Disentangling multiple predator effects in biodiversity and ecosystem functioning research

Disentangling the effects of predator loss can be complex as predators exert a suite of direct and indirect effects in ecosystems. O'Connor & Bruno manipulated predator abundance, richness, and composition in experiments with and without prey dispersal in an estuarine ecosystem. They observed effects of predator presence and composition on prey assemblages, particularly in experiments without prey dispersal, but they found no effect of predator richness on prey assemblage. Here, we discuss the role of non-additive, antagonistic, and spatial effects of predators in biodiversity and ecosystem functioning experiments, with a particular focus on the results of O'Connor & Bruno.