The relationship between environmental complexity, species diversity and productivity in a natural reconstructed yeast community

Diversity, whether ecological or genetic, is widely believed to be beneficial to the functioning of ecosystems. Although many studies have investigated relationships between environmental complexity, species diversity and ecosystem function, few have examined these factors simultaneously. We propagated combinations of three naturally coexisting yeast species for 200 generations, in environments of increasing complexity represented by combinations of up to eight different carbon sources. We found that competitive ability was transitive, and not related to productivity, which was equal among the species. Species diversity had a positive effect on productivity and overyielding in mixtures was caused primarily by complementation. Environmental complexity and species diversity were positively correlated, though not significantly, and the sole case of coexistence of all three yeasts after 200 generations occurred on a single carbon source, melezitose. Environmental complexity also enhanced productivity, although this relationship failed, for unknown reasons, at the highest level of complexity. Our results suggest that maintaining species diversity contributes to ecosystem productivity, but that the mechanisms responsible for maintaining diversity may not be straightforward.