Modelling the development of caste-specific gut microbiota in bumblebees

Studies of gut microbiota are highly dependent upon insect models, particularly social insects, due to their simple and consistent gut communities. However, experiments on the important bumblebee pollinator species, Bombus terrestris, focus primarily on the worker caste, neglecting how phenotypic and behavioural differences occurring throughout development, and between castes, may affect the structure of host microbiota. Here we investigated different castes and developmental stages in colonies located in artificial and natural environments, to provide a holistic view of gut microbiota assembly. We found distinct differences in composition between castes and throughout development, and propose the first model of microbial colonisation in developing workers. Microbiota mainly comprised four dominant species that were abundant in both habitats, suggesting that their acquisition is maternally influenced, while environmental exposure affects rare species dynamics. By refining this model species, we highlight how development shapes and forms the gut microbiota in the colony as a whole.