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A SELECTION MODEL OF MOLECULAR EVOLUTION INCORPORATING THE EFFECTIVE POPULATION SIZE
Author(s) -
Ellegren Hans
Publication year - 2009
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.2008.00560.x
Subject(s) - biology , fixation (population genetics) , genetic drift , population , selection (genetic algorithm) , directional selection , allele , allele frequency , frequency dependent selection , population size , balancing selection , natural selection , evolutionary biology , population genetics , effective population size , genetics , genetic variation , computer science , gene , demography , sociology , artificial intelligence
Evolution implies changes in allele frequencies over generations. Eventually, unless subject to balancing selection pressures, alleles segregating in a population are destined to arrive at either of two endpoints, loss or fixation. The probability of fixation is influ enced by several factors that may vary over space and time, and also interact with each other. Population structure (spatial sepa ration coupled with nonrandom mating among demes) and immi gration are examples of such factors (Whitlock and Gomulkiewicz 2005). In addition, selection and drift also drive the fixation pro cess. Directional Darwinian selection favors certain genotypes at the expense of others and will enhance the spread of advan tageous alleles in the population so that the likelihood for their fixation is increased. Random genetic drift on the other hand is a phenomenon that arises from a stochastic process in which sam pling in finite populations result in allele frequency change purely due to chance events. Selection and drift act in concert, and the stochastic nature of drift means that variant alleles can change in frequency in a direction opposed to that incurred by their selective advantage or disadvantage. Generally, we should expect the im portance of drift to increase with decreasing selection coefficients (s, the relative fitness of individuals carrying a variant allele) of nonneutral alleles.