Contrasting Bacterial and Fungal Assemblages Across Three Co-Flowering Exotic Plant Species Visited by Stingless Bees in Bali, Indonesia

Flowers are transient, chemically selective habitats in which microbial communities assemble rapidly and can influence nectar chemistry and pollinator behavior, yet the bacterial and fungal assemblages of tropical, bee-foraged plants remain largely uncharacterized and are seldom examined in parallel. We characterized whole-flower bacterial and fungal microbiota of three co-flowering plant species, Antigonon leptopus, Coffea arabica and Xanthostemon chrysanthus, growing at a single site in Bali, Indonesia, and visited by the stingless bee Tetragonula laeviceps, using paired 16S rRNA and ITS2 amplicon profiling. The three composite samples differed markedly in composition, with fewer than four percent of taxa shared among all three plants despite close spatial proximity and shared climate. Bacterial communities were dominated by Proteobacteria and fungal communities were dominated by Ascomycota and included lineages characteristic of nectar and of bee-associated environments, notably Asaia and other Acetobacteraceae, Pantoea and Rosenbergiella. The two markers did not order the hosts congruently in the samples analyzed: bacterial communities grouped A. leptopus with C. arabica, whereas fungal communities grouped it with X. chrysanthus, a decoupling consistent across clustering, taxon sharing and diversity ranking. These findings indicate that these floral communities differed markedly despite close spatial proximity and shared climate and suggest possible cross-kingdom differences in community organization that warrant examination in replicated designs.