The Invisible Web: Linking Diet and Gut Microbiota Across Time and Space in Odonates

Abstract The complex relationship between insects and their gut microbiota has become a central theme in host–microbe ecology, revealing profound effects on host fitness and interactions. Yet, how gut microbial communities—and their primary determinant, diet—vary across space and time in natural insect populations remains largely unexplored. Understanding these dynamics is essential for linking microbial variation with host biology. We investigated bacterial gut microbiota and dietary patterns in two odonate species, Sympetrum vulgatum and Lestes sponsa , across their flight season and three locations in southern Finland. Using faecal DNA metabarcoding of the cytochrome c oxidase subunit I (COI) gene for diet and 16 S rRNA gene for gut microbiota, we examined spatiotemporal changes and their associations. Season, location, and host species affected both dietary and bacterial diversity. The observed parallel responses of dietary composition and microbial communities highlight that the same ecological factors shaping insect feeding behaviour also influence their associated microbiota, illustrating the dynamic and context-dependent nature of insect–microbe interactions in the wild and emphasizing the need for broader ecological perspectives in microbiome research.