Effects of population growth on the success of invading mutants

Understanding if and how mutants reach fixation in populations is an important question in evolutionary biology. We study the impact of population growth has on the success of mutants. To systematically understand the effects of growth we decouple competition from reproduction; competition follows a birth–death process and is governed by an evolutionary game, while growth is determined by an externally controlled branching rate. In stochastic simulations we find non-monotonic behaviour of the fixation probability of mutants as the speed of growth is varied; the right amount of growth can lead to a higher success rate. These results are observed in both coordination and coexistence game scenarios, and we find that the ‘one-third law’ for coordination games can break down in the presence of growth. We also propose a simplified description in terms of stochastic differential equations to approximate the individual-based model. •Population growth affects the success of a mutant in stochastic evolutionary games.•For clarity we model growth as neutral and decoupled from selection.•We find that the success of the mutant depends non-trivially on the rate of growth.•This effect is observed in both coexistence and coordination games.•By adding growth, the one-third rule of coordination games can be violated.