Stanton 9726663 There has long been an interest in ecology in understanding the mechanisms that allow competing species to coexist. Numerous questions remain in this area. This research would take advantage of a widespread occurrence of ant-acacia symbioses in a region of Kenya to observe, experiment with, and model interactions between competing species. In arid upland regions, Acacias dominate the limited numbers of trees present. These species, as in other dry tropical habitats exhibit a mutualistic relationship with ants. The presence of ants substantially decrease tree mortality and derive substantial benefits from the ants themselves. There are four symbiotic ant species occurring throughout this region where they exhibit a distinct hierarchy in competitive interactions. Individual trees are colonized by a single ant species and there are aggressive interactions among the ant species for the occupation of each tree with one species being the usual dominant. At the same time, however, the four ant species have persisted in the region for an extended time and this project will test the factors that foster this continued coexistence. It will remove ants experimentally from some trees, examine recolonization of such tree as well as of potted trees that had been allowed to grow without ants, and combine this information in a matrix model that predicts the transitions that occur in the occurrence of each ant species within the region. This work will have substantial effects for conservation planning and educational development in Kenya.