The ectomycorrhizal fungal community in a neotropical forest dominated by the endemic dipterocarp Pakaraimaea dipterocarpacea

Ectomycorrhizal fungal communities associated with Crocanthemum and Lechea (Cistaceae) in subtropical Florida sandhill habitats

Cistaceae are shrubs, subshrubs and herbs that often occur in stressful, fire-prone or disturbed environments and form ectomycorrhizal (ECM) associations with symbiotic fungi. Although some Cistaceae are long-lived shrubs that grow to significant size, others are herbaceous annuals or short-lived plants. Thus, Cistaceae are atypical ECM hosts that are fundamentally different in their biology from trees that are the more typically studied ECM hosts. The Mediterranean region is the center of diversity for Cistaceae and the ectomycorrhizal fungi associated with Cistaceae hosts have primarily been studied in Europe, North Africa, and the Middle East. Mediterranean Cistaceae often host diverse communities of ECM fungi, but they also act as hosts for some ECM fungi that putatively show host-specificity or strong host preference for Cistaceae (including species of Delastria, Hebeloma, Terfezia, and Tirmania). The ECM associations of Cistaceae in North America, however, remain highly understudied. Here we use fungal DNA metabarcoding to document the ectomycorrhizal fungal communities associated with Crocanthemum and Lechea (Cistaceae) in open, fire-prone sandhill habitats in north Florida. At each site we also sampled nearby Pinus to determine whether small, herbaceous Cistaceae have specialized ECM fungi or whether they share their ECM fungal community with nearby pines. The ECM communities of Florida Cistaceae are dominated by Cenococcum (Ascomycota) and Russula (Basidiomycota) species but were also significantly associated with Delastria, an understudied genus of mostly truffle-like Pezizales (Ascomycota). Although many Cistaceae ECM fungi were shared with neighboring pines, the ECM communities with Cistaceae were nonetheless significantly different than those of pines.

New Cortinariaceae species associated with Dicymbe, Aldina, and Pakaraimaea in Guyana

Species of the ectomycorrhizal (ECM) family Cortinariaceae (Agaricales, Agaricomycetes, Basidiomycota) have long been considered impoverished or absent from lowland tropical rainforests. Several decades of collecting in forests dominated by ECM trees in South America's Guiana Shield is countering this view, with discovery of numerous Cortinariaceae species. To date, ~12 morphospecies of this family have been found in the central Pakaraima Mountains of Guyana. Here, we describe three of these as new species of Cortinarius and two as new species of Phlegmacium from forests dominated by the ECM tree genera Dicymbe (Fabaceae subfam. Detarioideae), Aldina (Fabaceae subfam. Papilionoideae), and Pakaraimaea (Cistaceae). Macromorphological, micromorphological, habitat, and DNA sequence data are provided for each new species.

Extreme specificity in obligate mutualism-A role for competition?

Obligate mutualisms, reciprocally obligate beneficial interactions, are some of the most important mutualisms on the planet, providing the basis for the evolution of the eukaryotic cell, the formation and persistence of terrestrial ecosystems and the establishment and expansion of coral reefs. In addition, these mutualisms can also lead to the diversification of interacting partner species. Accompanying this diversification is a general pattern of a high degree of specificity among interacting partner species. A survey of obligate mutualisms demonstrates that greater than half of these systems have only one or two mutualist species on each side of the interaction. This is in stark contrast to facultative mutualisms that can have dozens of interacting mutualist species. We posit that the high degree of specificity in obligate mutualisms is driven by competition within obligate mutualist guilds that limits species richness. Competition may be particularly potent in these mutualisms because mutualistic partners are totally dependent on each other's fitness gains, which may fuel interspecific competition. Theory and the limited number of empirical studies testing for the role of competition in determining specificity suggest that competition may be an important force that fuels the high degree of specificity. Further empirical research is needed to dissect the relative roles of trait complementarity, mutualism regulation, and competition among mutualist guild members in determining mutualism specificity at local scales.

