Neighbor-referenced mycorrhizal diagnostics for endangered tree conservation

This is the authors' abstract. We don't add key points for this paper.

Mycorrhizal fungi are increasingly recognized as crucial for conserving endangered tree species, yet practical guidance to determine whether mycorrhizal interventions (e.g., fungal inoculation) are necessary remains lacking. Here, we propose a neighbor-referenced diagnostic framework based on two key criteria: (i) whether endangered plants exhibit reduced mycorrhizal fungal diversity or simplified co-occurrence networks relative to neighboring plants, indicating a mycorrhizal deficit; and (ii) whether endangered plants harbor distinct mycorrhizal communities with limited overlap with neighboring plants, potentially restricting their access to local mycelial networks. We applied this framework to four endangered tree species in subtropical China, analyzing 636 root samples. Our results showed that reduced fungal diversity or simplified network structures relative to co-occurring plants were detected in only a few, but not all, endangered tree species, suggesting context-dependent rather than universal mycorrhizal constraints. Furthermore, differences in fungal communities between endangered trees and neighboring plants were not strong, with 22.5–50.6% of fungal ASVs shared at the neighborhood scale and 54.7–90.1% at the regional scale. These findings suggest that endangered trees often retain access to locally available mycorrhizal fungal pools, which may support recruitment after translocation and persistence after disturbance, underscoring the importance of conserving habitat matrices that maintain intact mycelial networks. Our diagnostic framework sheds light on developing evidence-based recovery strategies to enhance conservation efficacy for endangered plants.