Influence of plant species identity, phylogeny, and functional traits on twig-associated fungal communities

Plant-associated fungi are critical for plant health and ecosystem stability, yet the ecological drivers of twig-associated fungal communities remain less explored than those of other plant organs (e.g., roots and leaves). In this study, we investigated how host plant species identity, phylogenetic relatedness, and functional traits (growth form, deciduousness, and mycorrhizal type) structure twig-associated fungal communities in a common-garden experiment. We also compared twig and leaf fungal communities from the same experimental system to quantify organ effects. We sampled twigs from 123 monoculture plots representing 73 plant species in the MycoPhylo experimental field and characterized associated fungi using metabarcoding. Ascomycota dominated the dataset (74% of OTUs), followed by Basidiomycota (23%). Functional guild annotation indicated that putative plant pathogens accounted for 20.5% of the OTUs, followed by litter saprotrophs, lichenized fungi, and wood saprotrophs (∼10% each). Alpha diversity was primarily associated with host deciduousness, while growth form and mycorrhizal type showed weaker or non-significant effects. In contrast, community composition was significantly structured by deciduousness, growth form, mycorrhizal type, and host species identity, with additional phylogenetic signals. Compared with leaves, community composition, but not richness, differed significantly between organs. Together, these results show that host functional traits, particularly deciduousness, and host identity jointly shape twig fungal community assembly, while organ-specific habitat filtering strongly influences fungal composition.