Boletaceae in China: Taxonomy and phylogeny reveal a new genus, two new species, and a new record

Boletaceae, the largest family in Boletales, has been attracted by mycologists in the world due to its diverse morphology and complex history of evolution. Although considerable work has been done in the past decades, novel taxa are continually described. The current study aimed to introduce three new taxa and one new record of Boletaceae from China. The morphological descriptions, color photographs, phylogenetic trees to show the positions of the taxa, and comparisons with allied taxa are provided. The new genus Hemilanmaoa is unique in the Pulveroboletus group, and Hemilanmaoa retistipitatus was introduced as the type species. It can be distinguished by its bluing basidioma when injured, a decurrent hymenophore, a stipe covered with distinct reticulations, and a fertile stipitipellis. Porphyrellus pseudocyaneotinctus is characterized by its pileipellis consisting of broadly concatenated cells and thin-walled caulocystidia in Porphyrellus. In Phylloporus, Phylloporus biyangensis can be distinguished by its hymenophores that change to blue when injured and yellow basal mycelium. Lanmaoa angustispora, as a new record, is first reported in Northern China. Internal transcribed spacer (ITS), 28S rDNA (28S), translation elongation factor 1-alpha (tef1-α), RNA polymerase II subunit 1 (rpb1), and RNA polymerase II subunit 2 (rpb2) were employed to execute phylogenetic analyses.

Neotropical Clavulina: Two new species from Mexico and a re-evaluation of Clavulina floridana

Clavulina comprises ca. 90 described species distributed worldwide in both tropical and temperate regions. However, only one species (C. floridana) has been described so far from tropical North America. We used morphological and molecular data from three DNA loci (nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 [ITS], a portion of nuc 28S rDNA [28S], and a fragment of DNA-directed RNA polymerase II second largest subunit [RPB2]) from basidiomata and ectomycorrhizas collected in tropical ecosystems from three biogeographic provinces of Mexico and one tropical province in the USA to investigate the phylogenetic and taxonomic diversity of Clavulina in the region. Nine new species-level clades were discovered, two of which are proposed as new species (C. arboreiparva and C. tuxtlasana). Specimens of C. floridana recently collected in Florida were included in our analyses, for which a modern description is provided. In addition, C. floridana is a new record for Mexico. The diversity of Clavulina in tropical North America is comparable to that found in lowland tropical South America. However, some of the species found in tropical deciduous forests produce small, rare, and inconspicuous basidiomata, which easily go unnoticed, and therefore are poorly represented in collections. Many species remain undescribed in tropical regions of North America.

Russulaceae of the Pakaraima Mountains of Guyana. IV. New species forming a distinct lineage of Lactarius subg. Plinthogalus

The Neotropics have recently emerged as an important region for studies of tropical ectomycorrhizal (ECM) fungi. Specific neotropical areas with high ECM host tree densities have ECM fungal diversities rivaling those of higher-latitude forests. Some forests of the Guiana Shield are dominated by endemic ECM trees of the Fabaceae, including species of Dicymbe (subfam. Detarioideae), Aldina (subfam. Papilionoideae), and Pakaraimaea (Cistaceae). One of the most species-rich ECM fungal families present in each of these systems is Russulaceae. Long-term sampling in forests in Guyana's Pakaraima Mountains has revealed a number of species of the Russulaceae genera Lactarius, Lactifluus, and Russula. In this study, we document a previously unknown, distinct lineage of Lactarius subg. Plinthogalus containing eight species from the Guiana Shield. Here, we describe five of these species from Guyana as new to science: Lactarius humiphilus, Lactarius mycenoides, Lactarius guyanensis, Lactarius dicymbophilus, and Lactarius aurantiolamellatus. Morphological descriptions, habit, habitat, and known distribution are provided for each new species. Sequence data for the barcode internal transcribed spacer (ITS) locus are provided for types and most other collections of the new taxa, and a molecular phylogenetic analysis based on the ITS, 28S, and RPB2 (second-largest subunit of the RNA polymerase II) loci across the genus Lactarius corroborates their morphology-based infrageneric placement. The discovery of this lineage changes our insights into the biogeography and evolutionary history of Lactarius subg. Plinthogalus.

