Biogeography and community assembly of soil fungi from alpine meadows in southwestern China show the importance of climatic selection

Soil fungi are pivotal in alpine and arctic ecosystems that are vulnerable to climate changes. Previous studies have shown broad connections between soil fungi in the arctic and alpine regions, but most of these studies are mainly from Europe and North America, with more sporadic studies from East Asia. Currently, little is known about the biogeographic relationships between soil fungi in alpine meadows of southwestern China (AMSC) and other regions of the world. In addition, the regional-scale spatial patterns of fungal communities in the AMSC, as well as their driving factors and ecological processes, are also poorly understood. In this study, we collected roots and surrounding soils of two dominant ectomycorrhizal plants, Bistorta vivipara and B. macrophylla from the AMSC, and performed bioinformatic and statistical analyses based on high-throughput sequencing of ITS2 amplicons. We found that: (1) fungi from the AMSC were closely related with those from boreal forests and tundra, and saprotrophic fungi had higher dispersal potential than ectomycorrhizal fungi; (2) community compositions exhibited clear divergences among geographic regions and between root and soil samples; (3) climate was the predominant factor driving regional-scale spatial patterns but had less explanatory power for saprotrophic and total fungi from roots than those from soils; (4) homogeneous selection and drift were the key ecological processes governing community assembly, but in communities of saprotrophic and total fungi from soil samples, drift contributed less and its role was partially replaced by dispersal limitation. This study highlights the importance of climatic selection and stochastic processes on fungal community assembly in alpine regions, and emphasizes the significance of simultaneously investigating fungi with different trophic modes and from both roots and soils.

Sporocarp nutrition of ectomycorrhizal fungi indicates an important role for endemic species in a high productivity temperate rainforest

Endemic species of ectomycorrhizal fungi (EMF) are found throughout many biomes, but it is unclear whether their localized distribution is dictated by habitat filtering or geographical barriers to dispersal. We examined community composition (via long-read metabarcoding) and differences in sporocarp nutrition between endemic and cosmopolitan EMF species across perhumid temperate rainforests of British Columbia, characterized by soils with high nitrogen (N) supply alongside low phosphorus (P) and cation availability. Endemic EMF species, representing almost half of the community, had significantly greater sporocarp N (24% higher), potassium (+16%), and magnesium (+17%) concentrations than cosmopolitan species. Sporocarp P concentrations were comparatively low and did not differ by fungal range. However, sporocarp N% and P% were well correlated, supporting evidence for linkages in N and P acquisition. Endemics were more likely to occur on Tsuga heterophylla (a disjunct host genus) than Picea sitchensis (a circumpolar genus). The Inocybaceae and Thelephoraceae families had high proportions of endemic taxa, while species in Cortinariaceae were largely cosmopolitan, indicating some niche conservatism among genera. We conclude that superior adaptive traits in relation to perhumid soils were skewed toward the endemic community, underscoring the potentially important contribution of these localized fungi to rainforest nutrition and productivity.

Three new species in Russula subsection Xerampelinae supported by genealogical and phenotypic coherence

Xerampelinae is a subsection composed of species of ectomycorrhizal fungi belonging to the hyperdiverse and cosmopolitan genus Russula (Russulales). Species of Xerampelinae are recognized by their fishy or shrimp odor, browning context, and a green reaction to iron sulfate. However, species delimitation has traditionally relied on morphology and analysis of limited molecular data. Prior taxonomic work in Xerampelinae has led to the description of as many as 59 taxa in Europe and 19 in North America. Here we provide the first multilocus phylogeny of European and North American members based on two nrDNA loci and two protein-coding genes. The resulting phylogeny supports the recognition of 17 species-rank Xerampelinae clades; however, higher species richness (~23) is suggested by a more inclusive nuclear rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS barcode) analysis. Phylogenetic and morphological analyses support three new species with restricted geographic distributions: R. lapponica, R. neopascua, and R. olympiana. We confirm that the European species R. subrubens is present in North America and the North American species R. serissima (previously known as R. favrei) is present in Europe. Most other Xerampelinae appear restricted to either North America or Eurasia, which indicates a high degree of regional endemism; this includes R. xerampelina, a name widely applied to North American taxa, but a species restricted to Eurasia.

