Question: How plastic is the reproductive strategy of palm trees? Hypothesis: The onset of reproduction and sex allocation depend on both the size and the type of environment that determines the availability of resources. Organisms: The palm tree Attalea speciosa Mart. ex Spreng. It grows in both primary forests and disturbed sites. in a wide range of edaphic and climatic conditions. Field site: The Brazilian state of Para near the town of Maraba. on the commune of Benfica. The pioneer front. i.e. where primary or slightly degraded rain forest is turned into pastures by recently settled farmers. Methods: Deforestation was used as a large-scale experiment. The effect of size (number of leaves or total height) on the onset of reproduction and sex allocation was compared in three environments: a forest. a partially invaded pasture and a pure stand of palm tree (babassual). Conclusions: Reproduction starts at smaller sizes in the pasture and the babassual than in the forest. with height being a better predictor of reproduction than number of leaves in the forest. Male reproduction starts at smaller heights than female reproduction in the pasture and the babassual but not in the forest.