Abstract
We analyzed the most extensive data set of tree inventory plots spread over the complete Amazon basin and Guiana shield. We aimed to separate the regional and local tree alpha-diversity to investigate the drivers of diversity at the relevant scale. Our results are consistent with the partitioning of total tree alpha-diversity into regional and local components, which are controlled by evolutionary- and ecological processes, respectively. Regional diversity is correlated with palaeo-climatic stability (31%), and long-term large-scale ecosystem dynamics (14%), as represented by the age of the geological formation. Both mechanisms contribute to high diversity in the central to western Amazon. Actual rainfall seasonality is correlated with regional tree diversity to a certain extent (19%), but we argue that this is of little consequence for the evolutionary drivers of the regional species pool. Frequency of disturbance is the main process driving local diversity, although its explanatory power is relatively small (17%)