Rhizosphere bacterial characteristics reveal the invasive advantage of Sphagneticola trilobata compared to the greening grass Axonopus compressus

Biological invasions pose a major threat to ecosystem stability, yet the role of rhizosphere microbiomes in conferring competitive advantages to invasive plants remains insufficiently understood. In particular, whether invasive plants outperform resident or naturalized species by assembling distinct and functionally advantageous bacterial communities is still unclear. We hypothesized that the invasive plant Sphagneticola trilobata gains a competitive advantage by selectively recruiting beneficial rhizosphere bacteria, whereas the long-naturalized greening grass Axonopus compressus may experience negative soil legacy effects. Based on 16 S rRNA gene sequencing across 15 paired field sites, we found that S. trilobata assembled a significantly more diverse, even, and structurally distinct rhizosphere bacterial community than A. compressus. The rhizosphere of S. trilobata was enriched with key bacterial taxa, including Rhizobiales, Cytophagales, Pseudomonadaceae, Comamonadaceae, Streptomyces and Novosphingobium, which are associated with nitrogen cycling, organic matter degradation, plant growth promotion, and allelochemical detoxification. Co-occurrence network analysis showed that the S. trilobata rhizosphere exhibited a more complex microbial network with a higher proportion of positive correlations. Functional prediction suggested an increased potential for carbohydrate transport and metabolism in the rhizosphere of the invasive plant. In addition, inoculation with a synthetic community (SynCom) composed of bacterial strains predominantly detected in the rhizosphere of S. trilobata significantly increased plant biomass and root allocation under nutrient-limited conditions. These results demonstrate that S. trilobata actively engineers a specialized and functionally robust rhizosphere microbiome that directly enhances its growth and resource-use strategy. This host-mediated microbiome assembly provides a microbial mechanism underlying the competitive dominance and invasion success of S. trilobata, highlighting the critical role of belowground bacterial communities in plant invasion processes.