Abundant and rare fungal taxa exhibit different patterns of phylogenetic niche conservatism and community assembly across a geographical and environmental gradient

Fungi play critical roles in the regulation of terrestrial ecosystem processes and functions. However, the biogeographic patterns, assembly mechanism and phylogenetic information of fungi across complex environmental gradients remains unexplored, especially the differences between abundant and rare fungi. Here, based on an extensive soil sampling (117 samples) covering almost all vegetation types in the Loess Plateau, we explored biogeography, community assembly, and phylogenetic niche conservatism of abundant and rare fungi. The results showed that the abundant fungal taxa exhibited less phylogenetic clustering than the rare fungi, but their environmental associations and phylogenetic signals were stronger. Stochastic processes dominated the assembly of abundant fungi. In contrast, the homogeneous selection of deterministic processes was the major assembly process of rare taxa. Soil organic carbon and nitrate nitrogen were the key factors driving the community assembly of abundant and rare fungi, respectively. Microbial network and niche analyses further indicated abundant fungi were more advantageous for maintaining microbial co-occurrence patterns and metabolic flexibility. We concluded that abundant fungi have broader environmental adaptation potential at spatially complex environmental scales and are less dispersed by environmental changes. These results provide insights for understanding the phylogenetic and community assembly mechanisms by which fungi adapt to large-scale environmental changes.