Lower specificity of mycorrhizal associations in the invader Nicotiana glauca could mediate adaptive advantages over the native plant species during the drought season

Mycorrhizal associations involving arbuscular mycorrhizal fungi (AMF) can play a critical role in the success of plant invasion processes, particularly under environmental stress conditions such as drought. This study investigated the effects of plant invasiveness, seasonal soil moisture (wet vs. dry seasons), and characteristics of invaded sites on AMF communities associated with the roots of the invasive species Nicotiana glauca and co-occurring native plants in Mediterranean semiarid ecosystems. High-throughput MiSeq sequencing identified 546 amplicon sequence variants (ASVs) of AMF, with members of the family Glomeraceae predominating in all samples. Native plants exhibited significantly greater AMF richness (the Chao1 richness estimator ranged from 21.8 under wet conditions to 40.4 under dry conditions) and diversity (the Shannon-Weaver diversity index ranged from 2.4 under wet conditions to 2.9 under dry conditions), whereas the AMF communities associated with N. glauca were less diverse and characterized by generalist taxa independently soil moisture (the Shannon-Weaver diversity index ranged from 2.0 under wet conditions to 2.1 under dry conditions). The rhizosphere of invasive plants exhibited higher enzymatic activities-including dehydrogenase, urease, and alkaline phosphomonoesterase (approximately 70 %, 33 %, and 26 % higher, respectively, than those in the rhizosphere of native plants)-with enzyme values remaining more stable across seasons. Canonical correspondence analysis (CCA) revealed that the AMF community composition was influenced by soil biochemical parameters, particularly the alkaline phosphomonoesterase activity related to phosphorus cycling. Moreover, rhizospheric soils of N. glauca displayed greater structural stability, especially during the dry season. These findings indicate that N. glauca supports resilient and functionally efficient AMF associations under varying water availability, which may enhance its ecological success in drought-affected environments.