Abstract: Human disturbances can drive the expansion of aggressive native plant species, which can significantly impact ecological communities. Investigating the effects of these species on ecological networks is crucial for biodiversity conservation and management. While previous research has shown that aggressive native plant can negatively affect aboveground pollination networks, their impacts on belowground ecological networks remain unexplored. To address this gap, we conduct field experiments to investigate the ecological impacts of an aggressive native plant, Euphorbia jolkinii Boissier (hereafter Euphorbia), on plant and arbuscular mycorrhizal fungi (AMF) communities, plant–AMF interactions, and mycorrhizal network structures in ten overgrazed subalpine meadows. Our findings indicate that Euphorbia exhibits a high level of generalization in its interactions with AMF. While Euphorbia did not significantly reduce the species richness of neighboring plants or AMF, it notably altered species composition and reduced plant biomass. Furthermore, Euphorbia also affected the interactions among species by altering plant composition and rewiring interactions. These changes led to plant–AMF networks influenced by Euphorbia exhibiting reduced connectance and nestedness but increased modularity. These discoveries underscore the considerable negative impacts of aggressive native plant species on belowground mycorrhizal networks and plant biomass. Our results highlight the necessity to develop effective management and restoration strategies for areas impacted by the expansion of aggressive native species.

Key words: aggressive native species, belowground mutualistic networks, ecosystem functioning, Euphorbia jolkinii Boissier, grassland degradation, plant-mycorrhizal interactions