The contribution of environmental and dispersal filters on beta diversity patterns in Amazonian tree communities

Environmental filters (e.g. climate, geomorphology and soils) and
dispersal filters are key determinants of species distributions of
Amazonian tree communities. However, a comprehensive analysis of the role
of environmental and dispersal filters is needed to understand the
ecological and evolutionary processes that drive phylogenetic and
taxonomic turnover of Amazonian tree communities. We compare measures of
taxonomic and phylogenetic beta diversity in 40 one-hectare plots to test
the relative importance of climate, soils, geology, geomorphology, pure
spatial variables and the spatial variation of environmental drivers of
phylogenetic and taxonomic turnover in Ecuadorian Amazon tree communities.
We found low phylogenetic and high taxonomic turnover with respect to
environmental and dispersal filters. In addition, our results suggest that
climate is a significantly better predictor of phylogenetic turnover and
species turnover than geomorphology and soils at all spatial scales. The
influence of climate as a predictor of phylogenetic turnover was stronger
at broader spatial scales (50 km2) whereas geomorphology and soils appear
to be better predictors of taxonomic turnover at mid (5 km2) and fine
spatial scales (0.5 km2) but a weak predictor of phylogenetic turnover at
broad spatial scales. We also found that the combined effect of
geomorphology and soils was significantly higher for species turnover at
all spatial scales but not for phylogenetic turnover at large spatial
scales. Geographic distances as proxy of dispersal limitation was a better
predictor of phylogenetic turnover at distances of 50<500 km. Our
findings suggest that climatic variation at local and regional scales can
better predict phylogenetic and taxonomic turnover than geomorphology and
soils.