The effects of tree diversity and neighborhood on phyllosphere fungal communities

Phyllosphere fungi, encompassing both epiphytic and endophytic fungi, have rarely been studied along gradients of host diversity. In this study, we used a tree biodiversity experiment to investigate how tree species richness, host and neighboring species identities, and host-mycorrhizal association affect the richness and composition of the whole phyllosphere community as well as that considering epiphytes and endophytes separately. To distinguish epiphytes from endophytes, we employed a leaf-surface sterilization treatment. Richness and composition of the mycobiome were quantified using next-generation amplicon sequencing. Our findings revealed that tree species richness affected only the overall phyllosphere fungal community, not endophytes alone, suggesting that neighborhood effects predominantly influence fungi on the leaf cuticle. Neighborhood effects were only detectable in the phyllosphere as a whole and not within endophyte and epiphyte communities. Fungal community composition was shaped by host species identity, tree richness, host mycorrhizal type and the combination of mycorrhizal types at the plot level. This study underlines the importance of analyzing epiphytes and endophytes separately and highlights the necessity of using leaf-surface sterilization when examining phyllosphere fungal communities.