High overlap in the richness and composition of ectomycorrhizal fungal communities associated with shrubs and co-occurring and trees.

Despite being present in many North American forest understories, the ectomycorrhizal (ECM) fungal communities associated with shrubs have received no prior study. To address this knowledge gap, we characterized the ECM fungal communities on roots of shrubs as well as co-occurring and trees in Minnesota, USA. ECM-colonized root tips from pairs of shrubs and four ECM tree species, , and , growing in close proximity (<1 m), were sampled at the Cedar Creek Ecosystem Science Reserve. ECM fungal communities were assessed using high-throughput sequencing of the ITS2 region. ECM fungal operational taxonomic unit (OTU) richness was equivalent among the two species and their associated shrubs, but significantly higher on -associated shrubs compared with , and -associated shrubs. ECM fungal community composition on shrubs largely mirrored that on each of the and species, although the two communities were significantly different from each other. Further, the same ECM fungal OTUs were commonly encountered on paired -tree host samples, suggesting a high potential for co-colonization by the same fungal individuals. Collectively, these results support the growing consensus that woody understory plants often associate with similar ECM fungal communities as co-occurring tree hosts regardless of phylogenetic relatedness.