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The impact of urbanization on the spatial dynamic of the phyllosphere microbial community of common milkweed
Mobina Gholamhosseini, Anne Bruneau, Geneviève Lajoie
Urbanization is a key aspect of global change and is characterized by drastic changes in the abiotic (e.g., extreme air temperature and pollution) and biotic context of species interactions, namely plant-microbe interactions. Despite the critical role of the phyllosphere (i.e., leaf) microbiome in enhancing plant growth and health, its response to urbanization remains poorly understood. Urbanization may shift the balance between key mechanisms of microbial community assembly, such as selection and dispersal, thereby impacting leaf symbioses. This study aims to investigate how potential changes in selection through abiotic stressors and host plant traits, alongside the role of dispersal across host plants can affect the composition and diversity of epiphytic microbial communities of common milkweed (Asclepias syriaca L.) across a gradient of increasing urbanization intensity. Using amplicon sequencing, we compared the foliar microbiota of this species across urban-to-nonurban gradients in three Canadian regions (Montreal, Toronto, and Quebec) during the flowering stage. Our preliminary results indicate that gradient, region, and their interactions significantly influence alpha diversity and beta diversity of epiphytic bacteria communities. Alpha diversity increases with anthropogenic pressures, with urban communities in Montreal harbouring the most diverse bacterial taxa, followed by Toronto and Quebec. Conversely, bacterial relative abundance declines with urbanization, with nonurban sites in Montreal having the highest abundance of bacterial taxa. These findings emphasize the impacts of urbanization on the foliar bacterial community assembly and underscore the need to integrate microbiome studies into urban ecological frameworks to better understand and manage urban biodiversity.
Keywords: Common milkweed, diversity, epiphytic bacteria, phyllosphere, urbanization
