Dual ant attraction in the Neotropical shrubUrera baccifera(Urticaceae): the role of ant visitation to pearl bodies and fruits in herbivore deterrence and leaf longevity

Abstract

SummaryThis study investigated the protective role of ants against phytophagous insects onUrera baccifera(L.) Gaudich.Ants (22 species) visit shrubs ofU. bacciferathroughout 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 butterfliesSmyrna blomfildia(Fruhstorfer) andUrbanus esmeraldus(Butler), and the mothPleuroptya silicalis(Guené).The proportion of vegetative (no flowers or fruits) individuals ofU. bacciferaoccupied 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 ofU. bacciferaincreased larval mortality ofS. blomfildia, suggesting that ants attracted to pearl bodies reduce herbivore survival. Fruits were also demonstrated to play an important role in ant attraction byU. baccifera. Ant visitation to pearl body‐producing shrubs of non‐myrmecophyticPiper amalagoL. withU. bacciferafruits attached was significantly higher than toP. amalagoplants with an attached leaf ofU. baccifera.Ant‐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 ofU. baccifera. Additionally, in both years ant‐excluded plants had significantly faster leaf abscission rates compared with ant‐visited plants.So far, all ant–plant systems with dual food rewards involve extrafloral nectar as one of the attractants. This study withU. bacciferais 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.