Density Patterns of<i>Piper</i>Ant‐Plants and Associated Arthropods: Top‐Predator Trophic Cascades in a Terrestrial System?¹

ABSTRACT Top‐predator (fourth‐trophic‐level) controlled trophic cascades are thought to be uncommon in terrestrial systems, but actual quantitative tests and comparisons of bottom‐up and top‐down forces in systems with more than three linear trophic levels are rare. Here, we describe the density patterns of the arthropod community associated with Piper ant‐plants in Costa Rican wet forests. Consumers in this community comprise a complex, interacting web of herbivores, predaceous ants, and predators of ants. Although the hollow stems and petioles of the Piper plants provide some protection to resident ants from predation, specialized Dipoena spiders and Phyllobaenus beetles exploit Pheidole ants inhabiting Piper plants. We report abundance patterns of plants, ants and predators in four forests. These patterns of abundance are consistent with predictions of top‐down cascades across four trophic levels when the top predators are effective (beetles). We discuss how top‐down and bottom‐up forces may interact in systems with less effective top predators (spiders).