Abstract
Current theory predicts that intraguild predation, the killing and eating of species that use similar resources and are thus potential competitors, often leads to exclusion of species and destabilization of food webs. This is in contradiction with the observation that intraguild predation occurs frequently in natural ecosystems. However, critical tests of the theory are lacking, mainly because the resource is difficult to characterize in the experimental systems used until now. A critical test will either confirm the existing theory or reject it, the last result indicating that the current models are too simplistic, and further experimental and theoretical studies should the reveal mechanisms for coexistence with intraguild predation. The most essential parameter for the model predictions is the productivity of the habitat: coexistence of a system of 3 species with intraguild predation is only possible for intermediate productivity. Hence, experiments testing the theory should measure the effects of manipulating productivity on coexistence and persistence of the species. We propose to perform such experiments using two simple acarine systems. These systems have the advantage over experimental systems used so far that the resource level (i.e. productivity) is easy to manipulate experimentally, that the generation time of the mites are short, and the species are easy to maintain on small experimental arenas. One system will be used to test the current theory, while the other will serve to investigate the often-occurring reciprocal intraguild predation (i.e. when 2 competitors eat each other’s juvenile stages), parallel to further development of models to include the effects of such, commonly occurring reciprocal intraguild predation.
Netherlands