Flowering Plant Microbiomes and Network Interactions Across an Urban Gradient

We used flowers to explore how ephemeral anthosphere microbiomes differ among flowering plant species and along an urban gradient. Here, we sequenced 16S rRNA for bacteria, ITS1 for fungi and rbcL for plant DNA from 10 different plant species sampled to characterise anthosphere microbiomes along an urban gradient and identify important network interactions. Bacterial and fungal flower microbiomes significantly differed in diversity across plant species, especially among Asteraceae and Fabaceae. Across all analyses, four taxa, the bacteria Pantoea and Rosenbergiella and the fungi Alternaria and Cladosporium were highly prevalent and contributed to the majority of microbiome composition differences observed between plant species. These four taxa harbour strains or species that may be either pathogenic or beneficial to plants. Across a land use gradient, the plant community bacterial and fungal microbiome was stable and consistent. Flower-plant networks confirmed all focal flower families in abundance on each sampled flower, with the addition of Paulowniaceae, suggesting that pollinators visiting the focal flowers also visit this plant family. Our findings reveal that anthosphere microbiomes are diverse at the plant community level and encouragingly remain robust against urbanisation.