Bark beetles are fundamental drivers of forest ecosystem dynamics. However, some species
within this group have recently also emerged as significant pests in environments
managed by humans, including nurseries, orchards, and urban areas. Specifically, certain
Scolytus species pose potential economic and ecological threats to stone fruit cultivation
across the Mediterranean basin. Although the role of the mycobiome in mediating bark
beetle-host interactions has been well documented for many forest models, the symbiotic
associations between beetles and fungi in cultivated Mediterranean agroecosystems
remain poorly understood. This study provides the first comprehensive characterization
of the fungal community associated with the almond bark beetle Scolytus amygdali in
southern Mediterranean almond orchards. Integrating culture-dependent isolations with
culture-independent approaches, i.e., high-throughput sequencing, allowed us to assess
the beetle mycobiome across beetle adults, gallery systems, and associated necrotic
wood lesions. Molecular characterization revealed Geosmithia, Paecilomyces, and Quambalaria
to be the dominant taxa within the S. amygdali mycobiome. Their frequent occurrence
suggests that they may be recurrent associates in the gallery environment, although
their functional roles remain unclear. Furthermore, metabarcoding analyses provided
additional novel insights into the beetle mycobiome, identifying Candida and Yamadazyma
yeasts as potential core constituents of the gut microbiome. Future research should
prioritize elucidating the role of these putative fungal symbionts for the beetles,
particularly the pathogenic potential on almonds, and the functional efficiency of
S. amygdali as a vector. Overall, our findings elucidate the complex taxonomic diversity
of these associations. Moreover, obtained results provide a foundational ecological
framework to better understand to what extent these associations can threaten host
plants and to develop future sustainable management strategies in managed ecosystems.
