Figure 2. Fitness Trajectories of Evolving Strains.

Fitness trajectories of haploid (A) and diploid (B) strains; each line in (A) and (B) represents one single evolving strain. Haploidized diploids are indicated with a red dashed line. The mean of all strains of a condition and ploidy, averaged over all strains is shown in (C). In (C), all haploid and diploid strains were scaled relative to their haploid or diploid ancestor; diploids were scaled to the haploid ancestor upon haploidization. The mean rate of adaptation is given by the slope of the fitness trajectories and is also shown in (C). Of the 20 replicate populations that began as diploids (B), four reverted to haploidy in the course of the experiment; they are shown with a red dashed line; their mean trajectory is shown separately in (C). Error bars represent the standard error of the mean. All mean slopes (C) are higher than zero (t-tests; * t ₁₄ = 2.15, p = 0.049; ** t ₁₅ = 3.50, p = 0.0032; *** t ₃ = 34.6, p < 0.0001).