Contributions of ectomycorrhizal fungi in a reclaimed poplar forest (Populus yunnanensis) in an abandoned metal mine tailings pond, southwest China

Reclamation using fast-growing trees has great potential for agroforestry development on former non-ferrous metal mining areas. However, the functional traits of ectomycorrhizal fungi (ECMF) and the relationship between ECMF and reclaimed trees remain unknown. Here, the restoration of ECMF and their functions in reclaimed poplar (Populus yunnanensis) growing in a derelict metal mine tailings pond were investigated. We identified ECMF belonging to 15 genera in 8 families, suggesting the occurrence of spontaneous diversification as poplar reclamation progressed. We described a previously unknown ectomycorrhizal relationship between poplar roots and Bovista limosa. Our results showed that B. limosa PY5 alleviated the phytotoxicity of Cd and enhanced poplar heavy metal tolerance, resulting in increased plant growth due to reduced Cd accumulation in host tissues. As part of the improved metal tolerance mechanism, PY5 colonization activated antioxidant systems, enhanced the conversion of Cd into inactive chemical forms, and promoted the compartmentalization of Cd into host cell walls. These results suggest that introducing adaptative ECMF may be an alternative to bioaugmenting reforestation and phytomanagement programs of fast-growing native trees in the barren metal mining and smelting areas.

Systematic analysis of Russula in the North American Rocky Mountain alpine zone

Russula (Russulales) is an important ectomycorrhizal fungal genus in Arctic and alpine regions where it occurs with Salix, Betula, Dryas, and Polygonum, yet a complex phylogenetic analysis of the genus in these habitats is lacking. This research compared collections of Russula from the Rocky Mountain alpine (Colorado, Montana, Wyoming) with reference specimens from Arctic and alpine habitats, mostly in Europe, using an in-depth morphological study and a phylogenetic analysis of the nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS barcode) and the second largest subunit of the RNA polymerase II gene (rpb2). One hundred thirty-nine Russula collections were sequenced, including type material. Ten species are reported from alpine or treeline habitats in the Rocky Mountains. This is the first formal report of R. cf. altaica, R. saliceticola, and R. subrubens from the Rocky Mountains and of R. purpureofusca in North America. Russula laevis is reported for the first time under this name with a voucher, and not as an environmental sample. Previous reports of R. nana and R. laccata are molecularly confirmed. Two species are reported from subalpine habitats at treeline: R. montana with conifers and R. cf. altaica with Betula. In this study, R. laccata, R. subrubens, and R. laevis were collected in alpine habitats but have been reported below treeline in Europe; these species may also be present at lower elevations in North America. Most species have an intercontinental distribution and have been reported in other alpine or Arctic habitats. Two unidentified and potentially new species were only found in North America and are discussed. A key to the alpine Russulas of North America is provided.

Nodulose-spored Inocybe from the Rocky Mountain alpine zone molecularly linked to European and type specimens

Inocybe (Inocybaceae) is one of the most diverse ectomycorrhizal genera in arctic and alpine habitats where the primary hosts are Salix, Betula, and Dryas. Subgenus Inocybe is common in these habitats and typically characterized by the presence of thick-walled pleurocystidia. Here, we focus on species that have angular or nodulose spores. Historically, over 30 taxa from this group have been reported from arctic and alpine habitats. Many names have been synonymized, whereas molecular analysis has revealed new species. Nuc rDNA internal transcribed spacer ITS1-5.8S-ITS2 (ITS) sequence data of 26 type specimens in this group now allow for further taxonomic clarification and comparison across continents of disjunct populations. Here, we compare ITS sequence data and the D1-D2 portion of nuc 28S rDNA (28S) from Rocky Mountain specimens with those of types and European reference material. We report 10 species from the Rocky Mountain alpine zone, all of which are conspecific with known European boreal, montane, or alpine species, and four are described as new; all have intercontinental distributions. Nodulose-spored Inocybe taxa that occur in the Rocky Mountain alpine zone include I. alpinomarginata, sp. nov., I. arctica, I. giacomi, I. leonina, I. murina, sp. nov., I. occulta, I. paragiacomi, sp. nov., I. phaeocystidiosa, I. purpureobadia, and I. subgiacomi, sp. nov. Remarkably, these species occur at elevations up to 4000 m and at latitudes as low as 36°N, hundreds of miles from the Arctic, the European alpine, and original type localities. Distributions are explained in part by host distributions and historical glaciation patterns. A key and full descriptions for Rocky mountain species are provided to promote species recognition.

