Environmental DNA (eDNA) and Field Surveys as Complementary Tools for the Biomonitoring of Amphibian Communities

Abstract

Amphibians are facing large population declines as a result of both natural and anthropogenic threats. Reconstructing and understanding the composition and structure of amphibian communities is essential for developing effective monitoring and conservation strategies. In this study, we compared environmental DNA metabarcoding (eDNA-MB) data with a comprehensive dataset obtained from acoustic and visual encounter surveys (AVES) in a set of Mediterranean ponds. Additionally, we designed and validated a quantitative PCR (qPCR) assay for the Iberian ribbed newt (Pleurodeles waltl) and tested its ability with eDNA-MB and AVES in assessing the presence and population densities of this species. Our findings provide evidence that eDNA-MB can be a valuable method for reconstructing the composition and structure of amphibian communities. eDNA-MB identified all expected amphibian species from the regional species pool, including some that were missed in traditional surveys. Although eDNA-MB abundance estimations for P. waltl seemed virtually independent of population densities obtained through field surveys, we found a significant association between eDNA concentration (qPCR) and AVES abundance estimates. Our findings suggest that effective strategies for amphibian biomonitoring need the combination of community data obtained from both traditional and eDNA surveys, especially in the Mediterranean region where strong environmental constraints can affect the detection and persistence of eDNA in freshwater ecosystems.