Biogeographic history of a large clade of ectomycorrhizal fungi, the Russulaceae, in the Neotropics and adjacent regions

The biogeography of neotropical fungi remains poorly understood. Here, we reconstruct the origins and diversification of neotropical lineages in one of the largest clades of ectomycorrhizal fungi in the globally widespread family Russulaceae. We inferred a supertree of 3285 operational taxonomic units, representing worldwide internal transcribed spacer sequences. We reconstructed biogeographic history and diversification and identified lineages in the Neotropics and adjacent Patagonia. The ectomycorrhizal Russulaceae have a tropical African origin. The oldest lineages in tropical South America, most with African sister groups, date to the mid-Eocene, possibly coinciding with a boreotropical migration corridor. There were several transatlantic dispersal events from Africa more recently. Andean and Central American lineages mostly have north-temperate origins and are associated with North Andean uplift and the general north-south biotic interchange across the Panama isthmus, respectively. Patagonian lineages have Australasian affinities. Diversification rates in tropical South America and other tropical areas are lower than in temperate areas. Neotropical Russulaceae have multiple biogeographic origins since the mid-Eocene involving dispersal and co-migration. Discontinuous distributions of host plants may explain low diversification rates of tropical lowland ectomycorrhizal fungi. Deeply diverging neotropical fungal lineages need to be better documented.

Multi-Gene Phylogenetic Approach for Identification and Diversity Analysis of Bipolaris maydis and Curvularia lunata Isolates Causing Foliar Blight of Zea mays

Bipolaris species are known to be important plant pathogens that commonly cause leaf spot, root rot, and seedling blight in a wide range of hosts worldwide. In 2017, complex symptomatic cases of maydis leaf blight (caused by Bipolaris maydis) and maize leaf spot (caused by Curvularia lunata) have become increasingly significant in the main maize-growing regions of India. A total of 186 samples of maydis leaf blight and 129 maize leaf spot samples were collected, in 2017, from 20 sampling sites in the main maize-growing regions of India to explore the diversity and identity of this pathogenic causal agent. A total of 77 Bipolaris maydis isolates and 74 Curvularia lunata isolates were screened based on morphological and molecular characterization and phylogenetic analysis based on ribosomal markers-nuclear ribosomal DNA (rDNA) internal transcribed spacer (ITS) region, 28S nuclear ribosomal large subunit rRNA gene (LSU), D1/D2 domain of large-subunit (LSU) ribosomal DNA (rDNA), and protein-coding gene-glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Due to a dearth of molecular data from ex-type cultures, the use of few gene regions for species resolution, and overlapping morphological features, species recognition in Bipolaris has proven difficult. The present study used the multi-gene phylogenetic approach for proper identification and diversity of geographically distributed B. maydis and C. lunata isolates in Indian settings and provides useful insight into and explanation of its quantitative findings.

Hemiaustroboletus, a new genus in the subfamily Austroboletoideae (Boletaceae, Boletales)

The present study describes Hemiaustroboletusgen. nov. in the subfamily Austroboletoideae (Boletaceae). Hemiaustroboletus is supported by morphological and molecular data using LSU and RPB2 regions. Additionally, its geographic distribution and intraspecific variation were inferred using ITS sequences. The genus is characterised by pileate-stipitate basidiomata; purple, brown, reddish-brown, orange-brown to dark brown vinaceous pileus; whitish or lilac to vinaceous context and a subclavate stipe. Microscopically, it is characterised by ornamented, slightly verrucose, cracked to perforated brown basidiospores. Two species are described within the genus, Hemiaustroboletus vinaceobrunneussp. nov. and H. vinaceussp. nov.Hemiaustroboletus vinaceussp. nov. is morphologically similar to Austroboletus gracilis, which suggests they may have been confused in the past. This study presents the phylogenetic placement, microscopic structures, detailed morphological descriptions and illustrations of both new species.

Diversity and Phylogeny of Novel Cord-Forming Fungi from Borneo

Cord-forming (CF) fungi are found worldwide; however, tropical CF fungi are poorly documented. They play an essential role in forest ecosystems by interconnecting nutrient resources and aiding in the decomposition of plant matter and woody litter. CF fungi samples were collected from two forest conservation sites in the Sabah region of Malaysian Borneo. Sequencing and phylogenetic analysis of the ribosomal rRNA gene array 18S to 28S region from cords collected placed all of the collected specimens in Agaricomycetes (Basidiomycetes), specifically within the orders Trechisporales, Phallales, Hymenochaetales, Polyporales, and Agaricales. Comparison of the cord-derived sequences against GenBank and UNITE sequence databases, as well as phylogenetic analyses, revealed they were all novel sequences types. Many of these novel lineages were found to be closely related to other basidiomycetes commonly found in tropical forests, suggesting a large undiscovered tropical fungal diversity in Borneo that has been detected independently of sampling fruiting bodies. We show how these sequence types relate to the morphologies of the cords from which they were sampled. We also highlight how rapid, small-scale sampling can be a useful tool as an easy and relatively unbiased way of collecting data on cord-forming fungi in difficult-to-access, complex forest environments, independently of locating and sampling sporophores.

