Exotic plant invasions are a major driver of global environmental change that can significantly alter ecosystem function and reduce native plant communities. Soil microbes can play an important role in plant establishment, growth, and plant competitive interactions, however relatively little is known about the community composition of soil microbes between native and non-native tree species. Norway maple, an invasive species found in North American temperate forests, can decrease plant diversity by outcompeting native species such as sugar maple. We collected root systems of co-occurring maple seedlings over one growing season and addressed the following questions: 1) Do communities of root associated microbes vary between native sugar maple and invasive Norway maple and 2) do root colonization levels of arbuscular mycorrhizal fungi (AMF) and dark septate endophytic fungi differ between the two species? We used the magnified grid-intersect method to determine fungal root colonization levels and Illumina MiSeq sequencing to characterize the microbial communities associated with the roots of the two host species.
Results/Conclusions
We found significant differences in the community structure of bacteria and fungi, while no differences were detected in the AMF communities. Although sugar and Norway maple shared many microbial operational taxonomic units (OTUs), they differed in the abundance of specific bacterial and fungal OTUs. In particular, sugar maple harbors higher abundances of certain potentially pathogenic bacterial and fungal OTUs. These results suggest that reduced root pathogens could possibly lead to “enemy release” in the introduced species thereby promoting invasion. We did not find support for facilitation via enhanced mutualistic interactions compared to the sugar maple, but we did observe high AMF colonization rates in introduced Norway maple, which demonstrates its compatibility with native AMF. Perhaps more interestingly, we found evidence that certain potentially pathogenic microbes are less abundant on the introduced species, supporting the enemy release hypothesis. In sum, we show that co-occurring native and invasive maple species host distinct root-associated microbial communities, highlighting the need to consider microbial diversity when assessing the role of plant soil interactions in the context of plant invasions.