Environmental DNA (eDNA) analysis is a promising tool for non-disruptive
and cost-efficient estimation of species abundance. However, its
practical applicability in natural environments is limited because it is
unclear whether eDNA concentrations actually represent species abundance
in the field. Although the importance of accounting for eDNA dynamics,
such as transport and degradation, has been discussed, the influences of
eDNA characteristics, including production source and state, and
methodology, including collection and quantification strategy and
abundance metrics, on the accuracy of eDNA-based abundance estimation
were entirely overlooked. We conducted a meta-analysis using 56 previous
eDNA literature and investigated the relationships between the accuracy
(R2) of eDNA-based abundance estimation and eDNA characteristics and
methodology. Our meta-regression analysis found that R2 values were
significantly lower for crustaceans than fish, suggesting that less
frequent eDNA production owing to their external morphology and
physiology may impede accurate estimation of their abundance via eDNA.
Moreover, R2 values were positively associated with filter pore size,
indicating that selective collection of larger-sized eDNA, which is
typically fresher, could improve the estimation accuracy of species
abundance. Furthermore, R2 values were significantly lower for natural
than laboratory conditions, while there was no difference in the
estimation accuracy among natural environments. Our findings shed a new
light on the importance of what characteristics of eDNA should be
targeted for more accurate estimation of species abundance. Further
empirical studies are required to validate our findings and fully
elucidate the relationship between eDNA characteristics and eDNA-based
abundance estimation.
Environmental DNA analysis of invasive aquatic plant, Egeria densa in the Oota River, Japan.
