Abstract
Environmental 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 41 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 taxonomic 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 taxonomic 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 regional scales can better predict phylogenetic and taxonomic turnover than geomorphology and soils.
Highlights
The longstanding debate concerning the role of ecological interactions and environmental filters vs. neutral processes as mechanisms explaining tree community assembly in Communicated by Marie-Josée Fortin.Amazon forests is a prominent topic in ecological and evolutionary research (Tuomisto et al 2002; ter Steege et al 2006; Kraft et al 2011; Swenson et al 2013; Baker et al 2014; Pos et al 2019)
The results of the distance-based redundancy analysis (db-Redundancy Analysis (RDA)) showed that 36% of variation in phylogenetic turnover was explained by the constrained axis 1 of the ordination, the second constrained axis explained 18% of the total variation in phylogenetic composition
We found evidence for high taxonomic turnover with variation in soils and geomorphology at all spatial scales the effect of this relationship was not significant to explain patterns of phylogenetic turnover at broad spatial scales (Table 3A)
Summary
The longstanding debate concerning the role of ecological interactions and environmental filters vs. neutral processes as mechanisms explaining tree community assembly in Communicated by Marie-Josée Fortin.Amazon forests is a prominent topic in ecological and evolutionary research (Tuomisto et al 2002; ter Steege et al 2006; Kraft et al 2011; Swenson et al 2013; Baker et al 2014; Pos et al 2019). Describing and analysing the patterns of species and lineage composition across spatial and environmental gradients is fundamental to understand the mechanistic causes that promote community assembly of this hyper-diverse ecosystem Both climate and soils are major environmental filters for Amazonian plant communities and are likely drivers of taxonomic turnover and phylogenetic beta diversity patterns among tree communities across the region (Antonelli et al 2009; Fine and Kembel 2011; Honorio Coronado et al 2015; Baldeck et al 2016; ter Steege et al 2006). Few studies have evaluated the combined effect of geology, soil nutrient availability, regional climatic variables and dispersal limitation on the patterns of phylogenetic beta diversity of Amazon tree communities Such a comprehensive approach would allow us to investigate the historical and evolutionary processes that underlie the patterns of phylogenetic composition among tree communities at regional scales (Fine and Kembel 2011)
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