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Distribution of arthropods in homogeneously and heterogeneously induced plant patches.
Rodriguez-Saona, Cesar1, Thaler, Jennifer*,1, 1 University of Toronto, Toronto, ON, Canada
ABSTRACT- Plant responses to herbivore damage can affect future colonization of herbivores and their natural enemies. In nature, plants commonly occur in patches, surrounded by other plants of the same species. Field experiments were conducted to address how varying the number of plants damaged by herbivores within a patch affect colonization of herbivores and their natural enemies. Because herbivore damage causes changes in plants that can negatively affect the performance of herbivores and also induces volatiles that attract natural enemies to these plants, we hypothesized that patches with higher amounts of herbivore damage might contain reduced number of herbivores, while recruiting higher numbers of natural enemies of the herbivores. To test this hypothesis, tomato plants were randomly assigned into one of three patch types: homogenoeus patch (damaged), where all plants within a patch were damaged by placing a S. exigua larva on each plant; heterogeneous patch, where one plant per patch was damaged; and homogeneous patch (undamaged), where plants within the patch received no damage. All patches consisted of three tomato plants. The data supported our predictions that herbivores are more abundant on undamaged homogeneous patches, and predators are more abundant in patches with high herbivore damage. Omnivores responded more similarly to herbivores than predators. In heterogeneous patches, damage to plants did not affect the number of arthropods on undamaged neighboring plants.
Key words: induced defenses, arthropod distribution, plant patches, natural enemies