Fig. 1.

Production of the lab-derived “mixed” population. (1) All 20 wild strains (for simplicity only six are depicted (i–vi)) were cultured under “paternal” and “maternal” conditions (solid and dashed oval “Petri dishes”). Colonial growth on SGF is shown as gray circles. (2) Spores of like mating type were pooled and used to fertilize wild strains of the opposite type. (3) The progeny (ascospores) from all successful crosses were pooled and (4) cultured both under paternal and maternal conditions. (5) Spores from all paternal plates were harvested, pooled, and used to fertilize colonies on all maternal plates. (6) The resulting progeny were pooled and grown at a large population size under paternal conditions. Spores from these plates were harvested and frozen. This spore pool constitutes the mixed population. (7) Mixed strains are strains of single spore origin from the mixed population. (8) Growth and spore selection lines each originated from a sub-sample of the mixed population. See text and SI Methods for the actual numbers and identities of wild strains used, and numbers of spores and colonies at each step. Diagram features not to scale