Microbial communities of lycaenid butterflies do not correlate with host diet

Herbivorous lifestyles present numerous challenges, yet many animals – especially insects – are successful herbivores. There are a variety of herbivore counteradaptations to plant defenses, and growing body of research describes the role of symbiotic gut bacteria in mediating herbivorous diets among insects. However, persistent bacterial symbioses have not been described in detail for Lepidoptera, despite being one of the largest herbivore groups on earth. We surveyed larvae from 31 species of lycaenid butterflies and compared the gut bacterial communities associated with species with diverse diets. Contrary to our expectations, we find that the bacterial communities of carnivorous and herbivorous caterpillars do not differ in richness, diversity, or composition. Many of the observed bacterial genera are commonly found in soil and plant surfaces, and we detected known homopteran endosymbionts in the guts of homopterophagous species, suggesting that larvae acquire many of the gut bacteria from their food and environment. These results indicate that lycaenid butterflies do not rely on bacterial symbioses to mediate their diverse diets, and provide further evidence of depauperate bacterial communities among Lepidoptera.