DOI: 10.5061/dryad.9zw3r22jx
title: Endemic species of ectomycorrhizal fungi support the exceptional productivity of a temperate rainforest

description: Endemic species of ectomycorrhizal fungi (EMF) can be found throughout
 many forest biomes, but it is unclear whether their localized distribution
 is dictated by deterministic processes or geographical barriers to
 dispersal. We investigated the adaptive characteristics and prevalence of
 endemic versus cosmopolitan EMF species in perhumid temperate rainforests
 of southwestern Vancouver Island (Canada), characterized by moist, acidic
 soils with high nitrogen (N) supply alongside low phosphorus (P) and
 cation availability. Endemic EMF species, representing almost half of the
 community, had significantly higher sporocarp N (24% increase), potassium
 (+16%), and magnesium (+17%) concentrations than cosmopolitan species.
 Sporocarp P concentrations were low overall, reflecting limited soil P
 availability, and did not differ by fungal range. However, sporocarp N%
 and P% were well correlated, and species with higher N concentrations
 showed an increasing N:P ratio, supporting evidence for the N allocation
 required to produce organic P-acquiring enzymes. Endemics were also more
 likely to occur on Tsuga heterophylla (a disjunct host genus) than Picea
 sitchensis (a circumpolar genus), but pairwise comparisons indicated no
 differences in abundance by fungal range for either host. Endemics
 represented a diverse group, with moderate dispersion across the
 phylogeny. The Inocybaceae and Thelephoraceae families had high
 proportions of endemic taxa, while Cortinariaceae was largely
 cosmopolitan, highlighting some niche conservatism in certain lineages but
 not as an overall pattern. We conclude that superior adaptive traits in
 relation to perhumid soils were skewed towards the endemic community,
 underscoring the important contribution of these localized fungi to
 rainforest nutrition and productivity. 
description: In the fall of
 2020, over a six-week period (October 5-November 15) we visited each plot
 three times to search for fleshy, terricolous sporocarps. We selected
 sporocarps that were fresh and free from insect damage and strove to
 obtain composite samples for each fungal species, typically 3–6 individual
 sporocarps, from over the entire plot area. Following collection,
 sporocarps were cleaned of debris and dried in a 60°C convection oven for
 24 h (larger sporocarps were sliced in half to facilitate drying). Species
 identity was confirmed by molecular DNA of the fungal ITS region using a
 small piece of dried sporocarp, and the remainder of the sample (cap and
 stipe) was ground to &lt; 2 mm for nutritional analysis.
 In June 2021, soil cores approximately 12 cm in diameter and 15
 cm in depth were removed with a soil knife at 15 random locations in each
 of the ten plots. The soil core included upper mineral soil and organic
 horizons. Samples were returned to the laboratory and kept at 4°C during
 processing. Each core was submerged under water in a large pan and random
 portions of roots removed for examination under a dissecting microscope.
 Fresh, vigorous colonies of EMF root tips were detached using tweezers.
 Composited root tips from three soil cores were combined into one vial,
 for a total of 5 subsamples per plot (n = 50 for the study). This process
 was conducted by two personnel for 30 minutes per soil core, and resulted
 in 7–10 mL of fresh root tips per vial. The samples were then freeze-dried
 and ground with a ball mill before DNA extraction.