Poisonous weeds enhance soil bacterial adaptive potential to facilitate expansion

Poisonous weeds poses severe threats to ecosystem functions and services in grasslands. Soil microorganisms play crucial roles in mediating plant growth and adaptation, yet their responses to poisonous weeds and potential contributions to plant expansion via enhanced microbial adaptability remain elusive. We conducted a large-scale investigation spanning 3,000 km across grasslands dominated by Stellera chamaejasme, an iconic poisonous weed widely distributed in China, aiming to elucidate soil bacterial community assembly mechanisms, ecological and evolutionary attributes, and co-occurrence network traits, thereby revealing microbial environmental adaptive potential. Compared with control grasslands free of Stellera, Stellera-dominated grasslands exhibited significantly higher relative importance of stochastic processes in soil bacterial community assembly, accompanied by broader niche breadths, stronger phylogenetic conservatism, and more complex and stable co-occurrence networks. These results suggest that soil bacterial communities in Stellera-dominated grasslands possess enhanced adaptive capacity, potentially facilitating the colonization and expansion of poisonous weeds across heterogeneous habitats via positive plant-soil feedbacks. Our study provides new insights into the mechanisms underlying the expansion of poisonous weeds from the perspective of belowground microbial adaptive potential.