Local Scale Biogeographic Variation in the Magnolia (Magnolia grandiflora) Phyllosphere

The phyllosphere (aerial plant surfaces colonized by microorganisms) remains an understudied ecosystem in terms of bacterial biogeography, particularly at intermediate or local spatial scales. This study characterized the phyllosphere bacterial community on the leaves of 87 <i>Magnolia grandiflora</i> trees sampled throughout a small town, encompassing an area of approximately 60 km². Sequencing of the 16S ribosomal RNA gene revealed the dominant bacterial phyla to be Alphaproteobacteria, Bacteroidetes, and Acidobacteria, consistent with other studies of the phyllosphere. There was a small but significant relationship between the phyllosphere community similarity and the distance between the trees (i.e., trees further apart were more likely to have dissimilar bacterial communities). There was also a relationship between the assigned categories of tree height (low, medium, high) and the phyllosphere bacterial community composition, with the trees in the high category having more diverse bacterial communities on their leaves than the shorter trees. This study provides insight into the relationship between phyllosphere community composition and host tree characteristics and shows that the distance between <i>M. grandiflora</i> trees has a significant, albeit low, influence on bacterial composition. These findings contribute to a deeper understanding of phyllosphere microbiome biogeography, highlighting how individual tree characteristics and spatial proximity shape phyllosphere bacterial communities.