Intraspecific trait variation contributes to functional diversity patterns at the sapling level in ectomycorrhizal communities

Background/Question/Methods

One of the most pressing challenges of fungal trait-based ecology is to find efficient ways to measure ecologically relevant traits at the individual scale. This is particularly challenging for soil-borne and root-borne fungi, such as ectomycorrhizal fungi. To circumvent that problem, collecting ectomycorrhizal root tips can be a useful way to sample individuals in ectomycorrhizal communities. These tips can be analyzed with high-throughput for their surface enzymatic activities in parallel using plate-based assays. Here, we characterized the surface enzymatic activities of >800 ectomycorrhizal root tips collected from fir saplings in a mixed forest in Québec. We evaluated (1) the intraspecific trait variation and (2) the contribution of such trait variation to community-level patterns of trait range and dispersion.

Results/Conclusions

We found that most of the constrained variation in enzymatic activity was explained by fungal taxonomic identity. Intraspecific variation, however, decreased functional richness and dispersion, suggesting a functional convergence at the sapling scale. Although we may hypothesize that ectomycorrhizal fungi adjust enzyme secretion to local environmental conditions, we detected only weak correlation patterns between enzymatic activities and soil physico-chemistry, suggesting that appropriate proxies for environmental filters remain to be unraveled. Overall, our results suggest that intraspecific variation in ectomycorrhizal communities can leave an imprint on patterns of functional diversity, but the importance of fungal identity as a driver of enzymatic activity support a role for DNA-based characterization of fungal communities as a way to convey information about (1) community assembly and (2) ecosystem-level consequences of shifts in fungal community structure.