THE EFFECTS OF MANAGEMENT-SYSTEMS ON GROUND-FORAGING ANT DIVERSITY IN COSTA-RICA

The impacts of four different management systems on diversity of ground-foraging ants were examined to assess potential for conservation of biological diversity in human-influenced agricultural or agroforestry systems. Using a variety of indices, diversity was measured along a gradient of anthropogenically disturbed habitats. The gradient, in terms of increasing levels of disturbance, ranged from primary rain forest, abandoned cacao plantations, productive cacao plantations, to banana plantations. The primary forest and abandoned cacao plantations were situated in a reserve and the productive cacao plantations, and banana plantations were located on privately owned land within 35 km of the reserve in the Sarapiqui Valley of Costa Rica. To sample ground-foraging ants, we placed tuna baits along the ground in each habitat. Although tuna baits attract a generalist assemblage of ants that may be better able to adapt to more disturbed sites, diversity of this community was significantly reduced with increased disturbance. Ant diversity was not different for forest and abandoned cacao sites except in terms of evenness, with the forest having a more even distribution of species. Forest and abandoned cacao sites were significantly more diverse than both productive cacao and banana plantations. The latter two did not differ significantly from each other in terms of diversity, but there was considerable variability within each of these habitat types. The results of this study suggest that conservation of diversity may be possible in a ''mosaic'' of different land uses, but further studies, such as those addressing the importance of scale and nearby source populations, are necessary before management practices can be implemented.