PT - JOURNAL ARTICLE
AU - Waxman, D.
TI - Population Growth Enhances the Mean Fixation Time of Neutral Mutations and the Persistence of Neutral Variation
AID - 10.1534/genetics.112.139220
DP - 2012 Jun 01
TA - Genetics
PG - 561--577
VI - 191
IP - 2
4099 - http://www.genetics.org/content/191/2/561.short
4100 - http://www.genetics.org/content/191/2/561.full
SO - Genetics2012 Jun 01; 191
AB - A fundamental result of population genetics states that a new mutation, at an unlinked neutral locus in a randomly mating diploid population, has a mean time of fixation of ∼4Ne generations, where Ne is the effective population size. This result is based on an assumption of fixed population size, which does not universally hold in natural populations. Here, we analyze such neutral fixations in populations of changing size within the framework of the diffusion approximation. General expressions are derived for the mean and variance of the fixation time in changing populations. Some explicit results are given for two cases: (i) the effective population size undergoes a sudden change, representing a sudden population expansion or a sudden bottleneck; (ii) the effective population changes linearly for a limited period of time and then remains constant. Additionally, a lower bound for the mean time of fixation is obtained for an effective population size that increases with time, and this is applied to exponentially growing populations. The results obtained in this work show, among other things, that for populations that increase in size, the mean time of fixation can be enhanced, sometimes substantially so, over 4Ne,0 generations, where Ne,0 is the effective population size at the time the mutation arises. Such an enhancement is associated with (i) an increased probability of neutral polymorphism in a population and (ii) an enhanced persistence of high-frequency neutral variation, which is the variation most likely to be observed.