Host identity determines gut bacterial community structure in Neotropical butterflies

Background/Question/Methods

Host taxonomy at high-level ranks has been shown to be a determining factor in the gut community composition of animals, but it is unclear whether this relationship is present at lower taxonomic levels. A significant correlation at the genus and species level would indicate that the gut community is closely linked to host evolution. To elucidate the relationship between host identity and gut community structure, we compared the gut flora of several species of Neotropical butterflies.  These species were selected within the same feeding guild to control for the effects of host diet. We hypothesized that host species would be a significant determinant of gut community composition, and furthermore, that turnover between the gut flora of different species would reflect the hosts’ evolutionary distance. Lepidoptera is a diverse order both taxonomically and ecologically, making it a suitable system to investigate central questions regarding the determinants and functions of the gut community. We collected 135 adult male individuals spanning 14 species, 10 genera, and 3 subfamilies of fruit-feeding butterflies at La Selva Biological Station in Costa Rica. To compare microbial communities, we dissected the guts and used Illumina high throughput sequencing on amplified 16s rRNA. 

Results/Conclusions

Analysis of Illumina sequences revealed 964 cumulative OTUs that were dominated by the four major bacterial phyla typically found in animal guts: Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria.  An ordination of pairwise community distances indicated that butterfly gut communities cluster by host taxonomy.  These results were supported by a nested permutational MANOVA test which revealed that all host taxonomic levels explained a significant proportion of variance in gut communities, but that more granular taxonomic groups explained variance unaccounted for by higher groups (Subfamily: p<0.001, R² =0.04, Tribe: p<0.001, R²=0.09, Genus: p<0.001, R²=0.17 Species: p<0.003, R²=0.21). Differences in gut communities were characterized by both relative abundance of OTUs and overall species richness. These results indicate that butterflies gut communities are structured in host specific ways and prompt further inquiry into the role that the gut flora plays in butterfly ecology and evolution.