Within-species Plant Phylogeny Drives Ectomycorrhizal Fungal Community Composition in Tree Roots along a Timberline

Fungal community structure in tree roots and in surrounding soils is constrained significantly by plant phylogenetic relationships among multiple species. However, whether plant phylogenetic relationships within a single species can mediate fungal community structure has not been investigated. Here, we surveyed ectomycorrhizal (EcM) and saprotrophic (SAP) fungal community structure in fine roots and in neighboring soils of Betula ermanii along the Changbai Mountain timberline. When accounting for the effects of soil properties, root traits, and geographic distance, within-species plant phylogeny was the sole driver of EcM fungal community composition in roots, whereas geographic distance was the strongest driver of SAP fungal community composition in soils and roots. Deterministic processes were dominant in root EcM fungal community assembly, and stochastic processes were dominant in SAP fungal community assembly. Overall, the findings demonstrate that within-species plant phylogeny drives EcM fungal community composition in roots, and fungal community assembly is both guild- and habitat-dependent.