Abstract

Plant-microbe associations are ubiquitous, but parsing the contributions of dispersal, host filtering, competition, and the environment on microbial community composition is challenging. Floral nectar-inhabiting microbes offer a tractable system to disentangle community assembly processes. We inoculated a synthetic community of yeasts and bacteria into nectars of 31 phylogenetically diverse plant species while excluding pollinators. We monitored weather conditions and, after 24 hours, collected and cultured communities. We found a strong signature of plant species on resulting microbial abundance and community composition, in part explained by plant phylogeny and nectar peroxide content, but not measured floral morphological traits. Higher maximum and minimum temperatures increased microbial growth overall and favored certain microbes over others. Our work supports the roles of plant identity and abiotic conditions in assembly and growth of plant-associated microbial communities and finds evidence for diversity-productivity relationships within plant-associated microbiomes.