Microbes have been found in the guts of all animals studied to date. These gut microbiota can provide various services to their host, ranging from breakdown of dietary compounds to pathogen protection. Understanding how host ecology effects the community composition and function of the gut microbiota is a major goal in the field. We employed wild-collected, adult Neotropical butterflies as a study system to ask: (1) How does the gut microbial community vary across host species and dietary guilds? (2) How does the composition of the gut flora compare to that of food microbial communities? (3) Are gut microbes functionally adapted to the chemistry of host foods?
Using Illumina amplicon sequencing (metabarcoding), we characterized bacteria and fungi in the guts of nearly 300 Costa Rican butterflies representing over 50 species and two feeding guilds: fruit-feeders and nectar-feeders. We also characterized the microbes present in fruits and flower nectars at the study site. Finally, we measured the catabolic abilities of the gut microbiota via culture-based assays.
Results/Conclusions
We found that host species identity explained more variation (~25%) in gut community composition than host diet (~4%). However, 85% of a butterfly’s gut bacteria, on average, belonged to species that were also present in the host’s food. Furthermore, the gut microbiota of frugivores exhibited higher levels of amino acid catabolism and lower levels of sugar catabolism than the gut microbiota of nectivores. These differences in catabolic ability mirror the chemical composition of wild fruit juices and nectars. Taken together, our results suggest that host diet filters the gut microbial community by favoring microbes that digest compounds abundant in foods. Whether this filtering occurs pre-ingestion on the food itself, or post-ingestion within the gut, the result is functional matching between gut microbiota and host ecology. Ultimately this could be beneficial to the host if gut microbes aid in digestion, or detrimental if they siphon away nutrients without providing other services.