Questions: We investigated tree floristic variation among the Neotropical Non-Flooded Evergreen Forests (NEF). We addressed the following questions: (a) which are the floristic groups among NEF and how are they correlated with environmental variables; (b) how many species, genera and families are shared between these floristic groups and which species are unique and indicative of each one; and (c) how does species richness vary between NEF groups? Location: Neotropical region. Methods: We used cluster and ordination analyses based on 518,004 tree occurrence data available in the NeoTropTree database to identify floristic groups throughout NEF. From the floristic groups identified here, we (a) verified correlations between floristic composition and precipitation, temperature, altitude, and latitude; (b) calculated the number of shared species, genera and families, and identified taxa unique to each group; and (c) obtained indicator species and estimated species richness for these floristic groups. Results: We recorded 172 families, 1,276 genera and 15,134 species in 1,885 sites of NEF. The families most rich in species were Fabaceae, Rubiaceae and Myrtaceae. We identified nine groups among the NEF, which broadly correspond to floristic provinces reported in the literature. Altitude and annual mean temperature were associated with a species turnover gradient from Amazon to Andean Cloud Forest. Atlantic Forest (south) and Mesoamerica plus Caribbean (north) represented the extremes of a latitudinal gradient. The Atlantic Forest presented the largest number of exclusive and indicator species (2,477 and 265, respectively), while the Amazon showed the highest species richness (6,167 species). Conclusions: Although it was possible to separate NEF into distinct floristic groups, this floristic dissociation seems to be recent, since it found support only in species data. The floristic groups identified in this study are largely congruent with their geographic distribution and spatial/ecological isolation, and seem to reflect historical, geological and climatic events that occurred in the Neotropics.

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Questions We examined the drivers of tree species variation across Neotropical non‐flooded evergreen forests (NNFEFs) to answer the following questions: can floristic groups be differentiated based on environmental predictors? How do bioclimatic, topographic, edaphic predictors and dispersal barriers contribute to explain the floristic variation throughout NNFEFs? Location Neotropical region. Methods Based on 1,843 sites (circular areas with a diameter of 10 km), 15,072 species and 509,793 occurrence records of trees, as well as on environmental variables (42 bioclimatic, 13 edaphic and four topographic variables) and dispersal barriers (based on ecological and geographical dispersal suitability), we tested whether environmental predictive variables can discriminate NNFEF floristic groups, and built canonical models and variation partitioning to assess which variables contributed most to the floristic variation. Results Despite extensive overlap in predictive variables, Amazon and Atlantic Forest were the most differentiated among the nine NNFEF groups. Floristic variation along NNFEFs was mainly determined by environmental factors (54.1%), with topographic and edaphic variables, mainly topographic wetness index and pH respectively, representing the most important predictors followed by a combination of environmental factors and dispersal barriers (22.7%). The fraction of pure dispersal barriers also contributed significantly to our model (3.7%), especially considering the second canonical axis. Conclusions The high importance of soil and topographic variables indicates that the species have a relatively narrow niche driven by such factors, suggesting that conservation strategies should not be generalized for NNFEFs. In addition, dispersal barriers do not seem to have prevented floristic exchanges between most NNFEF groups, except in the Atlantic Forest.

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