Belowground predator-predator interactions in the soil ecosystem

Agricultural soils teem with interacting organisms including many small arthropods. These belowground ecosystems can have a significant impact on soil health and agricultural production. Predatory mites and beetles are common in soil agroecosystems of the Inland Pacific Northwest and have potential to serve as biocontrol agents. However, little is known about their predator-predator interactions and their influence on prey populations. This study investigates the interactions between predatory mites (Mesostigmata: Laelapidae) and predatory adult beetles (Coleoptera: Staphylinidae) through behavioral bioassays. To investigate behaviors that mediate interspecific interactions between these two predators, we conducted a bioassay to observe the behavioral response of the predator (mite or beetle) when placed in close proximity to a substrate containing chemical cues from its own species, the other predator species, or a blank control. There were significant differences in certain behaviors in response to each predator’s chemical cues. A second series of bioassays investigated the ability of Staphylinidae to locate and consume mites (intraguild prey) and Collembola (prey) at different depths in the soil profile. Hemiedaphic Staphylinidae were found to locate and consume prey at different depths in the soil profile by "diving" into the soil. The data from these two assays suggest predator-predator interactions could be influenced by chemical cues released by each species. A stronger understanding of belowground predator-predator interactions will enhance our knowledge of how soil food webs function in healthy, productive agroecosystems.