Gut microbiota variation of a tropical oil-collecting bee species far exceeds that of the honeybee.

Introduction: Interest for bee microbiota has recently been rising, alleviating the gap in knowledge in regard to drivers of solitary bee gut microbiota. However, no study has addressed the microbial acquisition routes of tropical solitary bees. For both social and solitary bees, the gut microbiota has several essential roles such as food processing and immune responses. While social bees such as honeybees maintain a constant gut microbiota by direct transmission from individuals of the same hive, solitary bees do not have direct contact between generations. They thus acquire their gut microbiota from the environment and/or the provision of their brood cell. To establish the role of life history in structuring the gut microbiota of solitary bees, we characterized the gut microbiota of from a beach population in Mayagüez, Puerto Rico. Females provide the initial brood cell provision for the larvae, while males patrol the nest without any contact with it. We hypothesized that this behavior influences their gut microbiota, and that the origin of larval microbiota is from brood cell provisions.

Methods: We collected samples from adult females and males of ( = 10 each,  = 20), larvae ( = 4), and brood cell provisions ( = 10). For comparison purposes, we also sampled co-occurring female foragers of social ( = 6). The samples were dissected, their DNA extracted, and gut microbiota sequenced using 16S rRNA genes. Pollen loads of and were analyzed and interactions between bee species and their plant resources were visualized using a pollination network.

Results: While we found the gut of contained the same phylotypes previously reported in the literature, we noted that the variability in the gut microbiota of solitary was significantly higher than that of social . Furthermore, the microbiota of adult mostly consisted of acetic acid bacteria whereas that of mostly had lactic acid bacteria. Among , we found significant differences in alpha and beta diversity between adults and their brood cell provisions (Shannon and Chao1  < 0.05), due to the higher abundance of families such as Rhizobiaceae and Chitinophagaceae in the brood cells, and of Acetobacteraceae in adults. In addition, the pollination network analysis indicated that had a stronger interaction with sp. and a weaker interaction with while interactions between and its plant resources were constant with the null model.

Conclusion: Our data are consistent with the hypothesis that behavioral differences in brood provisioning between solitary and social bees is a factor leading to relatively high variation in the microbiota of the solitary bee.