A phylogenetic and taxonomic revision of sequestrate Russulaceae in Mediterranean and temperate Europe

A comprehensive morphological and genetic study of type material and new collections of sequestrate Russulales species formerly belonging to the genera Arcangeliella, Elasmomyces, Gymnomyces, Hydnangium, Hymenogaster, Macowanites, Martellia, Secotium and Zelleromyces is here undertaken, for the purpose of providing a complete taxonomical revision of sequestrate Russulaceae species in the Mediterranean and temperate regions of Europe. As a result, seven distinct taxa in the genus Lactarius and 18 in the genus Russula are identified. Six of them are new species: L. populicola, L. subgiennensis, R. bavarica, R. candidissima, R. hobartiae and R. mediterraneensis, and seven represent new combinations: L. josserandii (≡ Zelleromyces josserandii), L. soehneri (≡ Hydnangium soehneri), R. candida (≡ Hydnangium candidum), R. cerea (≡ Hydnangium cereum), R. messapica var. messapicoides (≡ Macowanites messapicoides), R. meridionalis (≡ Zelleromyces meridionalis) and R. neuhoffii (≡ Hydnangium neuhoffii). Twenty-two of the 25 taxa are illustrated, while descriptions, microscopy images, as well as extensive information on the ecology, chorology and phylogeny for all taxa are provided. A key is further included to facilitate their identification.

The genus Hebeloma in the Rocky Mountain Alpine Zone

Numerous taxa of Hebeloma have been reported in association with Salix, Dryas, and Betula in arctic-alpine habitats. However, species are notoriously difficult to delineate because morphological features overlap, and previously there was little reliable molecular data available. Recent progress in ITS-sequencing within the genus, coupled with an extensive database of parametrically described collections, now allows comparisons between species and their distributions. Here we report 16 species of Hebeloma from the Rocky Mountain alpine zone from some of the lowest latitudes (latitude 36°–45°N) and highest elevations (3000–4000 m) for arctic-alpine fungi in the northern hemisphere. Twelve of these species have been reported from arctic-alpine habitats in Europe and Greenland and are now molecularly confirmed from the Middle and Southern Rockies, greatly expanding their distribution. These are: Hebelomaalpinum, H.aurantioumbrinum, H.dunense, H.hiemale, H.marginatulum, H.mesophaeum, H.nigellum, H.oreophilum, H.subconcolor, H.spetsbergense, H.vaccinum, and H.velutipes. Hebelomahygrophilum is known from subalpine habitats in Europe, but was never recorded in arctic-alpine ecology. Three species recorded from the Rockies, but as yet not reported from Europe, are H.alpinicola, H.avellaneum, and H.excedens. The last two have never previously been reported from an arctic-alpine habitat. For all three of these species, the holotypes have been studied morphologically and molecularly, and have been incorporated into the analysis.

Ecology of Alpine Macrofungi - Combining Historical with Recent Data

Historical datasets of living communities are important because they can be used to document creeping shifts in species compositions. Such a historical data set exists for alpine fungi. From 1941 to 1953, the Swiss geologist Jules Favre visited yearly the region of the Swiss National Park and recorded the occurring fruiting bodies of fungi >1 mm (so-called “macrofungi”) in the alpine zone. Favre can be regarded as one of the pioneers of alpine fungal ecology not least because he noted location, elevation, geology, and associated plants during his numerous excursions. However, some relevant information is only available in his unpublished field-book. Overall, Favre listed 204 fungal species in 26 sampling sites, with 46 species being previously unknown. The analysis of his data revealed that the macrofungi recorded belong to two major ecological groups, either they are symbiotrophs and live in ectomycorrhizal associations with alpine plant hosts, or they are saprotrophs and decompose plant litter and soil organic matter. The most frequent fungi were members of Inocybe and Cortinarius, which form ectomycorrhizas with Dryas octopetala or the dwarf alpine Salix species. The scope of the present study was to combine Favre's historical dataset with more recent data, either with the “SwissFungi” database or with data from major studies of the French and German Alps, and with the data from novel high-throughput DNA sequencing techniques of soils from the Swiss Alps. Results of the latter application revealed, that problems associated with these new techniques are manifold and species determination remains often unclear. At this point, the fungal taxa collected by Favre and deposited as exsiccata at the “Conservatoire et Jardin Botaniques de la Ville de Genève” could be used as a reference sequence dataset for alpine fungal studies. In conclusion, it can be postulated that new improved databases are urgently necessary for the near future, particularly, with regard to investigating fungal communities from alpine regions using new techniques.