RT Journal Article
SR Electronic
T1 The Speed of Adaptation in Large Asexual Populations
JF Genetics
JO Genetics
FD Genetics Society of America
SP 2045
OP 2053
DO 10.1534/genetics.104.027136
VO 167
IS 4
A1 Wilke, Claus O.
YR 2004
UL http://www.genetics.org/content/167/4/2045.abstract
AB In large asexual populations, beneficial mutations have to compete with each other for fixation. Here, I derive explicit analytic expressions for the rate of substitution and the mean beneficial effect of fixed mutations, under the assumptions that the population size N is large, that the mean effect of new beneficial mutations is smaller than the mean effect of new deleterious mutations, and that new beneficial mutations are exponentially distributed. As N increases, the rate of substitution approaches a constant, which is equal to the mean effect of new beneficial mutations. The mean effect of fixed mutations continues to grow logarithmically with N. The speed of adaptation, measured as the change of log fitness over time, also grows logarithmically with N for moderately large N, and it grows double-logarithmically for extremely large N. Moreover, I derive a simple formula that determines whether at given N beneficial mutations are expected to compete with each other or go to fixation independently. Finally, I verify all results with numerical simulations.