A biology study of Bactris setosa Mart and B. hatschbachii Noblick ex A. Hend was made with the aim of obtaining information about structure and spatial pattern of Bactris palm genus in different stretches in atlantic rain forest in Ubatuba-SP, to asses the population of these species in the altitude gradient. Samples were taken in six altitudes (0 m - on sea level, 100, 200, 400, 600 and 850 m) in round plots of 100 m². In these plots, the two species were measured. Populations were divided into five size class: classe 1 (acaulescent); classe 2 (1 a 50 cm); classe 3 (51 a 100 cm); classe 4 (101 a 200 cm); classe 5 (> 200 cm). Both populations present a predominance of individual in the class following the seedling class. At sea level both species were abundant (B. hatschbachii, 472 ind/ha and B. setosa, 312 ind/ha) and in the slope B. hatschbachii was more numerous in 400 m (400 ind/ha) of altitude and in 600 m B. setosa (148 ind/ha) was more numerous, in 850 m the two species were not sampled. The results of Morisita index (Id) showed that the spatial pattern for the two species populations was clumped. The populational pattern presented showed that those palm troes are restricted to favorable environment.
spatial distribution; Atlantic Rain Forest; palm ecology
