CONTRASTING DYNAMICS OF A MUTATOR ALLELE IN ASEXUAL POPULATIONS OF DIFFERING SIZE
Article first published online: 4 MAR 2012
© 2012 The Author(s).
Volume 66, Issue 7, pages 2329–2334, July 2012
How to Cite
Raynes, Y., Gazzara, M. R. and Sniegowski, P. D. (2012), CONTRASTING DYNAMICS OF A MUTATOR ALLELE IN ASEXUAL POPULATIONS OF DIFFERING SIZE. Evolution, 66: 2329–2334. doi: 10.1111/j.1558-5646.2011.01577.x
- Issue published online: 3 JUL 2012
- Article first published online: 4 MAR 2012
- Received June 16, 2011, Accepted January 6, 2012, Data Archived: Dryad doi:10.5061/dryad.v0v58gd5
- asexual populations, clonal interference, hitchhiking, mutation rate, population size, yeast
Mutators have been shown to hitchhike in asexual populations when the anticipated beneficial mutation supply rate of the mutator subpopulation, NUb (for subpopulation of size N and beneficial mutation rate Ub) exceeds that of the wild-type subpopulation. Here, we examine the effect of total population size on mutator dynamics in asexual experimental populations of Saccharomyces cerevisiae. Although mutators quickly hitchhike to fixation in smaller populations, mutator fixation requires more and more time as population size increases; this observed delay in mutator hitchhiking is consistent with the expected effect of clonal interference. Interestingly, despite their higher beneficial mutation supply rate, mutators are supplanted by the wild type in very large populations. We postulate that this striking reversal in mutator dynamics is caused by an interaction between clonal interference, the fitness cost of the mutator allele, and infrequent large-effect beneficial mutations in our experimental populations. Our work thus identifies a potential set of circumstances under which mutator hitchhiking can be inhibited in natural asexual populations, despite recent theoretical predictions that such populations should have a net tendency to evolve ever-higher genomic mutation rates.