The ambrosial mycobiota of Treptoplatypus oxyurus (Platypodidae)

Ambrosia beetles (Coleoptera: Curculionidae) form obligate nutritional symbioses with ambrosia fungi cultivated within their galleries. Among them, the pinhole borers (Platypodinae) are predominantly tropical, with only two representatives native to Europe. One of these, the rare and understudied Treptoplatypus oxyurus primarily colonizes Abies alba. We investigated its fungal symbionts using cultivation, morphological, molecular, and phylogenomic approaches. We identified three numerically dominant associates in prothorax containing mycangia: Candida schatavii, Magnusiomyces fungicola, and a novel member of Ophiostomatales, Wilhelmomyces oxyuri gen. et sp. nov., which was the most abundant and exhibited both leptographium-like and hyalorhinocladiella-like morphs. Additionally, two novel yeast species were isolated and described: Blastobotrys sasensis sp. nov. and Sugiyamaella casensis sp. nov., both belonging to Trichomonascaceae (Dipodascales). Multigene and genome-wide analyses confirmed the distinct taxonomic placement of all three new species. These findings reveal a previously undocumented fungal diversity tightly linked to a unique pinhole borer T. oxyurus, enriching our understanding of fungi occurring with conifer-colonizing beetles, and with ecological and biotechnological relevance.