Figure 1.

Food web associated with Baccharis salicifolia. Solid lines with arrowheads indicate direct effects among trophic levels. Dashed lines with circles indicate trait-mediated indirect effects, where plant diversity indirectly affects one species by directly affecting the traits of another and thus mediates their pairwise interaction (e.g. plant diversity influences the attractiveness of herbivores and, in so doing, indirectly influences enemy/mutualist abundance through changes in per capita interaction rates). Density-mediated indirect effects occur through the product of sequential direct effects (e.g. plant diversity influences the density of herbivores and, in so doing, indirectly influence enemy/mutualist abundance without changes in per capita interaction rates). Because we do not manipulate parasitoid presence/absence, the effects of parasitoids on aphids and ants were not quantified.