Host Identity Determines the Bacterial and Fungal Community and Network Structures in the Phyllosphere of Plant Species in a Temperate Steppe

Elucidating the plant-microbiome network is of importance in understanding species coexistence in natural ecosystems. The phyllosphere, which is the aerial parts of terrestrial plants, is inhabited by diverse microbes. However, few studies have focused on the phyllosphere microbiome and plant-microbiome network in temperate grasslands. In this study, we explored the diversity, community structure, and network architecture of phyllosphere bacteria and fungi in 19 plant species native to the temperate grassland in Inner Mongolia, China. We obtained 3,313 and 758 phyllosphere bacterial and fungal operational taxonomic units, respectively, and found that the bacterial community was dominated by Proteobacteria, Actinobacteriota, and Firmicutes, whereas the fungal community was dominated by Ascomycota and Basidiomycota. Plant identity exerted significant impacts on alpha-diversities of both bacterial and fungal communities. The composition of bacterial and fungal communities differed among plant species. Plant identity had a greater effect on fungal than bacterial communities. Both bacterial and fungal network structures were characterized by specialized, modular, lowly connected, and no nested properties. The plant-fungal network had a high level of specification, modularity, antinestedness, and connectance compared with the plant-bacterial network. Our results suggest more intimate relationships between plants and phyllosphere fungi than between plants and phyllosphere bacteria and also that the phyllosphere fungal community in the temperate grassland ecosystem is more resistant to environmental disturbance than the phyllosphere bacterial community. These findings may contribute to our understanding of the mechanisms by which species coexist and communities stabilize in grassland ecosystems.