Philosophical Transactions of the Royal Society B: Biological Sciences
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Beneficial mutations and the dynamics of adaptation in asexual populations

Paul D. Sniegowski

Paul D. Sniegowski

Department of Biology, University of Pennsylvania, Philadelphia, PA 19063, USA

[email protected]

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and
Philip J. Gerrish

Philip J. Gerrish

Department of Biology, University of New Mexico, Albuquerque, NM 87131-0001, USA

Department of Mathematics, Centro de Matemática e Aplicações Fundamentais, University of Lisbon, 1649-003 Lisbon, Portugal

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    We discuss the dynamics of adaptive evolution in asexual (clonal) populations. The classical ‘periodic selection’ model of clonal evolution assumed that beneficial mutations are very rare and therefore substitute unfettered into populations as occasional, isolated events. Newer models allow for the possibility that beneficial mutations are sufficiently common to coexist and compete for fixation within populations. Experimental evolution studies in microbes provide empirical support for stochastic models in which both selection and mutation are strong effects and clones compete for fixation; however, the relative importance of competition among clones bearing mutations of different selective effects versus competition among clones bearing multiple mutations remains unresolved. We provide some new theoretical results, moreover, suggesting that population dynamics consistent with the periodic selection model can arise even in a deterministic model that can accommodate a very high beneficial mutation rate.

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