Global patterns and determinants of bacterial communities associated with ectomycorrhizal root tips of Alnus species

Abstract

<p>Plant-soil interactions affect plant health, productivity and vegetation structure. Although recent advances in sequencing and computational tools have facilitated research on these complex interactions, we still have a poor understanding of the relative influence of biotic and abiotic factors on their community assembly. Here we aimed to determine the relative contributions of <i>Alnus</i> species and their associated mycorrhizal fungi, spatial, edaphic and climatic factors to the structure of root-associated bacterial communities. We used high-throughput identification of bacteria based on 369 ectomycorrhizal root tips of 19 <i>Alnus</i> species from 85 sites across the globe. We found that the <i>Alnus</i> species phylogeny was the primary determinant for the composition of root-associated bacterial communities, followed by edaphic, spatial and climate variables. Moreover, we observed <i>Alnus</i> species-specificity for some highly abundant bacterial phylotypes. These results reflect the importance of biotic variables in shaping root-associated bacterial communities and suggest that different processes underlie root-associated and soil bacterial communities on a global scale.</p>