Abstract (< 250 words)
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.