A Reference DNA Barcode Library for UK Fungi associated with Bark and Ambrosia Beetles.

Bark and ambrosia beetles are ecologically important and widespread forest organisms. While flying between host plants and tunnelling into bark, they vector a high diversity of plant and insect-associated fungi within and between forests. These fungal communities live under the bark and rarely produce visible spore-bearing structures, making them difficult to sample and identify at scale. By combining passive insect trapping across the United Kingdom with individual beetle metabarcoding, we generated a reference DNA barcode library for fungi associated with over 1000 beetles, representing 25 native weevil species in the subfamily Scolytinae (Curculionidae). Sampling sites span longitudinal and latitudinal gradients, multiple forest types, and both natural and plantation forests. We use state-of-the-art fungal ITS2 OTU clustering and identification, resulting in 5274 identified fungal OTUs. This fungal diversity data can be used alongside extensive site and sample metadata to explore geographic and ecological biodiversity patterns. As these associations can be highly invasive and damaging, this resource provides a baseline to understand current fungal communities and monitor future changes.