1 Introduction of eDNA method

Due to the intensification of human activities and increased interference with the natural environment, the continuous decline of global biodiversity has become one of the major challenges in the 21st century (Butchart et al., 2010). Rapid, sensitive and accurate biodiversity survey tools are required to measure fluctuations in species diversity and abundance to inform conservation and management strategies (Kelly et al., 2014). Environmental DNA is DNA that can be extracted from environmental samples (such as soil, water or air) without prior isolation of any target organisms (Lodge et al., 2012; Taberlet et al., 2012). Environmental DNA analysis is divided into two main categories: single species identification and eDNA metabarcoding. Single species identification is mainly used for sensitive detection of rare and endangered animals and invasive non-native species in the context of environmental and species richness surveys (Wilcox et al., 2013). eDNA metabarcoding refers to analysis of eDNA with high-throughput sequencing technology, processing eDNA from water, soil and air by PCR amplification to determine the presence of species and perform biodiversity assessment (Ruppert et al., 2019). Compared with traditional survey methods, the eDNA metabarcoding technique provides outstanding species recognition. It can be used even if the investigators lack extensive abilities to classify species. Further, the use of eDNA does not require sampling approaches that are destructive or invasive to the environment or the biological community, nor does it require special equipment or particular observation times to detect those species that are difficult to observe due to small size or numbers (Deiner et al., 2017). Therefore, this technology has been widely used in the field of ecology.