Induced resistance mitigates the effect of plant neighbors on susceptibility to herbivores

Abstract At small spatial scales, attraction or deterrence of herbivores by plant neighbors can alter the susceptibility plants to damage (i.e., associational effects). Given patchy nature and insect herbivory, we hypothesized that induced resistance may play an important role in mitigating such variability. To test this notion, first documented neighbor effects between two closely related co‐occurring species natural populations, second, measured how these changed after inducing a common garden. In wet fields marshes Northeastern North America, boneset ( Eupatorium perfoliatum ) is primary host for herbivorous beetle Ophraella notata . Across years surveys at multiple sites, found Joe Pye weed Eutrochium maculatum was secondary O. more likely receive eggs when it grew near boneset, constituting negative effect (associational susceptibility) weed. Reciprocally, there were trends reduced (a positive effect), but pattern less consistent over space time. garden, manipulated patches, each with center (focal) surrounding (neighbor) plants, focal either hormone jasmonic acid left as controls. While prior induction mirrored surveys, most effective reducing oviposition on heterospecific groups. This effectively eliminated (susceptibility) weed, preferred species. However, conspecific had minimal species' beetles. importance variation generally ubiquity communities, suggest inducible be mechanism cope heterogeneity herbivores.