Potential Distribution of Wild Chinese Giant Salamander (Andrias davidianus) in Zhejiang Province from Environmental DNA

The Chinese giant salamander (CGS, Andrias davidianus) is an endangered aquatic amphibian in China. Using environmental DNA (eDNA), this study aimed to monitor the spatial distribution of this species in Zhejiang Province, providing a scientific basis for species assessment, evaluation of reintroduction effectiveness, and non-invasive monitoring. Based on historical records of species presence, 18 representative water localities were selected for sampling. Among these localities, eDNA signals of the CGS were detected at nine. After excluding sampling sites affected by historical CGS releases and surrounding breeding farms, Jinzi Peak and Huyuan were inferred as candidate potentially natural stream habitats within the province. Additionally, eDNA monitoring was conducted at two release sites, Gutian Mountain and Banshanyuan, for two consecutive years. Results revealed lower detection rates in both areas in the second year of monitoring, potentially attributed to low survival rates, dispersal and disappearance, or sampling variability. A principal component analysis (PCA) of water quality factors (including parameters such as NH3-N, TN, TP, COD) revealed distinct geographic clustering of CGS-positive and CGS-negative sampling sites that corresponded to their separation in topographic space, suggesting that the measured physicochemical conditions may be associated with the CGS eDNA detection probability. This study demonstrates that eDNA is a feasible and efficient method for surveying CGS in Zhejiang Province. Further, it provides an efficient non-invasive monitoring approach for endangered amphibians, with broad application prospects.