Dispersal assembly of rain forest tree communities across the Amazon basin

Significance The Amazon is largely covered by contiguous rain forest. Nevertheless, previous studies have suggested that past geological and climatic events, as well as limited seed dispersal, may have restricted the movement of tree lineages across the Amazon. Using a phylogenetic approach, we show that dispersal into local communities and larger regions in the Amazon appears to not have been limited on evolutionary timescales, but instead, local communities have been assembled by lineages from across the Amazon. These results contrast with those from seasonally dry tropical forests, where closely related species are clustered in geographic space. Furthermore, our results suggest a role for dispersal as an initiator for geographic isolation that might lead to speciation in Amazonian trees.