Plant invasions severely threaten the stability and biodiversity of fragile ecosystems in karst areas. Elucidating the microbial mechanisms underlying the interactions between invasive plants and native plants in rhizosphere soil is crucial for preventing plant invasions. In this study, high-throughput sequencing was used to compare the differences in rhizosphere fungi between two invasive and native plants in the Guizhou karst region. These findings provide theoretical support for understanding the ecological impact of invasive plants and for developing ecological management strategies based on soil microorganisms. The results revealed the following: (1) A total of 16 soil samples were included in the study, which comprised 1 phylum, 50 classes, 112 orders, 245 families, 463 genera and 629 species. (2) No significant differences were observed in the Ace, Chao, Shannon, Simpson and Sobs indices of the rhizosphere fungal communities between invasive plants and native plants (p > 0.05). (3) At the phylum level, no significant difference was observed in the community compositions of invasive and native plants; the dominant phyla were Ascomycota, Mortierellomycota and Basidiomycota; at the genus level, there were significant differences in the community composition of invasive and native plants, and the relative abundances of Minimedusa, Monocillium and Gymnopus in the rhizosphere soil of invasive plants were significantly higher (p < 0.05). (4) Functional predictions based on FUNGuild indicated a higher relative abundance of saprotrophic fungi associated with invasive plants. Community assembly processes for both invasive and native plants were primarily governed by stochastic ecological processes (e.g., drift). These findings suggest that plant invasion is associated with shifts in the composition and potential ecological functions of rhizosphere fungal communities in the karst area.

Alternanthera philoxeroides is a highly invasive alien species in China that causes waterway blockages, agricultural yield loss, biodiversity decline, and ecosystem degradation. This study assessed the invasion risk and environmental drivers of A. philoxeroides in Guizhou Province, a karst mountainous region in Southwest China. Occurrence records were obtained from field surveys and the Chinese Virtual Herbarium. The genetic algorithm for rule-set production (GARP) model and the jackknife method were employed to identify 13 key environmental indicators for predicting invasion risk. The global invasion risk index (GIRI) was applied to quantify the overall invasion risk. Additionally, the Geodetector model was utilized to analyze the spatially differentiated effects of six environmental factors. The results showed that A. philoxeroides poses a high invasion risk in Guizhou Province, and the invasion risk in the Yangtze River Basin within Guizhou is higher than that in the Pearl River Basin. The environmental factors influencing invasion risk, in order of impact, were slope, elevation, land use, river density, rocky desertification, and soil pH. Moreover, interactions among these factors further amplify the invasion risk. These findings provide valuable insights for developing targeted management strategies for A. philoxeroides in karst mountainous regions and support biodiversity preservation and regional ecological sustainability.