Biodiversity changes threaten the structure of ecological communities because species form complex interaction networks in which they are interdependent. The persistence of food webs is sensitive to changes in network structure, including the configuration of trophic modules, which are the smaller sub-webs that constitute larger networks. Theoretical advances have demonstrated that some trophic modules are more robust to perturbations than others, and that these stable modules occur more frequently than expected in empirical food webs. This suggests that these stable modules are selected for because they benefit the persistence of the entire network. We hypothesized that plant diversity moderates the sub-structure of food webs, and that networks from high diversity communities will have a greater representation of stable modules. We tested this by constructing comprehensive aboveground food webs for plots sown with 1 to 60 plant species in a long-running grassland biodiversity experiment.
Results/Conclusions
We found that the frequency distribution of three-species modules varied across the gradient of plant species richness. Stable modules occurred more commonly than unstable modules across all plots, and trophic networks from high diversity plots had a greater representation of more stable trophic modules than those from low diversity plots. These results suggest that a loss of plant biodiversity destabilizes trophic interaction networks. The implication is that low diversity webs may be more vulnerable to future disturbances.