Nectar- and pollen-gathering Cephalotes ants provide no protection against herbivory: a new manipulative experiment to test ant protective capabilities

The question if ant behaviour and biological limitations should be considered before generalisations about the ant's defensive capabilities in ant-plant relationships was explored through a new experimental manipulation. In the Brazilian tropical savanna, we tested the protective action of Cephalotes pusillus Klug on the extrafloral nectar-bearing plant Ouratea spectabilis Engl. (Ochnaceae). Three treatments were performed: control (free ant access), Cephalotes-treatment (access permitted only to C. pusillus), and ant free treatment (no ants). No difference was found in the levels of leaf herbivory among experimental stems. Visitation by different ant species to control stems translated into significantly greater fruit and seed production by this stem category than by ant-free and Cephalotes-treated stems. Thus, results showed that an investigation of system's natural history, ant's morphological traits, defensive capabilities and behaviour are needed before a protective role is inferred to each associated ant species.