Spent-media experiments reveal high levels of functional redundancy among representative isolates; (A) proportional growth of each isolate (rows) in the spent-media (120 h) of another isolate (columns); the color of each square represents overlap of resource use between two isolates, in the proportion of reduced growth compared to growth in fresh FL media, on a scale of 0–1; early isolates (top left box) are represented with purple background color, and late isolates (bottom right box) are represented with green background color; isolates marked with ^* were further selected for the four-isolate model community; (B) relationship between pairwise FD of nine isolates estimated via metabolic pathway (KEGG module) distributions in genomes and average pairwise functional overlap measured via spent-media experiments; isolate pairs were divided into three categories depending on whether they belonged to the same early or late assembly group; isolate pairs that represent the final four-isolate model community are represented in triangles; (C) functional overlap measured in 48 h versus 120 h spent-media experiments for the strains in the four-isolate model community; for each pair of isolates, reciprocal functional overlaps (Isolate 1 growing in spent-media of Isolate 2, and vice versa) are shown; error bars represent standard deviations (n = 3).