Cycad-feeding insects share a core gut microbiome

Five insect species including three species of weevils (Coleoptera) and two species of lycaenid butterflies (Lepidoptera) that feed exclusively on the carcinogenic and neurotoxic tissues of cycads were found to share a core set of bacterial phylotypes, including the bacterium Raoultella ornithinolytica, which has known anti-cancer and nitrogen-fixing capabilities. The other shared bacteria belong to lineages that include insect-associated and extremophilic taxa. The presence of Raoultella ornithinolytica and an unknown Enterobacteriaceae was in contrast to a set of non-cycadfeeding relatives of these insects, none of which contained this same set of shared bacterial phylotypes. Given the considerable phylogenetic distance between the cycadivorous insect species as well as the fact that shared microbiota are not found in their non-cycad-feeding relatives, our data suggest that this core set of shared bacteria are important in helping cycad feeders detoxify their poisonous host plants.