Community in a simplified diversity graph. A simple diversity graph consisting of the strain-nodes v, u, k and m. Edges are assigned between metabolically different strains. As strains v and k are metabolically similar, either v or k can form a community with u, both are metabolically redundant. On the other hand, the strains u, k and m are different from each other forming a community of size 3. The identification of strain communities is reduced to identification of cliques in a diversity graph.