Abstract:
Ferns are known to have a lower incidence of mycorrhization than angiosperms. It
has been suggested that this results from carbon being more limiting to fern growth
than nutrient availability, but this assertion has not been tested yet. In the present
study, we took advantage of a fertilization experiment with nitrogen and phosphorus
on cloud forest plots of the Ecuadorean Andes for 15 years. A previous analysis
revealed changes in the abundances of fern species in the fertilized plots compared
to the control plots and hypothesized that this might be related to the responses of
the mycorrhizal relationships to nutrient availability. We revisited the plots to assess
the root-associated
fungal communities of two epiphytic and two terrestrial fern
species that showed shifts in abundance. We sampled and analyzed the roots of 125
individuals following a metabarcoding approach. We recovered 1382 fungal ASVs, with
a dominance of members of Tremellales (Basidiomycota) and Heliotales (Ascomycota).
The fungal diversity was highly partitioned with little overlap between individuals. We
found marked differences between terrestrial and epiphytic species, with the latter
fundamentally missing arbuscular mycorrhizal fungi (AMF). We found no effect of
fertilization on the diversity or relative abundance of the fungal assemblages. Still, we
observed a direct impact of phosphorus fertilization on its concentration in the fern
leaves. We conclude that fern–fungi relationships in the study site are not restricted
by nutrient availability and suggest the existence of little specificity on the fungal
partners relative to the host fern species.
