Habitat structure and population persistence in an experimental community

Understanding spatial population dynamics is fundamental for many questions in ecology and conservation(1-4). Many theoretical mechanisms have been pr oposed whereby spatial structure can promote population persistence, in par ticular for exploiter-victim systems (host-parasite/pathogen, predator-prey ) whose interactions are inherently oscillatory and therefore prone to exti nction of local populations(5-11). Experiments have confirmed that spatial structure can extend persistence(11-16), but it has rarely been possible to identify the specific mechanisms involved. Here we use a model-based appro ach to identify the effects of spatial population processes in experimental systems of bean plants (Phaseolus lunatus), herbivorous mites (Tetranychus urticae) and predatory mites (Phytoseiulus persimilis). On isolated plants , and in a spatially undivided experimental system of 90 plants, prey and p redator populations collapsed; however, introducing habitat structure allow ed long-term persistence. Using mechanistic models, we determine that spati al population structure did not contribute to persistence, and spatially ex plicit models are not needed. Rather, habitat structure reduced the success of predators at locating prey outbreaks, allowing between-plant asynchrony of local population cycles due to random colonization events.