Linked networks reveal dual roles of insect dispersal and species sorting for bacterial communities in flowers

Due to the difficulty of tracking microbial dispersal, it rarely possible to disentangle the relative importance of dispersal and species sorting for microbial community assembly. Here, we leverage a detailed multilevel network to examine drivers of bacterial community assembly within flowers. We show that plant species with similar visitor communities tend to have similar bacterial communities, and visitor identity to be more important than dispersal rate in structuring floral bacterial communities. However, plants occupied divergent positions in plant-insect and plant-microbe networks, suggesting an important role for species sorting. Taken together, our analyses suggest dispersal is important in determining similarity in microbial communities across plant species, but not as important in determining structural features of the floral bacterial network. A multilevel network approach thus allows us to address features of community assembly that cannot be considered when viewing networks as separate entities.