title: Muller's ratchet and the pattern of variation at a neutral locus.
abstract: The levels and patterns of variation at a neutral locus are analyzed in a haploid asexual population undergoing accumulation of deleterious mutations due to Muller's ratchet. We find that the movement of Muller's ratchet can be associated with a considerable reduction in genetic diversity below classical neutral expectation. The extent to which variability is reduced is a function of the deleterious mutation rate, the fitness effects of the mutations, and the population size. Approximate analytical expressions for the expected genetic diversity are compared with simulation results under two different models of deleterious mutations: a model where all deleterious mutations have equal effects and a model where there are two classes of deleterious mutations. We also find that Muller's ratchet can produce a considerable distortion in the neutral frequency spectrum toward an excess of rare variants.
authors.affiliation: Instituto Gulbenkian da Ciência, P-2781-901 Oeiras, Portugal.
authors.forename: Isabel
authors.initials: I
authors.lastname: Gordo
authors.forename: Arcadio
authors.initials: A
authors.lastname: Navarro
authors.forename: Brian
authors.initials: B
authors.lastname: Charlesworth
mesh_terms: D005075:Biological Evolution; D014644:Genetic Variation; D008957:Models, Genetic; D009010:Monte Carlo Method; D009154:Mutation; D012641:Selection, Genetic