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Studies of fungal communities through amplicon metagenomics in aquatic environments, particularly in freshwater ecosystems, are still relatively recent. Unfortunately, many of these water bodies are facing growing threats from human expansion, such as effluent discharge from various human activities. As a result, these effluents have the potential to significantly alter the characteristics of water bodies and, subsequently, impact the diversity of their resident microorganisms. In this context, our objective was to investigate whether the fungal community structure varies according to the presence of different anthropic disturbances. We expect (i) the diversity of fungi will be greater and (ii) more specific unique operational taxonomic units (OTUs) related to each ecotonal system will be found compared to other sites of a lagoon. The study was conducted in the Tramandaí Lagoon (subtropical southern Brazil) at four distinct sampling points (estuary, middle of the lagoon, crop field area, and near a residential area where the Tramandaí River flows into the lagoon). As expected, the estuary and residential zones, which are ecotones, exhibited greater fungal diversity and more specific OTUs compared to the middle of the lagoon and crop field area. Moreover, a substantial proportion of fungal taxa could not be identified at the genus level, with many only classified at the phylum level, indicating potential new lineages. These findings underscore our limited understanding of the subtropical freshwater mycobiota.

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Agaricus is a genus of fungi in the family Agaricaceae, with several highly priced edible and medicinal species. Here we describe Agaricus macrochlamys, a new species, in A. sect. Arvenses, sympatric and morphologically cryptic with the edible and medicinally cultivated mushroom, A. subrufescens. Phylogenetic analyses showed that A. macrochlamys is closely related to A. subrufescens, and that A. fiardii is a new synonym of A. subrufescens. Despite being morphologically cryptic, A. macrochlamys can be distinguished from A. subrufescens by several ITS and tef1α species-specific markers and a 4-bp insertion in the tef1α sequence. Furthermore, A. subrufescens is a cosmopolitan species, while A. macrochlamys distribution is so far restricted to Mexico, the Dominican Republic, and the United States.

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The impact of lead (Pb) pollution on native communities of arbuscular mycorrhizal fungi (AMF) was assessed in soil samples from the surroundings of an abandoned Pb smelting factory. To consider the influence of host identity, bulk soil surrounding plant roots soil samples of predominant plant species (Sorghum halepense, Bidens pilosa, and Tagetes minuta) growing in Pb-polluted soils and in an uncontaminated site were selected. Molecular diversity was assessed by sequencing the 18S rDNA region with primers specific to AMF (AMV4.5NF/AMDGR) using Illumina MiSeq. A total of 115 virtual taxa (VT) of AMF were identified in this survey. Plant species did not affect AMF diversity patterns. However, soil Pb content was negatively correlated with VT richness per sample. Paraglomeraceae and Glomeraceae were the predominant families while Acaulosporaceae, Ambisporaceae, Archaeosporaceae, Claroideoglomeraceae, Diversisporaceae, and Gigasporaceae were less abundant. Acaulosporaceae and Glomeraceae were negatively affected by soil Pb, but Paraglomeraceae relative abundance increased under increasing soil Pb content. Overall, 26 indicator taxa were identified; four of them were previously reported in Pb-polluted soils (VT060; VT222; VT004; VT380); and five corresponded to cultured spores of Scutellospora castaneae (VT041), Diversispora spp. and Tricispora nevadensis (VT060), Diversispora epigaea (VT061), Glomus proliferum (VT099), and Gl. indicum (VT222). Even though AMF were present in Pb-polluted soils, community structure was strongly altered via the differential responses of taxonomic groups of AMF to Pb pollution. These taxon-specific differences in tolerance to soil Pb content should be considered for future phytoremediation strategies based on the selection and utilization of native Glomeromycota.

