-offs between reproduction and somatic maintenance shape the evolution of ageing and lifespan. However, the significance of these trade-offs remains debated, as previous correlational studies have produced inconsistent results. Here, we used an experimental artificial selection approach in a precocial bird, the Japanese quail (Coturnix japonica), to directly test this fundamental tenet. We found that selection for divergent reproductive effort affected adult survival, with shorter lifespans in individuals selected for higher reproductive effort compared with individuals selected for lower reproductive effort at generations five and six. This difference in lifespan was driven by accelerated actuarial senescence rather than changes in baseline mortality. No differences in reproductive senescence were observed between the selection treatments. Our findings provide experimental evidence that vertebrate mortality trajectories can evolve rapidly in response to selection and demonstrate that increased reproductive effort is intrinsically linked to faster ageing and a shorter lifespan-thereby supporting a central tenet of life-history and ageing theory.