Understanding the effects of root-associated microbes in explaining plant
community patterns represents a challenge in community ecology. Although
typically overlooked, several lines of evidence point out that nonmycorrhizal,
root endophytic fungi in the Ascomycota may have the potential to drive
changes in plant community ecology given their ubiquitous presence, wide host
ranges, and plant species-specific fitness effects. Thus, we experimentally
manipulated the presence of root endophytic fungal species in microcosms and
measured its effects on plant communities. Specifically, we tested whether (1)
three different root endophyte species can modify plant community structure;
(2) those changes can also modified the way plant respond to different soil
types; and (3) the effects are modified when all the fungi are present. As a
model system, we used plant and fungal species that naturally co-occur in a
temperate grassland. Further, the soil types used in our experiment reflected
a strong gradient in soil texture that has been shown to drive changes in
plant and fungal community structure in the field. Results showed that each
plant species responded differently to infection, resulting in distinct
patterns of plant community structure depending on the identity of the fungus
present. Those effects depended on the soil type. For example, large positive
effects due to presence of the fungi were able to compensate for less
nutrients levels in one soil type. Further, host responses when all three
fungi were present were different from the ones observed in single fungal
inoculations, suggesting that endophyte–endophyte interactions may be
important in structuring plant communities. Overall, these results indicate
that plant responses to changes in the species identity of nonmycorrhizal
fungal community species and their interactions can modify plant community
structure
