Assembly of arbuscular mycorrhizal fungal communities changes from stochastic to deterministic during primary succession

On new land, succession of arbuscular mycorrhizal (AM) fungal communities depends on dispersal of propagules from a regional metacommunity and on supply of plant partners locally. We followed the succession of AM fungal communities from 2010 to 2016 on the artificial island Peberholm, which was constructed in 1998. We surveyed AM fungal communities using metabarcoding. Early in succession, AM fungal communities were characterized by a high proportion of sporulating taxa and strong dominance, consistent with a dispersal-driven mass effect imprinting the initial community composition. Over time, the prevalence of sporulating taxa declined, additional taxa were gained and beta-diversity at the whole-island level increased. This pattern suggest a gradual shift towards a more deterministic assembly, where biotic interactions and environmental filtering play a greater role, leading to higher spatial differentiation of AM communities in response to abiotic conditions and plant communities.