Bryophyte communities in the Amazon forest are regulated by height on the host tree and site elevation

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Summary Community composition of epiphytic bryophyte communities, sampled systematically in nine localities across 2800 km from east to west of the Amazon forest, was mostly explained by their height zone along the vertical microenvironmental gradient from the base to the top of the host tree. Despite the lack of correlation between geographical distance and dissimilarity in species composition, communities within the same locality were significantly more similar than communities from different localities in all height zones, with the highest values of similarity found between outer canopy communities. While height zone on the host tree explained most of the variation in species composition at local scale, elevation and temperature were the variables most strongly related to species composition at a geographical scale. Using the concepts of meta/local community of the Neutral Theory of Biodiversity and Biogeography, we showed that establishment limitation was strongest at the extremes of the vertical gradient. We estimated that communities of the tree base and the outer canopy drew individuals from outside the habitat species pool at a rate of 0.28 and 0.22, respectively, in contrast with values between 0.55 and 0.76 of other height zones. Our results offered contrasting evidence for the hypothesis that species inhabiting the canopy have higher chances of engaging in long‐distance dispersal events. If the stronger establishment limitation at the extremes of the gradient is not compensated by facilitated dispersal compared to other zones, as our results suggest, communities on the base and on the outer canopy might be, through time, subjected to stronger selection. Synthesis. This study indicated that the community composition of epiphytic bryophytes in the Amazon is mainly regulated by environmental conditions, both at local and at geographical scales. Dispersal, although predominantly local, did not show geographical structure across the area.