Past spatial structure of plant communities determines arbuscular mycorrhizal fungal community assembly

Due to the importance of arbuscular mycorrhizal fungi (AMF) in ecosystem pro-ductivity, a key ecological question is how do their communities assemble? As plant spatial patterns constitute a mosaic of AM fungi habitats, we hypothesized that AM fungal community assembly is determined by plant community structure, both in space and time.We tested our hypothesis by sampling individuals of two host-plant species, Brachypodium pinnatum and Elytrigia repens, from experimental communities cultivated in mesocosms, and assessed their AM fungal root colonizers by mass sequencing. We related AM fungal community structure to the distribution of neighbouring plant species at different spatio-temporal scales.We demonstrated that AM fungal community assembly depends mostly on past plant spatial patterns at a small spatial scale (5 cm), indicating that plants growing at given locations leave a footprint on the AM fungi community. This spatial scale of response was also influenced by the host-plant species, probably by its clonal propagation.Synthesis. Overall, we highlighted that processes involved in Arbuscular mycor-rhizal (AM) fungal community assembly do not operate at the rough scale of the overall plant community mosaic but are instead locally determined, delineating the AM fungal ‘eye-view’ of the host-plant community.