Competition and Nest Spacing in a Tropical Stingless Bee Community

The density and dispersion patterns of nests of 5 stingless bee species are described for a tract of Costa Rican tropical dry forest. Features of suitable nest sites are analyzed, but it does not appear that nest site availability limits colony density or determines colony dispersion. Rather, food limitation is suggested by a linear relationship between the logarithm of colony biomass and the logarithm of foraging "home range." Colonies were uniformly dispersed intraspecifically in 4 species. The pattern in a 5th species could not be distinguished from a random dispersion. Partial nest counts in 3 more species suggested a clumped dispersion in at least 1 species. The 4 species with uniform nest spacing all use pheromones for recruitment in foraging, whereas the remaining 4 species do not. The 3 most uniformly dispersed species are also intraspecifically aggressive at food sources. We propose that colony spacing is accomplished in these species by aggressive prevention of new colony establishment. The mechanism of colony spacing we propose has as essential elements: pheromone marking of potential nest sites; recruitment of workers; and aggression between workers from rival nests. This mechanism has been observed in operation in at least 1 of the species.