High overlap in the richness and composition of ectomycorrhizal fungal communities associated with <i>Corylus</i> shrubs and co-occurring <i>Quercus</i> and <i>Pinus</i> trees

Despite being present in many North American forest understories, the ectomycorrhizal (ECM) fungal communities associated with <i>Corylus</i> shrubs have received no prior study. To address this knowledge gap, we characterized the ECM fungal communities on roots of <i>Corylus</i> shrubs as well as co-occurring <i>Quercus</i> and <i>Pinus</i> trees in Minnesota, USA. ECM-colonized root tips from pairs of <i>Corylus</i> shrubs and four ECM tree species, <i>Quercus macrocarpa, Quercus ellipsoidalis, Pinus strobus</i>, and <i>Pinus resinosa</i>, growing in close proximity (&lt;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 <i>Quercus</i> species and their associated <i>Corylus</i> shrubs, but significantly higher on <i>P. strobus</i>–associated <i>Corylus</i> shrubs compared with <i>P. strobus, P. resinosa</i>, and <i>P. resinosa</i>–associated <i>Corylus</i> shrubs. ECM fungal community composition on <i>Corylus</i> shrubs largely mirrored that on each of the <i>Quercus</i> and <i>Pinus</i> species, although the two <i>Pinus</i> communities were significantly different from each other. Further, the same ECM fungal OTUs were commonly encountered on paired <i>Corylus</i>–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.