The evolutionary and environmental factors that shape fungal biogeography are incompletely understood. Here, we assemble a large dataset consisting of previously generated mycobiome data linked to specific geographical locations across the world. We use this dataset to describe the distribution of fungal taxa and to look for correlations with different environmental factors such as climate, soil and vegetation variables. Our meta-study identifies climate as an important driver of different aspects of fungal biogeography, including the global distribution of common fungi as well as the composition and diversity of fungal communities. In our analysis, fungal diversity is concentrated at high latitudes, in contrast with the opposite pattern previously shown for plants and other organisms. Mycorrhizal fungi appear to have narrower climatic tolerances than pathogenic fungi. We speculate that climate change could affect ecosystem functioning because of the narrow climatic tolerances of key fungal taxa.

High-throughput DNA sequencing has dramatically transformed several areas of biodiversity research including mycology. Despite limitations, high-throughput sequencing is nowadays a predominant method to characterize the alpha and beta diversity of fungal communities. Across the papers utilizing high-throughput sequencing approaches to study natural habitats in terrestrial ecosystems worldwide, > 200 studies published until 2019 have generated over 250 million sequences of the primary mycological metabarcoding marker, the nuclear ribosomal internal transcribed spacer 2 (ITS2). Here we show that at a 97% sequence similarity threshold, the total richness of non-singleton fungal taxa across the studies published so far is 1.08 million, mostly Ascomycota (56.8% of the taxa) and Basidiomycota (36.7% of the taxa). The Chao-1 estimate of the total extant fungal diversity based on this dataset is 6.28 million taxa, representing a conservative estimate of global fungal species richness. Soil and litter represent the habitats with the highest alpha diversity of fungi followed by air, plant shoots, plant roots and deadwood with Chao-1 predictions, for samples containing 5000 sequences, of 1219, 569, 392, 228, 215 and 140 molecular species, respectively. Based on the high-throughput sequencing data, the highest proportion of unknown fungal species is associated with samples of lichen and plant tissues. When considering the use of high-throughput sequencing for the estimation of global fungal diversity, the limitations of the method have to be taken into account, some of which are sequencing platform-specific while others are inherent to the metabarcoding approaches of species representation. In this respect, high-throughput sequencing data can complement fungal diversity predictions based on methods of traditional mycology and increase our understanding of fungal biodiversity.

Summary: Arbuscular mycorrhizal (AM) fungi are crucial mutualistic symbionts of the majority of plant species, with essential roles in plant nutrient uptake and stress mitigation. The importance of AM fungi in ecosystems contrasts with our limited understanding of the patterns of AM fungal biogeography and the environmental factors that drive those patterns. This article presents a release of a newly developed global AM fungal dataset (GlobalAMFungi database, https://globalamfungi.com) that aims to reduce this knowledge gap. It contains almost 50 million observations of Glomeromycotinian AM fungal amplicon DNA sequences across almost 8500 samples with geographical locations and additional metadata obtained from 100 original studies. The GlobalAMFungi database is built on sequencing data originating from AM fungal taxon barcoding regions in: i) the small subunit rRNA (SSU) gene; ii) the internal transcribed spacer 2 (ITS2) region; and iii) the large subunit rRNA (LSU) gene. The GlobalAMFungi database is an open source and open access initiative that compiles the most comprehensive atlas of AM fungal distribution. It is designed as a permanent effort that will be continuously updated by its creators and through the collaboration of the scientific community. This study also documented applicability of the dataset to better understand ecology of AM fungal taxa.

Summary: Gradients in species diversity across elevations and latitudes have fascinated biologists for decades. While these gradients have been well documented for macroorganisms, there is limited consensus about their universality, shape and drivers for microorganisms, such as fungi, despite the importance of fungal diversity for ecosystem functions and services. We conducted a comprehensive survey of fungal species richness in forests across 17 elevational transects along a latitudinal gradient covering the continental scale of Europe. Diversity patterns along elevational and latitudinal gradients differed among fungal ecological guilds. Diversity of saprotrophs declined with elevation while ectomycorrhizal (ECM) fungal diversity peaked in mid‐elevations. Moreover, the diversity of root endophytic fungi increased with latitude but did not change with elevation. Bayesian species distribution modeling suggests that fungal diversity is structured by deterministic rather than stochastic drivers. Importantly, ECM fungal diversity pattern persists even after accounting for the effects of environmental conditions. These results suggest that environmental conditions differentially shape the diversity of fungal guilds along elevational and latitudinal gradients, but this goes beyond soil and climatic factors in the case of ECM fungi. This study paves the way toward a better understanding of fungal diversity gradients across elevations and latitudes, with possible implications for macroecological theory, conservation and management.

Deadwood represents an important carbon stock and contributes to climate change mitigation. Wood decomposition is mainly driven by fungal communities. Their composition is known to change during decomposition, but it is unclear how environmental factors such as wood chemistry affect these successional patterns through their effects on dominant fungal taxa. We analysed the deadwood of Fagus sylvatica and Abies alba across a deadwood succession series of >40 years in a natural fir-beech forest in the Czech Republic to describe the successional changes in fungal communities, fungal abundance and enzymatic activities and to link these changes to environmental variables. The fungal communities showed high levels of spatial variability and beta diversity. In young deadwood, fungal communities showed higher similarity among tree species, and fungi were generally less abundant, less diverse and less active than in older deadwood. pH and the carbon to nitrogen ratio (C/N) were the best predictors of the fungal community composition, and they affected the abundance of half of the dominant fungal taxa. The relative abundance of most of the dominant taxa tended to increase with increasing pH or C/N, possibly indicating that acidification and atmospheric N deposition may shift the community composition towards species that are currently less dominant.