Experimental design for the evolution experiments.

<p>(i) Stocks of wild isolates were grown up, each comprising a single starting genotype of each species. (ii) Experiments were started with each species in monoculture or in polyculture (all five species mixed together). (iii) To stimulate active growth and promote adaptation to the laboratory conditions, each culture was diluted 20-fold in fresh medium twice weekly for 8 wk. Tubes were shaken to prevent the formation of biofilms and maintain spatial homogeneity. Numbers of generations ranged from 60.9 to 82.2 across cultures and effective population sizes ranged from 5.3×10⁵ to 9.9×10⁶ (<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001330#pbio.1001330.s011" target="_blank">Table S3</a>). (iv) Final cultures were plated on agar. (v) Single colonies of each species were isolated for growth assays described in the main text.