title: Properties of adaptive walks on uncorrelated landscapes under strong selection and weak mutation.
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.
authors.affiliation: Department of Biological Sciences, University of Idaho, Moscow, ID 83844, USA. rokyta@uidaho.edu
authors.forename: Darin R
authors.initials: DR
authors.lastname: Rokyta
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Beisel
authors.forename: Paul
authors.initials: P
authors.lastname: Joyce
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics*; D000818:Animals; D019143:Evolution, Molecular; D005838:Genotype; D008957:Models, Genetic; D009154:Mutation; D012641:Selection, Genetic