The role of antipredator behavior in an experimental community of jumping spiders with intraguild predation

 The role of direct and indirect interactions in intraguild predation (IGP) was investigated in a laboratory study. The study system contained two spider species, Phidippus audax and Phidippus octopunctatus, and the fruit fly, Drosophila melanogaster. P. audax and P. octopunctatus eat D. melanogaster. P. audax (top predators) also eat P. octopunctatus (intermediate predators). Thus, P. audax and P. octopunctatus compete for the shared resource and also interact as predator and prey. Experiments consisted of two treatments: risk-IGP and full-IGP. In the risk-IGP treatments, I examined the effects of trait-mediated indirect effects generated by antipredator behavior of P. octopunctatus on the survival of fruit flies. P. audax chelicerae were waxed so that P. audax could not attack a prey. The result indicated a significant positive indirect effect of P. audax on the survival of D. melanogaster due to the antipredator behavior of P. octopunctatus (a trait-mediated indirect effect). In the full-IGP treatments, P. audax chelicerae were not restricted, so that it could attack prey; this resulted in decreased survival of D. melanogaster. Because of predation of P. audax on P. octopunctatus, even stronger positive interactions occurred between P. audax and D. melanogaster in full-IGP than in risk-IGP. Received: May 7, 2002 / Accepted: June 27, 2002