Characterizing Ectomycorrhizal Fungal Community Structure and Function of Two Varieties of Pinus clausa That Differ in Disturbance History

Abstract

Despite the immense amount of diversity present in the soil biota, the ecological and evolutionary processes that regulate species diversity and abundance of ectomycorrhizal (ECM) fungi across space and time remain elusive. In forest ecosystems, ECM fungal diversity may be maintained by periodic disturbances which operate at different time scales due to their effects on host genetic and phenotypic characteristics and the associated environment. To investigate the degree to which these factors shape ECM fungal community composition and function, I sampled 10 independent sites for a pine species indicative of an endangered ecosystem, the Florida scrub, where disturbance history has driven the divergence of a single species into two genetically distinct varieties (Pinus clausa var. immuginata and var. clausa). A total of 300 ECM fungal species were identified based on rDNA ITS sequences, but each variety harbors different ECM species composition and function. A follow-up greenhouse experiment, in which the seed from each variety was grown in its own soil (“home”) and in the soil of the other variety (“away”), suggests these communities differentially impact the growth of their host seedlings. While var. clausa seedlings had the same total biomass regardless of soil origin, var. immuginata had higher biomass in their own soil compared to var. clausa. This is likely due to an increased number of ECM colonized tips in the home soil compared to in away soil. Taken together, these results may suggest different evolutionary histories where structure host genetic and phenotypic characteristics may be important for structuring their dynamics with ECM fungi.