Limited contributions of plant pathogens to density-dependent seedling mortality of mast fruiting Bornean trees

Fungal pathogens are implicated in driving tropical plant diversity by facilitating strong, negative density-dependent mortality of conspecific seedlings (C-NDD). Assessment of the role of fungal pathogens in mediating coexistence derives from relatively few tree species and predominantly the Neotropics, limiting our understanding of their role in maintaining hyper-diversity in many tropical forests. A key question is whether fungal pathogen-mediated C-NDD seedling mortality is ubiquitous across diverse plant communities. Using a manipulative shadehouse experiment, we tested the role of fungal pathogens in mediating C-NDD seedling mortality of eight mast fruiting Bornean trees, typical of the species-rich forests of South East Asia. We demonstrate species-specific responses of seedlings to fungicide and density treatments, generating weak negative density-dependent mortality. Overall seedling mortality was low and likely insufficient to promote overall community diversity. Although conducted in the same way as previous studies, we find little evidence that fungal pathogens play a substantial role in determining patterns of seedling mortality in a SE Asian mast fruiting forest, questioning our understanding of how Janzen-Connell mechanisms structure the plant communities of this globally important forest type.

Amanita in the Guineo-Congolian rainforest: Epitypes and new species from the Dja Biosphere Reserve, Cameroon

Four epitypes and three new species of Amanita (Amanitaceae, Agaricales, Agaricomycetes, Basidiomycota) are described from Guineo-Congolian rainforests of Cameroon. Amanita echinulata, A. fulvopulverulenta, A. robusta, and A. bingensis are epitypified based on collections that are the first since the species were described nearly a century ago. Morphological features of the epitypes are described and enumerated. Amanita minima, Amanita luteolamellata, and A. goossensfontanae are described as new and added to the known macromycota of tropical Africa. Habit, habitat, and known distribution are provided for each species. Sequence data for the internal transcribed spacer (ITS) locus are provided for types and other collections of all taxa, and a molecular phylogenetic analysis across the genus Amanita corroborates morphology-based infrageneric placement for each.

Yeast in plant phytotelmata: Is there a "core" community in different localities of rupestrian savannas of Brazil?

Ephemeral microbial communities usually undergo priority effect and result in higher diversity with a few representatives of each species. Community structure of yeasts in bromeliad tanks was compared between two rupestrian savanna (Cerrado) areas in Brazil and to yeasts isolated from water holes in the same areas. Water samples were collected from 60 tanks of bromeliads Bromelia karatas and Encholirium sp. and rock holes at the Karstic Area of Aurora, Tocantins State and 60 tanks of Vriesea minarum (Bromeliaceae) and Paepalanthus bromelioides (Eriocaulaceae) at Serra do Cipó National Park, Minas Gerais State in Brazil. The yeast diversity comprised 90 species from which 60% are basidiomycetous yeasts usually associated with phylloplane, soils, and aquatic habitats. The species Papiliotrema laurentii, Rhodotorula mucilaginosa, Pa. nemorosus, and Pseudozyma hubeiensis were the most frequent species associated with bromeliads. Eighteen yeast species, two ascomycetous and 16 basidiomycetous, were consistently isolated from the substrates in both areas and may represent a core community in bromeliads in rupestrian fields. Singlets occurred in 38 to 69% of samples, and 32 species were isolated only once. Our findings reinforce the ephemeral nature of the yeast communities associated with tank-forming plants in which individual phytotelmata act as patches or aquatic islands prone to rapid colonization-extinction rates receiving inocula from plant and soil debris. Ephemeral rock holes also represent a transitory habitat for yeast species associated with plants and soil.

Longistriata flava (Boletaceae, Basidiomycota) - a new monotypic sequestrate genus and species from Brazilian Atlantic Forest

A new monotypic sequestrate genus, Longistriata is described based on collections from the Neotropical forest of Atlantic forest in Paraíba, Northeast Brazil – an area known for its high degree of endemism. The striking features of this new fungus are the hypogeous habit, the vivid yellow peridium in mature basidiomes, broadly ellipsoid basidiospores with a distinct wall that is ornamented with longitudinal striations and lageniform cystidia with rounded apices. Phylogenetic analysis, based on LSU and tef-1α regions, showed that the type species, Longistriataflava, is phylogenetically sister to the monotypic sequestrate African genus Mackintoshia in Boletaceae. Together these two species formed the earliest diverging lineage in the subfamily Zangioideae. Longistriataflava is found in nutrient-poor white sand habitats where plants in the genera Coccoloba (Polygonaceae) and Guapira (Nyctaginaceae) are the only potential ectomycorrhizal host symbionts.

