Studies on refulation of herbivores by ants in tropical rain forests

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To elucidate the species composition, abundance and spatial distribution of ants in the forest canopy of a tropical rain forest in Borneo, ant abundance were censused in the forest canopy of 15 tree species several times in the dipterocarp forest at Lambir National Park in Sarawak, Malaysia, using the system for observation of forest canopy there. In addition, to analyze the effects of ants on the herbivores, herbivore abundance and herbivory damage on leaves of the trees were also censused. Moreover, the effects of presence of epiphytes and aerial soil in the forest canopy on the availability of nest sites for ants were studied in the field.The results suggested that few species of ants utilize space both on the ground and on trees as their home range, that spatial distribution of ant species in the forest canopy is rather stable, and that particular ant species prefer the forest canopy or epiphytes for their nest sites. A few ant species that usually use the ground surface as their home range were observed to expand the range onto the surface of the tree trunk temporarily, and ant species that settle in the domatia of some epiphytes were often observed to be dominant in the forest canopy. The home ranges of these two types of ant species showed little overlap spatially, and were likely to have indirect influences on the spatial distribution of the other species in the forest canopy. Thus, it is presumed hat there is strong interspecific competition in the ant community in the forest canopy. The data suggest the possibility that ants that colonize epiphytes might regulate the abundance of lianas and other epiphytes and indirectly affect the spatial distribution of the other ants through the regulation. The data on the relations between herbivory damage and ant abundance suggest that these ant species might significantly function as predator regulating herbivores on the trees.