Non-consumptive effects of spiders on herbivore and carnivore prey: occurrence, importance, and mechanisms

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In trophic interactions, predator effects on prey populations through consumption are often exceeded by non-consumptive effects that predators elicit on prey behavior. Spiders can elicit strong antipredator behavior in both insects and other spiders. However, antipredator behavior has only been investigated in a limited number of insect and spider species. In addition, the mechanisms involved in the detection of predation risk (i.e., predator presence) have rarely been explored in terrestrialsystems.In subproject A, we will investigate the occurrence and strength of antipredator behavior across 18 spider and 18 insect species that cover a wide taxonomic range. The selection of study species will allow to test effects of life-history traits on the magnitude of antipredator behavior. Traits include hunting mode of the predator, relative body size of predator and prey, trophic level, niche width and dispersal ability of the prey. Measured antipredator behavior will include both small-scale movement and the propensity for long-distance dispersal. Furthermore, effects of the presence of predator cues on plant performance will be tested in the field.In subproject B, we will use bioassays and analytical methods to investigate how the presence of spider predators is detected by prey species. Spider silk, feces, chemical footprints, and airborne volatile cues will be distinguished as pathways for predation risk detection. Further, mechanical and chemical cues of spider silk will be separated. We will test if predation risk is detected via tactile senses, olfaction and/or contact chemoreception. Finally, the substances involved in risk detection will be identified using gas chromatography and mass spectrometry.