- 1This study investigated the protective role of ants against phytophagous insects on Urera baccifera (L.) Gaudich. Ants (22 species) visit shrubs of U. baccifera throughout the year and forage especially on leaves, where they harvest pearl bodies, and on fruiting branches, where they collect fleshy fruits. The main leaf herbivores are the butterflies Smyrna blomfildia (Fruhstorfer) and Urbanus esmeraldus (Butler), and the moth Pleuroptya silicalis (Guené).
- 2The proportion of vegetative (no flowers or fruits) individuals of U. baccifera occupied by ants greatly surpassed that of neighbouring plant species lacking food rewards, consistent with the hypothesis that pearl bodies act as ant attractants. Ant visitation to vegetative individuals of U. baccifera increased larval mortality of S. blomfildia, suggesting that ants attracted to pearl bodies reduce herbivore survival. Fruits were also demonstrated to play an important role in ant attraction by U. baccifera. Ant visitation to pearl body-producing shrubs of non-myrmecophytic Piper amalago L. with U. baccifera fruits attached was significantly higher than to P. amalago plants with an attached leaf of U. baccifera.
- 3Ant-exclusion experiments showed that ants effectively reduce the incidence of lepidopteran larvae on the plants. In both 2003 and 2004, herbivores were more abundant on ant-excluded than on ant-visited shrubs of U. baccifera. Additionally, in both years ant-excluded plants had significantly faster leaf abscission rates compared with ant-visited plants.
- 4So far, all ant–plant systems with dual food rewards involve extrafloral nectar as one of the attractants. This study with U. baccifera is the first to report food bodies and fruits as ant attractants in a non-symbiotic ant–plant interaction. This facultative system is also unique in that herbivore deterrence caused by pearl body- and fruit-harvesting ants can also add to leaf longevity.