Recurrent selection and evolutionary dynamics of a GNP.

(A) Estimated genotype dynamics during adaptive evolution. The time of introduction of each new mutation (dotted circles) is estimated on the basis of detecting an allele frequency of at least 5% in the population. Some mutations were clustered based on their similarity in the dynamics (see Figure S11). The temporal order of mutations that occurred in rapid succession (white arrows) was determined on the basis of their allele frequencies in the final evolved population estimated using deep sequencing data (Figure S7). (B) Fitness estimates of 8 backcrossed strains, representing all possible combinations of alleles that comprise the GNP, from clone 3 isolated from the ammonium-limitation selection were determined by direct competition with either the ancestral or the gat1-2/lst4-2/mep2-2 genotypes. Error bars are 95% CI of the regression coefficient. (C) Fitness landscape reconstruction based on the fitness estimates for the 8 genotypes. The selection coefficient values of each strain are represented as color intensity. The width of each edge is proportional to the difference in fitness between two genotypes that edges connect. A solid line indicates a favored path whereas a dashed line indicates a disfavored path. Selection favors thicker, solid lines in the evolutionary trajectory.