Diversity and community structure of ericoid mycorrhizal fungi in European bogs and heathlands across a gradient of nitrogen deposition.

Despite the ecological significance of ericoid mycorrhizal fungi, little is known about the abiotic and biotic factors driving their diversity and community composition. To determine the relative importance of abiotic and biotic filtering in structuring ericoid mycorrhizal fungal communities, we established 156 sampling plots in two highly contrasting environments but dominated by the same Ericaceae plant species: waterlogged bogs and dry heathlands. Plots were located across 25 bogs and 27 dry heathlands in seven European countries covering a gradient in nitrogen deposition and phosphorus availability. Putatively ericoid mycorrhizal fungal communities in the roots of 10 different Ericaceae species were characterized using high-throughput amplicon sequencing. Variation in ericoid mycorrhizal fungal communities was attributed to both habitat and soil variables on the one hand and host plant identity on the other. Communities differed significantly between bogs and heathlands and, in a given habitat, communities differed significantly among host plant species. Fungal richness was negatively related to nitrogen deposition in bogs and phosphorus availability in bogs and heathlands. Our results demonstrate that both abiotic and biotic filtering shapes ericoid mycorrhizal fungal communities and advocate an environmental policy minimizing excess nutrient input in these nutrient-poor ecosystems to avoid loss of ericoid mycorrhizal fungal taxa.