Tropical forest type influences community assembly processes in arbuscular mycorrhizal fungi

Aim Plant community assembly in tropical rain forest has been shown to be largely governed by stochastic processes, but as arbuscular mycorrhizal (AM) fungi display limited host preference, they may not follow the same stochastic assembly pattern. Here, we determined the relative importance of environmental and spatial drivers responsible for the community assembly process of AM fungi in two types of tropical rain forest: semideciduous rain forest and dense ombrophilous forests. Location Atlantic rain forest in north-eastern Brazil, South America. Taxon Arbuscular mycorrhizal fungi (Glomeromycotina). Methods We collected root samples from eight protected areas of Atlantic forest along a 700 km transect in north-eastern Brazil. We measured the relative importance of deterministic and stochastic processes by redundancy analysis (RDA) and variation partitioning in comparison with null expectations using ad hoc generated neutral communities. Furthermore, we accessed species associations from co-occurrence data, at different scales using a Bayesian approach of Hierarchical Modelling of Species Communities. Results Overall, the extent to which stochastic and deterministic processes affected community assembly depended on the forest type and the spatial scale. Specifically, we found that abiotic and biotic predictors of AM fungal community assemblages are related to environmental homogeneity in tropical rain forests. Main conclusions The results of the study show that dynamics in community assembly was clearly different between the two forest types, and that the difference most likely is due to differences in responses to environmental variables.