Life history and mutation rate joint evolution

The cost of germline maintenance gives rise to a trade-off between lowering the deleterious muta-tion rate and investing in life history functions. Therefore, life history and the mutation rate evolve jointly, but this coevolution is not well understood. We develop a mathematical model to analyse the evolution of resource allocation traits affecting simultaneously life history and the deleterious mutation rate. First, we show that the invasion fitness of such resource allocation traits can be approximated by the basic reproductive number of the least-loaded class; the expected lifetime pro-duction of offspring without deleterious mutations born to individuals without deleterious mutations. Second, we apply the model to investigate (i) the joint evolution of reproductive effort and germline maintenance and (ii) the joint evolution of age-at-maturity and germline maintenance. This analysis provides two biological predictions. First, under higher exposure to environmental mutagens (e.g. oxygen), selection favours higher allocation to germline maintenance at the expense of life history. Second, when exposure to environmental mutagens is higher, life histories tend to be faster with individuals having shorter life spans and smaller body sizes at maturity. Our results suggest that mutation accumulation via the cost of germline maintenance is a major force shaping life-history traits.