Statistical and Biological Physics

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Evolutionary dynamics in growing populations

Anna Melbinger, Jonas Cremer and Erwin Frey

Existing theoretical models of evolution focus on the relative fitness advantages of different mutants in a population while the dynamic behavior of the population size is mostly left unconsidered. In this work we introduce an agent-based stochastic model which combines the growth dynamics of the population and its internal evolution. Our model thereby accounts for the fact that both evolutionary and growth dynamics are based on individual reproduction events and hence are highly coupled and stochastic in nature. We exemplify our approach by studying the dilemma of cooperation in growing populations and show that genuinely stochastic events can ease the dilemma by leading to a transient but robust increase in cooperation. In more detail, the increase is caused by an asymmetrical amplification of demographic fluctuations. While stochastic events towards more cooperation are amplified by a growth advantage, stochastic events leading to less cooperation are hindered (see the movie for an illustration).