Normalized substitution rate as a function of population size, in the absence of deleterious mutations. Symbols correspond to simulation results, and thick solid lines correspond to analytic predictions obtained (A,B) from Eq. (51) or (C) from Eq. (52). Thin lines in (A,B) indicate the analytic prediction without discreteness correction, i.e., without term ln[(*V*/*s*) ln(*V*/*U*_{b})] on the right-hand side of Eq. (51). Dotted lines in (B,C) indicate the analytic result by Desai and Fisher (2007), Eqs. 36, 38, and 39. Their result shown in (B) is outside of its designed validity range and is shown for reference only. The simulations were carried out (A,B) in discrete time as described (Rouzine et al., 2003) or (C) in continuous time. *V* was measured in simulation as the average slope of *k*_{av}(*t*) in the time interval [0.85*t*_{0}, 1.15*t*_{0}], where the time *t*_{0} of the interval center was determined from the condition *k*_{av}(*t*_{0}) = 250. The initial *k*_{av}(0) was set to 1.5*k*_{av}(*t*_{0}). The per-site beneficial mutation rate *μ* was chosen such that the genomic beneficial mutation rate *U*_{b} had the value shown on the plot at time *t*_{0}, *U*_{b} = *μk*_{av}(*t*_{0}). The size of the symbols roughly corresponds to the largest standard deviation of the mean speed estimates.

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