Controlling species coexistence through temporal niche engineering*

The set of species that coexist in a community often determines its collective function, such as the biodegradation rate in wastewater treatment plants or the production of short-chain fatty acids in the gut. However, not all sets of species can stably coexist in any environment, and we lack general strategies to probe and control the coexistence of a given set of species (a "dream team"). Here, we develop and computationally test a general strategy to engineer a set of resources that allows a given set of species to stably coexist. We prescribe exact ratios of resource concentrations that result in any desired relative species abundances at the steady state. Our strategy relies on the engineering of temporal niches: time intervals during which the subset of resources present in the environment remains constant, relevant for laboratory serial dilution experiments or natural feast-famine cycles. By exploiting temporal variation, our algorithm can ensure coexistence despite using much fewer resources than species, thus vastly beating the competitive exclusion principle that is pervasive in ecology. Finally, our method also chooses the most structurally stable recipe among the ones possible, thus staying the most immune to the experimental error inherent in realizing any resource recipe. We believe that our community control strategy could be useful in a wide variety of cases, such as in mimicking natural ecosystems, e.g., isolated from guts, oceans, or soils, in the lab.