Notes, outline and divergence times of Basidiomycota

The Basidiomycota constitutes a major phylum of the kingdom Fungi and is second in species numbers to the Ascomycota. The present work provides an overview of all validly published, currently used basidiomycete genera to date in a single document. An outline of all genera of Basidiomycota is provided, which includes 1928 currently used genera names, with 1263 synonyms, which are distributed in 241 families, 68 orders, 18 classes and four subphyla. We provide brief notes for each accepted genus including information on classification, number of accepted species, type species, life mode, habitat, distribution, and sequence information. Furthermore, three phylogenetic analyses with combined LSU, SSU, 5.8s, rpb1, rpb2, and ef1 datasets for the subphyla Agaricomycotina, Pucciniomycotina and Ustilaginomycotina are conducted, respectively. Divergence time estimates are provided to the family level with 632 species from 62 orders, 168 families and 605 genera. Our study indicates that the divergence times of the subphyla in Basidiomycota are 406–430 Mya, classes are 211–383 Mya, and orders are 99–323 Mya, which are largely consistent with previous studies. In this study, all phylogenetically supported families were dated, with the families of Agaricomycotina diverging from 27–178 Mya, Pucciniomycotina from 85–222 Mya, and Ustilaginomycotina from 79–177 Mya. Divergence times as additional criterion in ranking provide additional evidence to resolve taxonomic problems in the Basidiomycota taxonomic system, and also provide a better understanding of their phylogeny and evolution.

Rarity of monodominance in hyperdiverse Amazonian forests

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such “monodominant” forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors.

Ectomycorrhizal associations in the tropics - biogeography, diversity patterns and ecosystem roles

Contents Summary 1076 I. Introduction 1076 II. Historical overview 1077 III. Identities and distributions of tropical ectomycorrhizal plants 1077 IV. Dominance of tropical forests by ECM trees 1078 V. Biogeography of tropical ECM fungi 1081 VI. Beta diversity patterns in tropical ECM fungal communities 1082 VII. Conclusions and future research 1086 Acknowledgements 1087 References 1087 SUMMARY: Ectomycorrhizal (ECM) associations were historically considered rare or absent from tropical ecosystems. Although most tropical forests are dominated by arbuscular mycorrhizal (AM) trees, ECM associations are widespread and found in all tropical regions. Here, we highlight emerging patterns of ECM biogeography, diversity and ecosystem functions, identify knowledge gaps, and offer direction for future research. At the continental and regional scales, tropical ECM systems are highly diverse and vary widely in ECM plant and fungal abundance, diversity, composition and phylogenetic affinities. We found strong regional differences among the dominant host plant families, suggesting that biogeographical factors strongly influence tropical ECM symbioses. Both ECM plants and fungi also exhibit strong turnover along altitudinal and soil fertility gradients, suggesting niche differentiation among taxa. Ectomycorrhizal fungi are often more abundant and diverse in sites with nutrient-poor soils, suggesting that ECM associations can optimize plant nutrition and may contribute to the maintenance of tropical monodominant forests. More research is needed to elucidate the diversity patterns of ECM fungi and plants in the tropics and to clarify the role of this symbiosis in nutrient and carbon cycling.

New species of Amanita subgen. Lepidella from Guyana

New species of Amanita subgen. Lepidella are described from Guyana. Amanita cyanochlorinosma sp. nov., Amanita fulvoalba sp. nov., and Amanita guyanensis sp. nov. represent the latest additions to the growing body of newly described ectomycorrhizal fungi native to Dicymbe-dominated tropical rainforests. Macro- and micromorphological characters, habitat, and DNA sequence data for the ITS, nrLSU, rpb2, and ef1-α are provided for each taxon, and β-tubulin for most. Distinctive morphological features warrant the recognition of the three new species and a molecular phylogenetic analysis of taxa across Amanita subgen. Lepidella corroborates their infrageneric placements.

