The role of dispersal in acarine predator – prey interactions: Experiments and model simulations

Abstract: To understand the role played by between-plant dispersal in population dynamics ofinteracting populations of prey and predators, and to assess how short- and long-distancemovements of individuals affect biological control of a herbivore pest by means of naturalenemies, we conducted a series of small-scaled greenhouse experiments with two-spottedspider mites (Tetranychus urticae) and the phytoseiid predator Phytoseiulus persimilis. Anexperimental set-up consisted of either 30 or 45 potted bean plants arranged in a lattice. Theplants were placed on a water-saturated blanket to inhibit movement of mites from one plant toanother. Instead mites could disperse by crossing bridges between neighboring plants. Threetypes of system were established: System A with no bridges; System B in which a plant wasconnected to the four nearest plants in the lattice; and System C in which plants were connectedto the eight nearest neighbors. At the beginning of an experiment, some of the plants wereinoculated with adult female spider mites, and two weeks later the plants were inoculated witha few adult female predators. The population dynamics of prey and predators were followedover a period of 30 weeks. The results show that connectivity (defined by the number of bridgesbetween plants) promoted biological control by increasing the spatial overlap between predatorsand prey, and by increasing the predator-prey ratio. However, high connective also increasedthe risk that the predator population goes extinct before all prey has been eliminated. Astochastic, spatially explicit, simulation model was applied to simulate the experiments.Overall, the model’s predictions agreed well with the experimental results.