Ambrosia gall midges are endophagous insect herbivores whose larvae live enclosed within a single gall for their entire development period. They may exhibit phytomycetophagy, a remarkable feeding mode that involves the consumption of plant biomass and mycelia of their cultivated gall symbionts. Thus, AGMs are ideal model organisms for studying the role of microorganisms in the evolution of host specificity in insects. However, compared to other fungus-farming insects, insect-fungus mutualism in AGMs has been neglected. Our study is the first to use DNA metabarcoding to characterize the complete mycobiome of the entire system of the gall-forming insects as we profiled gall surfaces, nutritive mycelia, and larvae. Interestingly, larval mycobiomes were significantly different from their nutritive mycelia, although Botryosphaeria dothidea dominated the nutritive mycelia, regardless of the evolutionary separation of the tribes studied. Therefore, we confirmed a long-time hypothesized paradigm for the important evolutionary association of this fungus with AGMs.

• Keywords
• Asphondylia, Cecidomyiidae, Lasioptera, ambrosia gall midge, fungiculture, larval mycobiome, metabarcoding, nutritive mycelium, phytomycetophagy,
• MeSH
• Ambrosia MeSH
• Diptera * MeSH
• Insecta MeSH
• Larva MeSH
• Mycobiome * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH

Despite an increasing number of studies on caterpillar (Insecta: Lepidoptera) gut microbiota, bacteria have been emphasized more than fungi. Therefore, we lack data on whether fungal microbiota is resident or transient and shaped by factors similar to those of bacteria. We sampled nine polyphagous caterpillar species from several tree species at multiple sites to determine the factors shaping leaf and gut bacterial and fungal microbiota as well as the extent to which caterpillars acquire microbiota from their diet. We performed 16S and ITS2 DNA metabarcoding of the leaves and guts to determine the composition and richness of the respective microbiota. While spatial variables shaped the bacterial and fungal microbiota of the leaves, they only affected fungi in the guts, whereas the bacteria were shaped primarily by caterpillar species, with some species harboring more specific bacterial consortia. Leaf and gut microbiota significantly differed; in bacteria, this difference was more pronounced. The quantitative similarity between leaves and guts significantly differed among caterpillar species in bacteria but not fungi, suggesting that some species have more transient bacterial microbiota. Our results suggest the complexity of the factors shaping the gut microbiota, while highlighting interspecific differences in microbiota residency within the same insect functional group.

• MeSH
• Bacteria genetics   MeSH
• Fungi genetics   MeSH
• Lepidoptera * microbiology   MeSH
• Mycobiome * MeSH
• Gastrointestinal Microbiome * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH