Table 1 . Summary of commonly used variables and parameters.

	Descriptions
Ud	Deleterious mutation rate in nonmutators
λUd	Deleterious mutation rate in mutators
x	Negative log fitness of an individual (larger x corresponds to lower fitness)
ρ(x)	Distribution of fitness effects of deleterious mutations
R(k)	Laplace transform of ρ(x)
M	Difference between mutator and nonmutator deleterious mutation rates
γ	Mutation rate from nonmutators to mutators
fn(x,t)	Distribution of fitnesses of nonmutators at time t
fm(x,t)	Distribution of fitnesses of mutators at time t
F{n,m}(k,t)	Laplace transform of fn(x,t) or fm(x,t)
σ	Effect of a typical deleterious mutation
α	Defined as M/σ
δn,δm	Average deleterious load of nonmutators or mutators respectively
pm	Fraction of mutators in the total population
τ	Average lifetime of a single mutator lineage
η	Backmutation rate from mutators to nonmutators
Ub,λUb	Beneficial mutation rate in nonmutators or mutators respectively
N	Population size
sb	Fitness advantage provided by a beneficial mutation
s	Fitness advantage of a beneficial mutant relative to population mean fitness