Induced biotic responses to herbivory and associated cues in the Amazonian ant-plant Maieta poeppigii

Ants inhabiting ant-plants can respond to cues of herbivory, such as the presence of herbivores, leaf damage, and plant sap, but experimental attempts to quantify the dynamic nature of biotic defenses have been restricted to a few associations between plants and ants. We studied the relationship between certain features of the ant-shrub Maieta poeppigii Cogn. (Melastomataceae) and the presence or absence of ant patrolling on the leaf surface in plants occupied by the ant Pheidole minutula Mayr (Hymenoptera: Formicidae). We also carried out field experiments to examine ant behavior following plant damage, and the potential cues that induce ant recruitment. These experiments included clipping of the leaf apex, as well as the presentation of a potential herbivore (live termite worker) and a foliar extract from Maieta on treatment leaves. The presence of ants patrolling the leaves of M. poeppigii is influenced by the number of domatia on the plant. Ant patrolling on the leaves of M. poeppigii was constant throughout a 24 h cycle, but the mean number of patrolling ants decreased from young to mature leaves, and from leaves with domatia to those without domatia. There was an overall increase in the number of ants on experimental leaves following all treatments, compared to control leaves. Visual and chemical cues associated with herbivory are involved in the induction of ant recruitment in the Maieta–Pheidole system. The continuous patrolling behavior of ants, associated with their ability to respond rapidly to foliar damage, may result in the detection and repellence/capture of most insect herbivores before they can inflict significant damage to the leaves.