RT Journal Article
SR Electronic
T1 Loss of Least-Loaded Class in Asexual Populations Due to Drift and Epistasis
JF Genetics
JO Genetics
FD Genetics Society of America
SP 2125
OP 2134
DO 10.1534/genetics.108.089136
VO 179
IS 4
A1 Jain, Kavita
YR 2008
UL http://www.genetics.org/content/179/4/2125.abstract
AB We consider the dynamics of a nonrecombining haploid population of finite size that accumulates deleterious mutations irreversibly. This ratchet-like process occurs at a finite speed in the absence of epistasis, but it has been suggested that synergistic epistasis can halt the ratchet. Using a diffusion theory, we find explicit analytical expressions for the typical time between successive clicks of the ratchet for both nonepistatic and epistatic fitness functions. Our calculations show that the interclick time is of a scaling form that in the absence of epistasis gives a speed that is determined by size of the least-loaded class and the selection coefficient. With synergistic interactions, the ratchet speed is found to approach zero rapidly for arbitrary epistasis. Our analytical results are in good agreement with the numerical simulations.