title: On the findability of genotypes.
abstract: Can we define a measure that describes how easy or difficult it is for a population to evolve to a specific genotype? For populations evolving under weak mutation on a time-invariant fitness landscape, I argue that one appropriate measure is the expected waiting time, starting from equilibrium, for a population to become fixed for a given genotype. Under this definition for the "findability" of genotypes, I show that for any pair of genotypes (1) a population at equilibrium is always more likely to fix at the more findable before the less findable genotype and (2) the expected time to evolve from the more findable to the less findable genotype is always greater that the expected time to evolve in the opposite direction. Although increasing the fitness of a genotype always increases its findability, in general there is no simple relationship between the rank ordering of genotypes by fitness and the rank ordering of genotypes by findability. I also present a method for quantifying the relative contributions of mutation, selection, substitution rate, and probability of reversion to a genotype's findability.
authors.affiliation: Biology Department, Duke University, Box 90338, Durham, North Carolina, 27708; Current Address: Lynch Labs, Room 204K, Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, 19104. davidmc@sas.upenn.edu.
authors.forename: David M
authors.initials: DM
authors.lastname: McCandlish
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D056084:Genetic Fitness; D005838:Genotype; D008957:Models, Genetic; D009154:Mutation; D011153:Population / Q000235:genetics
keywords: Constraint; evolvability; fitness landscape; reversible Markov chain; weak mutation