The purpose of this research is to determine how ecological factors shape facultative mutualisms, focussing on ant-plant system. The proposed studies of the relationship between the plants and their ant occupants, of the life history characters of the ant species that occupy the plants, and of ecological interactions between ant species will contribute to our understanding of how facultative ant-plant mutualisms are established and maintained. Ecological investigations such as those outlined in this proposal can identify likely selective environments in which future evolutionary specialization may take place. Comparative research of the interaction between the ant-plant Conostegia setosa (Melastomataceae) and its ant occupants at two rainforest sites, one in Costa Rica and one in Panama is being conducted. Since each species of ant occupant potentially has a different effect on plant fitness, the identity and frequency of each species of ant occupant and how the identity of the occupants is determined are important in predicting the likelihood of the evolution of more specialized mutualisms. Experiments are designed to address several ecological factors that may determine the occupants of C. setosa: by: 1) observing interactions between the species of ant occupants and other area ant species at baits, 2) comparing life history variables such as colony structure, foraging strategies, and competitive behaviors that may affect establishment in C. setosa plants by the different species of ant occupants, and 3) measuring the benefits of the interaction to the plants and the ants. A long-term transplant experiment has been set up to investigate modes of colonization by each ant species, priority effects, and the influence of the ant community on the identity of the ant occupants.
