Figure 4.

MeCoCos as a level of organization. (a) The symbols represent different species, where the same shape represents similar metabolic capabilities (functionally redundant groups), which would lead to competitive interaction (dotted lines) owing to a high niche overlap. On the other hand, members of different functional groups may engage in commensal or mutualistic relationships, driven by metabolic complementarity (solid lines). (b) A rearrangement of the left network leads to a new representation, in which members related through complementary functions tend to co-occur, forming MeCoCos, which constitute an intermediate level of organization between the species and the community levels. Understanding community-level dynamics may thus be simplified to understanding how MeCoCos compete (figure 5). (c) The interaction matrix corresponding to the networks has a block structure that makes it feasible to build population dynamics models as in macroscopic systems (e.g. [45–47]). Blue blocks represent competitive interactions, and red blocks represent mutualistic interactions arising from metabolic complementarity.