Background: Wetlands in Neotropics harbor high fungal diversity, including arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE). This study describes the interaction of plant roots with AMF and DSE in a freshwater wetland belonging to a hotspot of biodiversity.Hypothesis: Differential root colonization between arbuscular mycorrhizal and dark septate endophyte fungi is influenced by plant species and abiotic conditions in a freshwater wetland.  Studied species: Plant species colonized by arbuscular mycorrhizal and dark septate endophyte fungi.Methods: Properties of soils and the water column, floristic composition, root colonization by AMF and DSE, and molecular identification of AMF inside roots were studied.Results: Soils were Gleysol and flooded during the rainy season. Most of identified plant species were herbaceous, with Cyperus articulatus and Mimosa pigra as the dominant species. Seven of 8 analyzed plant species exhibited differential co-colonization between AMF and DSE. Repeated sampling for one year under flooding/dry conditions demonstrated that C. articulatus and M. pigra were mainly associated with DSE and AMF, respectively. A positive correlation between dissolved O2 in the water column and fungal colonization was observed in C. articulatus. Glomerales and Archaeosporales were molecularly identified inside roots containing arbuscules of M. pigra.Conclusions: Findings highlight differential coexistence between AMF and DSE in plant roots; fungal colonization was influenced by flooding/dry conditions in a neotropical wetland; the community of AMF inside arbusculated roots of M. pigra includes at least four clades.

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