Biodiversity, productivity and stability in real food webs

The global biodiversity crisis has motivated new theory and experiments that explore relationships between biodiversity (species richness and composition in particular), productivity and stability. Here we emphasize that these relationships are often bi-directional, such that changes in biodiversity can be both a cause and a consequence of changes in productivity and stability. We hypothesize that this bi-directionality creates feedback loops, as well as indirect effects, that influence the complex responses of communities to biodiversity losses. Important, but often neglected, mediators of this complexity are trophic interactions. Recent work shows that consumers can modify, dampen or even reverse the directionality of biodiversity-productivity-stability linkages inferred from the plant level alone. Such consumer mediation is likely to be common in many ecosystems. We suggest that merging biodiversity research and food-web theory is an exciting and pressing frontier for ecology, with implications for biodiversity conservation.