Figure 3. Fitness effects of individual mutations.

a, b, Mutation trajectories in an asexual (a) and sexual (b) line. Orange mutations are significantly beneficial; blue are deleterious; gray are unmeasured or consistent with neutrality. Several mutations were present in the founding population and hence omitted from Figures 1 and 2. c, Identities and fitness effects of significantly beneficial or deleterious mutations (chromosome number in parenthesis). Asterisks indicate fitness effects measured from reconstructions (mean of six replicate fitness assays, error bars ±s.e.m.); other fitnesses are from sequencing-based assay (error bars ±s.e. of regression coefficient; Methods). Italicized mutations are synonymous.