Testing the effectiveness of environmental DNA (eDNA) to quantify larval amphibian abundance

Abstract

Environmental DNA (eDNA) monitoring is rapidly becoming an established approach for detecting the presence of aquatic organisms and may also be useful for indexing or estimating species abundance. However, the link between eDNA concentration and abundance of individuals (i.e., density or biomass) remains tenuous and may vary widely across species and environmental conditions. We investigated the relationship between eDNA concentration and abundance in two common and closely related amphibians in eastern North America, the wood frog (Rana sylvatica), and northern leopard frog (R. pipiens). We manipulated tadpole density in 80-L mesocosms and documented the relationship between tadpole density and biomass and eDNA concentration through time. The two species differed in the amount of detectible genetic material produced, despite having comparable biomass. Concentration of eDNA increased with tadpole numbers and was primarily correlated with tadpole density in wood frogs and biomass in leopard frogs. eDNA degradation rates were rapid and comparable between species, with tadpoles becoming indetectable within 5 days post-removal from the mesocosm, irrespective of tadpole density. Overall, our findings support that eDNA concentration has potential for tracking amphibian abundance in wetlands, but that indices of abundance are likely to be coarse and speciesspecific calibration will be required. Future research should address how biotic and abiotic factors influence eDNA production, degradation, and recovery across species and through time before relying on eDNA for monitoring amphibian abundance in nature.

Comparative analysis of amphibian genomes: an emerging resource for basic and applied research

“…Additionally, well-annotated genomes can be used to create eDNA assays for population monitoring (Breton et al, 2022;Saeed et al, 2022).…”

“…The increased availability of amphibian genomes can also aid conservation efforts in this highly threatened group by facilitating research on genome-wide functional diversity, which can be used to inform management decisions such as genetic rescue or targeted genetic intervention for species threatened by habitat loss or chytridiomycosis (Chestnut et al, 2014; Kosch et al, 2022). Additionally, well-annotated genomes can be used to create eDNA assays for population monitoring (Breton et al, 2022; Saeed et al, 2022).…”

From roads to biobanks: Roadkill animals as a valuable source of genetic data

“…While not all animals cross roads or become roadkill, we know that many species are susceptible [40][41][42] and thus, this sampling approach can provide access to a large diversity of species. The resulting data could contribute to gain much needed understanding of existing biodiversity in less-studied areas and could be used in combination with other approaches such as environmental DNA (eDNA) and metabarcoding [43,44].…”