Two gut community enterotypes recur in diverse bumblebee species

Pollinating insects are key to the evolutionary and ecological success of fl owering plants and enable much of the diversity in the human diet. Gut microbial communities likely impact pollinators in diverse ways, from nutrition to defense against disease [1,2]. Honeybees and bumblebees harbor a simple yet specialized gut microbiota [3] dominated by several newly described bacterial species, including Gilliamella apicola, Frischella perrara, Snodgrassella alvi and specialized species of Lactobacillus. These bacterial groups are absent from the guts of other bees studied to date [3,4]. Although simple, the gut microbiota of honeybees and bumblebees share several similarities to those of mammals. First, both are socially transmitted, and young individuals are colonized through interactions with older individuals [5]. Second, in guts of both humans and honeybees, a particular bacterial species is typically represented by many strains; for example, in honeybees, both G. apicola and S. alvi occur as numerous strains with distinct gene sets [6]. Third, in both humans and social bees, individual hosts vary in the composition of their gut communities [5,7,8]. This variation likely refl ects the interplay of symbiont specialization to distinct hosts and opportunity for transfer among hosts. A striking fi nding for human gut communities has been the occurrence of enterotypes, which are defi ned as “densely populated areas in a multidimensional space of community composition” [8]. Three enterotypes are found in diverse human populations, a result mirrored in chimpanzees [9]. In both humans and chimpanzees one enterotype shows overrepresentation Correspondence