Combining environmental DNA data and taxonomic surveys provides an unprecedented understanding of lichen diversity and accelerates the discovery of new species

Sequencing of environmental DNA is increasingly used to estimate biodiversity at various taxonomic and spatial levels. However, most such studies tend to deal with abstract numbers not linked to species names, which hampers evaluation and downstream use of the results. In our survey of epiphytic lichens in the Czech Republic, we managed to link sequences from environmental DNA with species names, using an existing reference database of DNA barcodes. On 1-ha sites in various types of central-European forests, we were able to compare DNA data from environmental samples with (i) results of a parallel taxonomic survey and (ii) species abundance data on a country-wide scale. In the environmental DNA data, we detected a large number of species strongly under-recorded in taxonomic surveys and in previous distributional data from the Czech Republic. Most of these species are either very small or poorly known microlichens notoriously overlooked by taxonomists. Some are rare species with specific ecological requirements, but many are relatively abundant. Numerous species apparently new to science were detected, of which 12 species and two genera are newly described here: Allarthothelium endochlorum, Atrodiscus fagicola (new genus), Bacidina omnicola, Biatorella ligni-putridi, Cryptodiscus neglectus, Gyalidea gabretae, Karstenia dryina, Micarea lobarica, Monilibrachium splendens (new genus), Psoroglaena neglecta, Toniniopsis pruinosa and Xylopsora diffissa. In the descriptions, eDNA data are, for the first time in lichenology, utilized for characterizing ecology and distribution of the new species. In addition, 43 species detected by eDNA are new to the Czech Republic (23 of them confirmed by the parallel taxonomic survey). Absconditella amabilis and Chaenotheca nitidula are new to Europe.