Metabarcoding of mycetangia from the species complex (Curculionidae: Scolytinae) reveals diverse and functionally redundant fungal assemblages.

-bark beetles are associated with microbes that can detoxify terpenes, degrade complex molecules, supplement and recycle nutrients, fix nitrogen, produce semiochemicals, and regulate ecological interactions between microbes. Females of some species harbor microbes in specialized organs called mycetangia; yet little is known about the microbial diversity contained in these structures. Here, we use metabarcoding to characterize mycetangial fungi from beetle species in the complex, and analyze variation in biodiversity of microbial assemblages between beetle species. Overall fungal diversity was represented by 4 phyla, 13 classes, 25 orders, 39 families, and 48 genera, including 33 filamentous fungi, and 15 yeasts. The most abundant genera were , , , , , , , , , and . Analysis of α-diversity indicated that fungal assemblages of . showed the highest richness and diversity, whereas those associated with . and . had the lowest richness and diversity, respectively. Analysis of β-diversity showed clear differentiation in the assemblages associated with . , . , and . , but not between closely related species, including . and . and . and . . A core mycobiome was not statistically identified; however, the genus was shared among seven beetle species. Interpretation of a tanglegram suggests evolutionary congruence between fungal assemblages and species of the . complex. The presence of different amplicon sequence variants (ASVs) of the same genus in assemblages from species of the . complex outlines the complexity of molecular networks, with the most complex assemblages identified from . , . , . , and . . Analysis of functional variation of fungal assemblages indicated multiple trophic groupings, symbiotroph/saprotroph guilds represented with the highest frequency (∼31% of identified genera). These findings improve our knowledge about the diversity of mycetangial communities in species of the . complex and suggest that minimal apparently specific assemblages are maintained and regulated within mycetangia.