ABSTRACT Accurate information on species abundances and their distribution in space is key to ecological research and essential for informed decision‐making in environmental management. Environmental DNA (eDNA) allows community‐wide detection of biodiversity, but its limited ability to estimate species abundance from metabarcoding outputs poses important challenges for its broader application. The eDNA Integrating Transport and Hydrology (eDITH) framework addresses some of these limitations by partly accounting for eDNA transport and decay dynamics in river networks and allows predicting the spatial distribution of taxa at high resolution. However, its capability for providing quantitative estimates of taxon abundances has so far not been empirically validated. Here, we utilized spatially replicated eDNA and kick‐net samples collected in spring and summer at 25 sites along a 126 km 2 river catchment. We contrasted species‐level relative abundances of insect communities obtained via eDNA metabarcoding read counts and via eDITH estimates with those obtained from the kick‐net samples. We found that eDNA read counts of sampled locations did not correlate with the associated local kick‐net (i.e., realized) insect abundance, but that the eDITH estimates did. However, results varied across insect orders and the improvements provided by eDITH were highly species‐specific. Our findings corroborate the inadequacy of utilizing raw read counts for quantitative inference and pose forward the potential of the eDITH framework in circumventing some of the limitations of metabarcoding outputs. Together with other recently proposed correction approaches, this framework contributes to ongoing efforts to refine the interpretability of metabarcoding data. As the demand for quantitative biodiversity data continues to grow in both ecological research and environmental management, refining and validating sampling approaches remains a critical priority.
Cereghetti et al. (Thu,) studied this question.