Aerial eDNA contributes vital information for fungal biodiversity assessment

Fungal diversity drives key processes in terrestrial ecosystems, but remains challenging to measure in the field and to monitor over time. Environmental DNA (eDNA) could provide insights into this diversity, once its validity to capture fungal assemblage properties is established. Using three approaches (full-season eDNA monitoring from air, snapshot visual surveys, and eDNA from wood), we present the first comparative forest scale fungal diversity assessment. The special focus was on two well-known fungal groups (lichens and wood basidiomycetes) in old hemiboreal forests. Most importantly, aerial eDNA revealed regional-scale cryptic diversity not detected in visual surveys, including species of conservation concern. However, at the local population scale, both eDNA approaches often missed visually detected species. The methods differed in detecting the spatial covariance of wood fungal and lichen diversity, with the combined (most complete) dataset indicating the strongest congruence. The results imply a fungal monitoring scheme that (a) maximizes field expert time for detecting conservation values; (b) uses aerial sampling to represent a broad range of ecosystems; (c) includes sites where both methods are used simultaneously in the same season; and (d) establishes permanent test sites for methodological development to exhaustively describe fungal diversity including within-species genetic diversity.