Structural diversity across arbuscular mycorrhizal, ectomycorrhizal, and endophytic plant-fungus networks

Abstract

BackgroundBelow-ground linkage between plant and fungal communities is one of the major drivers of terrestrial ecosystem dynamics. However, we still have limited knowledge of how such plant-fungus associations vary in their community-scale properties depending on fungal functional groups and geographic locations.\n\nMethodsBased on high-throughput sequencing of root-associated fungi in eight forests along the Japanese Archipelago, we performed a comparative analysis of arbuscular mycorrhizal, ectomycorrhizal, and saprotrophic/endophytic associations across a latitudinal gradient from cool-temperate to subtropical regions.\n\nResultsIn most of the plant-fungus networks analyzed, host-symbiont associations were significantly specialized but lacked \"nested\" architecture, which has been commonly reported in plant-pollinator and plant-seed disperser networks. Meanwhile, the structure of arbuscular mycorrhizal networks was differentiated from that of ectomycorrhizal and saprotrophic/endophytic networks, characterized by high connectance. Our data also suggested that geographic factors affected the organization of plant-fungus network structure. For example, the southernmost subtropical site analyzed in this study displayed lower network-level specificity of host-symbiont associations and higher (but still low) nestedness than northern localities.\n\nConclusionsOur comparative analyses suggest that arbuscular mycorrhizal, ectomycorrhizal, and saprotrophic/endophytic plant-fungus associations often lack nested network architecture, while those associations can vary, to some extent, in their community-scale properties along a latitudinal gradient. Overall, this study provides a basis for future studies that will examine how different types of plant-fungus associations collectively structure terrestrial ecosystems.