Minimizing co-growth as a unifying principle for robust communities

Natural and experimental observations have shown that members of microbial communities often show successive growth phases via a variety of mechanisms (e.g. resource utilization, spatial structure, physiological transitions). It is unclear, however, what, if any, benefits are conferred by such growth patterns. Here we demonstrate that community robustness in fact requires this minimization of temporal co-growth. In complex environments, communities with low co-growth (i.e distinct species grow rapidly at different times) are more robust against fluctuations than communities in which species are growing with heavy overlap. The diverse mechanisms of distinct communities, such as chemotaxis to create spatial structure or cross-detoxification, can be understood as specific solutions driven by local necessity to achieve more separated growth and increase community robustness. A unique feature of this mode of coexistence is that the impact of a loss of any one species on diversity becomes dramatically higher (similar to the removal of a keystone species), even though minimizing co-growth decreases the likelihood of losing a species in the first place.