Deterministic and stochastic regimes of asexual evolution on rugged fitness landscapes

We study the adaptation dynamics of an initially maladapted asexual population with genotypes represented by binary sequences of length L. The population evolves in a maximally rugged fitness landscape with a large number of local optima. We find that whether the evolutionary trajectory is deterministic or stochastic depends on the effective mutational distance d_eff up to which the population can spread in genotype space. For d_eff=L, the deterministic quasispecies theory operates while for d_eff <1, the evolution is completely stochastic. Between these two limiting cases, the dynamics are described by a local quasispecies theory below a crossover time T_X, while above T_X, the population gets trapped at a local fitness peak and manages to find a better peak either via stochastic tunneling or double mutations. In the stochastic regime d_eff <1, we identify two subregimes associated with clonal interference and uphill adaptive walks, respectively. We argue that our findings are relevant to the interpretation of evolution experiments with microbial populations.

Key Words: asexual, evolution

This article has been cited by other articles:

				O. J. Burton and J. M. J. Travis The Frequency of Fitness Peak Shifts Is Increased at Expanding Range Margins Due to Mutation Surfing Genetics, June 1, 2008; 179(2): 941 - 950. [Abstract] [Full Text] [PDF]

				S.-C. Park and J. Krug Clonal interference in large populations PNAS, November 13, 2007; 104(46): 18135 - 18140. [Abstract] [Full Text] [PDF]

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