Bark and ambrosia beetles (Coleoptera: Scolytinae) associate with pathogenic fungi to colonise
new territories. Large scales forest pest and disease outbreaks are linked to this phenomenon,
which remains still poorly understood. To prevent or mitigate these outbreaks is crucial to
characterise beetle-fungi associations, understanding the underlying mechanisms behind these
interactions. However, studying fungal communities has been challenging due to the cryptic
nature and complex taxonomy of fungi. Thanks to molecular techniques like metabarcoding, it
is possible to unveil many previously unnoticed fungi. In the present work, I first compare two
widely used DNA markers (ITS and LSU) to evaluate their suitability for beetle-associated fungal
community characterization (Chapter 1). I then compare the fungal communities associated
with bark and ambrosia beetles on forests consisting of different host trees at the New Forest
National Park (Chapter 2). This way, I evaluate the effect of the host tree identity as a driver of
these fungal communities. Chapter 3 further takes this comparison at the regional level by
assessing the impact of different forest compositions from 20 sites across the UK, ranging from
monospecific conifers to mixed broadleaves. Finally, I used the same methodology to compare
the fungi from these native beetle communities with fungi harboured by the first UK-born
population of the invasive bark beetle Ips typographus. Results unveiled the potential invasive
fungal associates that this species could be vectoring into the United Kingdom. I also evaluated
the fungal communities harboured by Ips typographus specimens across different
developmental stages and host trees. Further implications of the present work are discussed in
Chapter 6. My research underlines the power of metabarcoding as a tool to better understand,
evaluate, and compare fungal communities with a wide range of fungal disease and forest
management-related implications.