Properties of adaptive walks on uncorrelated landscapes under strong selection and weak mutation |
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Authors: | Rokyta Darin R Beisel Craig J Joyce Paul |
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Affiliation: | Department of Biological Sciences, University of Idaho, Moscow, ID 83844, USA. rokyta@uidaho.edu |
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Abstract: | We examine properties of adaptive walks on uncorrelated (i.e. random) fitness landscapes starting from moderately fit genotypes under strong selection weak mutation. As an extension of Orr's model for a single step in an adaptive walk under these conditions, we show that the fitness rank of the dominant genotype in a population after the fixation of a beneficial mutation is, on average, (i+6)/4, where i is the fitness rank of the starting genotype. This accounts for the change in rank due to acquiring a new set of single-mutation neighbors after fixing a new allele through natural selection. Under this scenario, adaptive walks can be modeled as a simple Markov chain on the space of possible fitness ranks with an absorbing state at i = 1, from which no beneficial mutations are accessible. We find that these walks are typically short and are often completed in a single step when starting from a moderately fit genotype. As in Orr's original model, these results are insensitive to both the distribution of fitness effects and most biological details of the system under consideration. |
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Keywords: | Mutational landscape Extreme value theory Adaptive walk Adaptive evolution |
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