Bee phylosymbiosis: the relative importance of host phylogeny, behavioral traits, and environment

Phylosymbiotic studies investigate how microbiomes recapitulate their host phylogeny and can thus reveal the evolution of host-microbe relationships. In bees, the extent of phylosymbiosis and its relationship with host ecological traits remain unclear. We integrated public bee 16S rRNA metabarcoding data to investigate how host phylogeny and ecological traits affected the bacterial community associated with 178 bee species. Our results highlight only moderate phylosymbiosis patterns in bees, with the corbiculates associating with diverse lineage-specific microbial communities, while the non-corbiculates were predominantly associated with Wolbachia . Across all bee taxa, Wolbachia was also consistently negatively associated with Lactobacillus . Furthermore, our analysis revealed that the host ecological traits had only marginal effects on microbial composition. Although eusocial bees harbored distinct microbiomes, the effect of social behavior was confounded by host phylogeny. Climate showed no general effect across bee taxa, but within some genera, microbiomes were more homogeneous among bees from arid and semi-arid regions than among those from other climatic regions. Together, our findings reveal that broad-scale patterns in bee microbiomes emerge primarily as lineage-specific host–microbe associations, with ecological traits acting only weakly and often at a taxon-specific level.