Heatmap of relative abundances of the most important metabolic pathways inferred by PICRUSt in the gut bacterial community of <i>D</i>. <i>rhizophagus</i> across its life cycle.

<p>Warm colors represent high abundances and clear colours represent low abundances.</p

Principal Coordinates Analysis (PCoA) of the bacterial community in the gut of different life stages of <i>D</i>. <i>rhizophagus</i>.

<p>The PCoA was conducted using unweighted (a) and weighted (b) pairwise UniFrac distances among communities of life stages and replicates.</p

Relative abundance of bacterial taxa at phylum, class, family and genus levels in the gut of different life stages of <i>Dendroctonus rhizophagus</i>.

<p>High-quality sequences were sorted into operational taxonomic units (OTUs) according to the open-reference method at a 97% of similarity.</p

Structure and dynamics of the gut bacterial microbiota of the bark beetle, <i>Dendroctonus rhizophagus</i> (Curculionidae: Scolytinae) across their life stages

<div><p>Bark beetles play an important role as agents of natural renovation and regeneration in coniferous forests. Several studies have documented the metabolic capacity of bacteria associated with the gut, body surface, and oral secretions of these insects; however, little is known about how the bacterial community structure changes during the life cycle of the beetles. This study represents the first comprehensive analysis of the bacterial community of the gut of the bark beetle <i>D</i>. <i>rhizophagus</i> during the insect’s life cycle using 454 pyrosequencing. A total of 4 bacterial phyla, 7 classes, 15 families and 23 genera were identified. The <i>α</i>-diversity was low, as demonstrated in previous studies. The dominant bacterial taxa belonged to the Enterobacteriaceae and Pseudomonadaceae families. This low <i>α</i>-diversity can be attributed to the presence of defensive chemical compounds in conifers or due to different morpho-physiological factors in the gut of these insects acting as strong selective factors. Members of the genera <i>Rahnella</i>, <i>Serratia</i>, <i>Pseudomonas</i> and <i>Propionibacterium</i> were found at all life stages, and the first three genera, particularly <i>Rahnella</i>, were predominant suggesting the presence of a core microbiome in the gut. Significant differences in <i>β</i>-diversity were observed, mainly due to bacterial taxa present at low frequencies and only in certain life stages. The predictive functional profiling indicated metabolic pathways related to metabolism of amino acids and carbohydrates, and membrane transport as the most significant in the community. These differences in the community structure might be due to several selective factors, such as gut compartmentalization, physicochemical conditions, and microbial interactions.</p></div

Data_Sheet_1_Metabarcoding of mycetangia from the Dendroctonus frontalis species complex (Curculionidae: Scolytinae) reveals diverse and functionally redundant fungal assemblages.docx

Dendroctonus-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 Dendroctonus 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 Dendroctonus frontalis 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 Entomocorticium, Candida, Ophiostoma-Sporothrix, Ogataea, Nakazawaea, Yamadazyma, Ceratocystiopsis, Grosmannia-Leptographium, Absidia, and Cyberlindnera. Analysis of α-diversity indicated that fungal assemblages of D. vitei showed the highest richness and diversity, whereas those associated with D. brevicomis and D. barberi had the lowest richness and diversity, respectively. Analysis of β-diversity showed clear differentiation in the assemblages associated with D. adjunctus, D. barberi, and D. brevicomis, but not between closely related species, including D. frontalis and D. mesoamericanus and D. mexicanus and D. vitei. A core mycobiome was not statistically identified; however, the genus Ceratocystiopsis was shared among seven beetle species. Interpretation of a tanglegram suggests evolutionary congruence between fungal assemblages and species of the D. frontalis complex. The presence of different amplicon sequence variants (ASVs) of the same genus in assemblages from species of the D. frontalis complex outlines the complexity of molecular networks, with the most complex assemblages identified from D. vitei, D. mesoamericanus, D. adjunctus, and D. frontalis. 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 D. frontalis complex and suggest that minimal apparently specific assemblages are maintained and regulated within mycetangia.</p

Table_1_Metabarcoding of mycetangia from the Dendroctonus frontalis species complex (Curculionidae: Scolytinae) reveals diverse and functionally redundant fungal assemblages.xlsx

Dendroctonus-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 Dendroctonus 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 Dendroctonus frontalis 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 Entomocorticium, Candida, Ophiostoma-Sporothrix, Ogataea, Nakazawaea, Yamadazyma, Ceratocystiopsis, Grosmannia-Leptographium, Absidia, and Cyberlindnera. Analysis of α-diversity indicated that fungal assemblages of D. vitei showed the highest richness and diversity, whereas those associated with D. brevicomis and D. barberi had the lowest richness and diversity, respectively. Analysis of β-diversity showed clear differentiation in the assemblages associated with D. adjunctus, D. barberi, and D. brevicomis, but not between closely related species, including D. frontalis and D. mesoamericanus and D. mexicanus and D. vitei. A core mycobiome was not statistically identified; however, the genus Ceratocystiopsis was shared among seven beetle species. Interpretation of a tanglegram suggests evolutionary congruence between fungal assemblages and species of the D. frontalis complex. The presence of different amplicon sequence variants (ASVs) of the same genus in assemblages from species of the D. frontalis complex outlines the complexity of molecular networks, with the most complex assemblages identified from D. vitei, D. mesoamericanus, D. adjunctus, and D. frontalis. 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 D. frontalis complex and suggest that minimal apparently specific assemblages are maintained and regulated within mycetangia.</p