Evolutionarily stable coexistence in a single nutrient: optimization and cross-feeding

Two questions on coexistence have perplexed community ecologists for nearly a century: first, the "paradox of the plankton", that nature world possess tremendous diversity while theoretical models suggested the number of species can hardly exceeds the number of nutrients. Second, evolution has been shown to exacerbate this paradox. As species are constantly evolving towards optimality, which may produce a supreme winner that takes over the habitat. To investigate these questions, we utilized and extended the graphical tools of resource-competition theory to relate and unify multiple models for microbial diversity, and quantified the optimal metabolic strategies in resource competition models in general. This framework was then applied to metabolic models that allows species to increase dimension in nutrient space by secreting metabolites. With this simple model, we explored the possibilities of coexistence though cross-feeding on a single supply nutrient, and investigated general criteria for such co-existence to be evolutionarily stable.