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It is generally assumed that recruitment and expansion of alien species along elevation gradients are constrained by climate. But, if plants are not fully constrained by climate, their expansion could be facilitated or hindered by other factors such as biotic interactions. Here, we assessed the composition of arbuscular mycorrhizal fungi (AMF) in soils along an elevation gradient (i.e. 900 m, 1600 m, 2200 m and 2700 m a.s.l.) through a fungal DNA meta-barcoding approach. In addition, we studied in the greenhouse the effects of AMF on growth and phosphorous (P) nutrition of seedlings of the alien trees Gleditsia triacanthos, Ligustrum lucidum and Pyracantha angustifolia cultivated in soils from those elevations, spanning the elevation at which they already form monospecific stands (below 1450 m a.s.l.) and higher elevations, above their current range of distribution in montane ecosystems of Central Argentina. For comparison, we also included in the experiment the dominant native tree Lithraea molleoides that historically occurs below 1300 m a.s.l. Arbuscular mycorrhizal fungal community composition showed strong community turnover with increasing elevation. The effects of these AMF communities on plant growth and nutrition differed among native and alien trees. While P nutrition in alien species' seedlings was generally enhanced by AMF along the whole gradient, the native species benefited only from AMF that occur in soils from the elevation corresponding to its current altitudinal range of distribution. These results suggest that AMF might foster upper range expansion of these invasive trees over non-invaded higher elevations.

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Ectomycorrhizal (ECM) fungal associates of Alnus are relatively few in comparison with those associated with other tree hosts. The composition of ECM assemblages associated with Alnus seems to change very little across the Northern Hemisphere. However, Alnus-associated ECM assemblages from the Western United States, Mexico, and Argentina tend to differ from those in eastern North America and Europe, presumably due to their different biogeographic histories. Alnus glutinosa is a northern European species subjected to diverse environmental conditions. To address intrageneric host preference within two distantly related Alnus species (Alnus acuminata and A. glutinosa), we tested the ECM colonization on seedlings of both species inoculated with natural soil from A. acuminata forests. Two tomentelloid ECM fungi from A. acuminata natural soils were determined from the anatomotyping and molecular analysis. Both species colonized A. glutinosa seedlings and presented similar relative abundances. Additional soil sequence data from A. acuminata sites suggest that a variety of tomentelloid taxa occur, including several unidentified Tomentella lineages. Maximum-likelihood and Bayesian inference analyses based on internal transcribed spacer (ITS) sequences from various locations do not reflect associations of taxa based on their biogeographic origin, and clades are in general constituted by sequences from diverse regions, including South America, Mexico, USA, and Europe. Results illustrate the probable role of specific tomentelloid fungi in the early colonization of seedlings in A. acuminata forests as well as their importance in the structure of the ECM propagule community at the sites.

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The Yungas, a system of tropical and subtropical montane forests on the eastern slopes of the Andes, are extremely diverse and severely threatened by anthropogenic pressure and climate change. Previous mycological works focused on macrofungi (e.g. agarics, polypores) and mycorrhizae in Alnus acuminata forests, while fungal diversity in other parts of the Yungas has remained mostly unexplored. We carried out Ion Torrent sequencing of ITS2 rDNA from soil samples taken at 24 sites along the entire latitudinal extent of the Yungas in Argentina. The sampled sites represent the three altitudinal forest types: the piedmont (400-700 m a.s.l.), montane (700-1500 m a.s.l.) and montane cloud (1500-3000 m a.s.l.) forests. The deep sequence data presented here (i.e. 4 108 126 quality-filtered sequences) indicate that fungal community composition correlates most strongly with elevation, with many fungi showing preference for a certain altitudinal forest type. For example, ectomycorrhizal and root endophytic fungi were most diverse in the montane cloud forests, particularly at sites dominated by Alnus acuminata, while the diversity values of various saprobic groups were highest at lower elevations. Despite the strong altitudinal community turnover, fungal diversity was comparable across the different zonal forest types. Besides elevation, soil pH, N, P, and organic matter contents correlated with fungal community structure as well, although most of these variables were co-correlated with elevation. Our data provide an unprecedented insight into the high diversity and spatial distribution of fungi in the Yungas forests.

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