A coordinated response to environmental drivers amongst individual functional traits is central to the plant strategy concept. However, whether the trait co-ordination observed at the global scale occurs at other ecological scales (especially within species) remains an open question. Here, for sapling communities of two tropical dry forest types in Costa Rica, we show large differences amongst traits in the relative contribution of species turnover and intraspecific variation to their directional changes in response to environmental changes along a successional gradient. We studied the response of functional traits associated with the leaf economics spectrum and drought tolerance using intensive sampling to analyse inter- and intra-specific responses to environmental changes and ontogeny. Although the overall functional composition of the sapling communities changed during succession more through species turnover than through intraspecific trait variation, their relative contributions differed greatly amongst traits. For instance, community mean specific leaf area changed mostly due to intraspecific variation. Traits of the leaf economics spectrum showed decoupled responses to environmental drivers and ontogeny. These findings emphasise how divergent ecological mechanisms combine to cause great differences in changes of individual functional traits over environmental gradients and ecological scales. Functional trait values, height and crown illumination index for each treeThis dataset gives the value of leaf functional traits (mean value for the three, or fewer, measured leaves), height and crown illumination index for 852 sapling trees belonging to 69 species of Costa Rican tropical dry forests.data_Derroire_etal_2017_ScientificReport_sapling.csvEnvironmental factors in successional tropical dry forests of Costa RicaThis dataset gives the values of environmental factors (micro-climate, soil physical and chemical properties, forest structure) of 12 plots in successional tropical dry forests of Costa Rica.data_Derroire_etal_2017_ScientificReport_enviro.csvSpecies codesThis file gives the list of species measured in a study of sapling in successional tropical dry forests of Costa Rica, their families, and the species code used in the dataset of functional traits.data_Derroire_etal_2017_ScientificReport_species.csv