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Distribution of fixed beneficial mutations and the rate of adaptation in asexual populations.

TitleDistribution of fixed beneficial mutations and the rate of adaptation in asexual populations.
Publication TypeJournal Article
Year of Publication2012
AuthorsGood, BH, IM Rouzine, Balick, DJ, Hallatschek, O, Desai, MM
JournalProc Natl Acad Sci U S A
Volume109
Issue13
Pagination4950-5
Date Published2012 Mar 27
ISSN1091-6490
KeywordsAdaptation, Physiological, Genetic Fitness, Mutation, Population Density, Probability, Reproduction, Asexual
Abstract

When large asexual populations adapt, competition between simultaneously segregating mutations slows the rate of adaptation and restricts the set of mutations that eventually fix. This phenomenon of interference arises from competition between mutations of different strengths as well as competition between mutations that arise on different fitness backgrounds. Previous work has explored each of these effects in isolation, but the way they combine to influence the dynamics of adaptation remains largely unknown. Here, we describe a theoretical model to treat both aspects of interference in large populations. We calculate the rate of adaptation and the distribution of fixed mutational effects accumulated by the population. We focus particular attention on the case when the effects of beneficial mutations are exponentially distributed, as well as on a more general class of exponential-like distributions. In both cases, we show that the rate of adaptation and the influence of genetic background on the fixation of new mutants is equivalent to an effective model with a single selection coefficient and rescaled mutation rate, and we explicitly calculate these effective parameters. We find that the effective selection coefficient exactly coincides with the most common fixed mutational effect. This equivalence leads to an intuitive picture of the relative importance of different types of interference effects, which can shift dramatically as a function of the population size, mutation rate, and the underlying distribution of fitness effects.

DOI10.1073/pnas.1119910109
Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID22371564
PubMed Central IDPMC3323973
Grant ListR01 GM086793 / GM / NIGMS NIH HHS / United States
R01GM 086793 / GM / NIGMS NIH HHS / United States
R37CA 089441 / CA / NCI NIH HHS / United States
R01AI 063926 / AI / NIAID NIH HHS / United States
R37 CA089441 / CA / NCI NIH HHS / United States
R01 AI063926 / AI / NIAID NIH HHS / United States

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