Trophic cascades in a complex terrestrial community

To test for direct and indirect effects of a top predator on three lower trophic levels, we conducted two multiyear predator addition experiments in a tropical wet forest. Periodic additions of a top predator (predatory clerid beetle) to a wet forest understory shrub caused a reduction in the predatory beetle's prey (a predatory ant), increased herbivory, and reduced leaf area of the plant. These effects occurred whether beetles were added to naturally occurring shrubs or to reproductive fragments, suggesting fitness effects of top predators through three trophic levels. A correlational study showed that trophic effects of top predators also cascaded to nearby conspecifics in the forest understory. We use trends from understory plant surveys to suggest mechanisms by which these cascades could ultimately affect species diversity in the local plant community.