Introduction
Amphibians are vertebrates with life cycles that crucially depend on
both aquatic and terrestrial habitats. They play an important
intermediate position in food chains and ecosystems, and are important
indicator taxa of environmental health (Li et al., 2017). Amphibians are
not only an important component of biodiversity but are also a taxonomic
group that has undergone significant changes in taxonomical organization
in recent years and is experiencing rapid population declines and risks
of extinction at a global scale (Gao et al., 2022). China is among the
countries with the richest biodiversity in the world and specifically
boasts the highest diversity of amphibian species(Xu et al.,2018).
Monitoring the status of this diverse fauna is often challenging.
According to the Technical Provisions on Survey and Assessment of
Amphibian and Reptile Diversity in County Areas (Ministry of Ecology
and Environment Announcement No. 84, 2017), traditional methods to
investigate amphibian diversity include traditional line transect
methods, trap-barrier systems, methods using artificial covers or
shelters, mark-recapture, call counting, and others. Traditional
investigation is often accurate and intuitive, but efficiency is
frequently affected by species, life stages and environmental conditions
(Ruppert et al., 2022). Moreover, a high level of taxonomic knowledge is
required of the traditional investigator, especially for identification
of eggs and larvae (Hopkins & Freckleton, 2002; S. Zhang et al., 2020).
In recent years, there has been increasing use of the environmental DNA
(eDNA) method, which allows the DNA of target organisms obtained from
environmental samples (e.g. water, soil, excrement, ancient sediments,
etc.) to be used for detection of presence or absence of the species,
and even enables inferences about their numbers and biomass (Ficetola et
al., 2019; Thomsen & Willerslev, 2015). Extensive use of eDNA
technology has been made for biodiversity surveillance across diverse
taxa, encompassing fish (Deiner et al., 2017; Jerde et al., 2011; P. F.
Thomsen, J. Kielgast, L. L. Iversen, P. R. Moller, et al., 2012),
amphibians (Goldberg et al., 2018; Pilliod et al., 2013; Strickler et
al., 2015; Valentini et al., 2016), benthic fauna (Cowart et al., 2018;
Laroche et al., 2018; Stoeck et al., 2018), plants (Johnson et al.,
2019; Johnson et al., 2021; Kodama et al., 2022), bacteria (Laroche et
al., 2018; Stoeck et al., 2018; Y. Zhang et al., 2020), and
microorganisms (Handelsman, 2004; Rondon et al., 2000). Nonetheless,
varied applications of eDNA technology among distinct biological cohorts
elicit discernible disparities. This review provides an exposition of
the applications of eDNA technology in amphibian monitoring and also
discusses the multifaceted factors determining its efficacy and
reliability. We also examine future research and questions that will
need to be addressed for the further development of eDNA technology for
amphibian population investigations.