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arXiv · 1007.1340

Stochastic slowdown in evolutionary processes

Philipp M. Altrock·Chaytanya S. Gokhale·Arne Traulsen
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Abstract

We examine birth--death processes with state dependent transition probabilities and at least one absorbing boundary. In evolution, this describes selection acting on two different types in a finite population where reproductive events occur successively. If the two types have equal fitness the system performs a random walk. If one type has a fitness advantage it is favored by selection, which introduces a bias (asymmetry) in the transition probabilities. How long does it take until advantageous mutants have invaded and taken over? Surprisingly, we find that the average time of such a process can increase, even if the mutant type always has a fitness advantage. We discuss this finding for the Moran process and develop a simplified model which allows a more intuitive understanding. We show that this effect can occur for weak but non--vanishing bias (selection) in the state dependent transition rates and infer the scaling with system size. We also address the Wright-Fisher model commonly used in population genetics, which shows that this stochastic slowdown is not restricted to birth-death processes.

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Philipp M. Altrock, Chaytanya S. Gokhale, Arne Traulsen. 2010-07-08. Stochastic slowdown in evolutionary processes. https://doi.org/10.1103/physreve.82.011925

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