Adaptive metabolic strategies explain diauxic shifts and promote species coexistence

Authors: Leonardo Pacciani, Samir Suweis, Amos Maritan

 

Competitive systems are most commonly described mathematically using MacArthur’s consumer-resource model, leading to the “competitive exclusion principle” which limits the number of coexisting competing species to the number of available resources. Nevertheless, several empirical evidences – in particular bacterial community cultures – show that this principle is violated in real ecosystems. Another experimental evidence that cannot be explained in this framework is the existence of diauxic (or polyauxic) shifts in microbial growth curves: bacteria consume resources sequentially, using first the one that ensures the highest growth rate and then, after a lag phase, they start growing slower using the second one. By introducing adaptive metabolic strategies whose dynamics tends to maximize species’ relative fitness, we are able to explain both these empirical evidences, thus setting the paradigm for adaptive consumer-resource models.