The investigators propose to study the biological diversity, community structure, and energetics of a Neotropical rain forest canopy ant assemblage. Although ants are thought to be, in general, predators and scavengers, they are probably the most abundant arthropod group in tropical forests trees. Their abundance poses an ecological paradox, because predators should not be more abundant than the herbivores on which they feed. The investigators will test the hypothesis that most rain forest canopy ants derive the bulk of their energy from plant resources and function essentially as primary rather than secondary consumers, which may enable them to support comparatively dense populations. Small patches of forest canopy on the mainland adjacent to Barro Colorado Island, Panama, will be treated with insecticidal fog to determine the composition of the local arboreal ant assemblage and the relative contribution of ants to the biomass of canopy arthropods; field observations of the foraging behavior of several of the most abundant ant species will determine the relative importance of animal and plant matter to their diets; and, the caloric content of their major dietary components for these species will be quantified in order to obtain an estimate of the degree to which they rely on plant matter as a source of energy. By revealing the taxonomic composition of a rain forest canopy ant assemblage, determining the relative abundance of ants in arboreal arthropod communities, and exploring the extent to which the reliance of ants on plant-derived energy may help explain their abundance, this comprehensive research project will enhance our understanding of fundamental aspects of the biology of tropical forest canopies.
