Deterministic processes have limited impacts on foliar fungal endophyte communities along a savanna-forest successional gradient

Patterns and drivers of succession provide insight into the mechanisms that govern community assembly and are indicators of community resilience and stability but are still poorly understood in microbial communities. We assessed whether the successional trends of woody vegetation are mirrored by foliar fungal endophyte communities of three tree species that are abundant across the woody successional gradient using a total amplicon sequencing approach. Additionally, we test the relative contribution of host identity, abiotic predictors, biotic factors, and spatial distance between sites in predicting community composition and species richness of endophyte communities. Unlike the woody community, endophyte communities showed no consistent evidence of deterministic successional trends. Host identity was the most important factor structuring fungal endophyte community composition. Spatial distance played some role in explaining differences in community composition, but the effects of this and other environmental variables were small and not consistent between different host species. Much of the variation in endophyte composition remained unexplained. Host identity was most important in predicting endophyte richness. Although endophyte communities showed no deterministic succession, community assembly was most strongly influenced by host identity and spatial distance.