Ectomycorrhizal fungal endemism and rainforest nutrition in Pacific Northeast
Date
2023-05-01
Authors
McPolin, Marie Claire
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Abstract
Considerable research exists on how niche processes and spatial trade-offs structure the species richness observed in ectomycorrhizal fungal (EMF) communities, but little attention has been paid to how this might relate to the high levels of endemism reported in these communities.
As endemism is typically associated with habitat specialization, I anticipated that EMF species endemic to the distinct high available nitrogen (N), low available phosphorous (P) soils of the Pacific Northeastern (PNE) temperate rainforests would display greater macronutrient concentration, indicative of superior nutrient exploitation. I measured both the sporocarp nutrition and the root tip abundance of EMF species on a mature forest (CWHVm biogeoclimatic zone) of Sitka spruce and western hemlock and determined fungal endemism using UNITE database. Endemic species, representing close to 50% of species found on root tips, had significantly higher sporocarp N, K and Mg concentrations than cosmopolitan species, but comparable P levels. Sporocarp N and P were strongly correlated, and species with higher N levels showed an increasing N:P ratio, supporting existing evidence for the N cost of organic P-acquiring enzymes. Endemics were more likely to occur on western hemlock (a coastally restricted genus) plots than Sitka spruce (a circumpolar genus) plots and became more frequent on root tips as inorganic P levels in the soil decreased. Endemics represented a diverse group, with moderate but non-random dispersion across the phylogeny; The Inocybaceae family were predominantly endemic, while Cortinariaceae was largely cosmopolitan, highlighting some role of phylogenetic niche conservatism in certain lineages, but not as an overall pattern. I conclude that endemic EMF account for a significant portion of fungi most well adapted to PNE coastal soils, have preference for coastally restricted Tsuga, and are expected to provide superior N nutrition to their tree hosts.
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Keywords
soil ecology, ectomycorrhizal fungi, fungal endemism, local adaptation