Melipona stingless bees and honey microbiota reveal the diversity, composition, and modes of symbionts transmission.

The Melipona gut microbes differ from other social bees, with the absence of crucial corbiculate core gut symbionts and the high occurrence of environmental strains. We studied the microbial diversity and composition of three Melipona species and their honey to understand which strains are obtained by horizontal transmission (HT) from the pollination environment; or represent symbionts co-evolved with Melipona by HT from the hive/food stores or vertical transmission (VT) via social interactions. Bees harbored higher microbial alpha diversity and a different and more species-specific bacterial composition than honey. Otherwise, the fungal communities of bee and honey samples are less dissimilar. As expected, the core symbionts Snodgrassella and Gilliamella were absent in bees that had a prevalence of Lactobacillus Firm-5, environmental Lactobacillaceae, Bifidobacteriaceae and Acetobacteraceae. Also, Pectinatus and Floricoccus have habitat preferences for bees, putatively representing novel symbionts from the environment that co-evolved via VT among generations. Fructilactobacillus found in bees possibly had HT to bees from honey stores. Metschnikowia yeasts, consistent in all bees and honey samples, might have HT to bees from food stores. Similarly, Saccharomycetales might have HT from honey or plants/flowers to bees. This work contributes to the understanding of Melipona symbionts and their modes of transmission.