Ectomycorrhizal Communities Associated with the Legume Acacia spirorbis Growing on Contrasted Edaphic Constraints in New Caledonia

This study aims to characterize the ectomycorrhizal (ECM) communities associated with Acacia spirorbis, a legume tree widely spread in New Caledonia that spontaneously grows on contrasted edaphic constraints, i.e. calcareous, ferralitic and volcano-sedimentary soils. Soil geochemical parameters and diversity of ECM communities were assessed in 12 sites representative of the three mains categories of soils. The ectomycorrhizal status of Acacia spirorbis was confirmed in all studied soils, with a fungal community dominated at 92% by Basidiomycota, mostly represented by/tomentella-thelephora (27.6%), /boletus (15.8%), /sebacina (10.5%), /russula-lactarius (10.5%) and /pisolithus-scleroderma (7.9%) lineages. The diversity and the proportion of the ECM lineages were similar for the ferralitic and volcano-sedimentary soils but significantly different for the calcareous soils. These differences in the distribution of the ECM communities were statistically correlated with pH, Ca, P and Al in the calcareous soils and with Co in the ferralitic soils. Altogether, these data suggest a high capacity of A. spirorbis to form ECM symbioses with a large spectrum of fungi regardless the soil categories with contrasted edaphic parameters.

First record of in vitro formation of ectomycorrhizae in Psidium cattleianum Sabine, a native Myrtaceae of the Brazilian Atlantic Forest

Like many other species of trees native to the Brazilian Mata Atlântica (Atlantic Forest), the Myrtaceae, such as the Red Araza (Psidium cattleianum Sabine), are widely cited as arbuscular mycorrhizal formers. Nevertheless, recent studies show evidence that Myrtaceae from different tropical, subtropical and neotropical ecosystems can also prompt the formation of ectomycorrhizae, indicating that this species' ectomycorrhizal status should be further explored. Because of this, this research effort studied the in vitro interaction between the Red Araza and two ectomycorrhizal fungi isolates, belonging to the Pisolithus microcarpus (D17) and Scleroderma citrinum (UFSC-Sc133) species. An analysis was performed to determine the formation of ectomycorrhizal structures, or lack thereof, and the developmental differences between the in vitro mycorrhized and non-mycorrhized plants. The analysis proved that indeed an ectomycorrhizal association was developed between the Red Araza, and the D17 and UFSC-Sc133 isolates, a fact never before registered in the existing literature. After an in vitro period of 110 days, it was confirmed that the D17 and UFSC-Sc133 isolates formed mycorrhizal colonization of 91.6% and 15.7%, respectively. Furthermore, both isolates also promoted root thickening, and the formation of a fungal mantle and a Hartig net. However, when compared to the Control plants, the fungal isolates did not contribute to an increase in the development of the subject plants, possibly due to the specific experimental conditions used, such as a high humidity environment and high availability of nutrients in the symbiotic substrate.

Soil abiotic variables are more important than Salicaceae phylogeny or habitat specialization in determining soil microbial community structure

Predicting the outcome of interspecific interactions is a central goal in ecology. The diverse soil microbes that interact with plants are shaped by different aspects of plant identity, such as phylogenetic history and functional group. Species interactions may also be strongly shaped by abiotic environment, but there is mixed evidence on the relative importance of environment, plant identity and their interactions in shaping soil microbial communities. Using a multifactor, split-plot field experiment, we tested how hydrologic context, and three facets of Salicaceae plant identity-habitat specialization, phylogenetic distance and species identity-influence soil microbial community structure. Analysis of microbial community sequencing data with generalized dissimilarity models showed that abiotic environment explained up to 25% of variation in community composition of soil bacteria, fungi and archaea, while Salicaceae identity influenced <1% of the variation in community composition of soil microbial taxa. Multivariate linear models indicated that the influence of Salicaceae identity was small, but did contribute to differentiation of soil microbes within treatments. Moreover, results from a microbial niche breadth analysis show that soil microbes in wetlands have more specialized host associations than soil microbes in drier environments-showing that abiotic environment changed how plant identity correlated with soil microbial communities. This study demonstrates the predominance of major abiotic factors in shaping soil microbial community structure; the significance of abiotic context to biotic influence on soil microbes; and the utility of field experiments to disentangling the abiotic and biotic factors that are thought to be most essential for soil microbial communities.

Basidiospores attach to the seed of Shorea leprosula in lowland tropical dipterocarp forest and form functional ectomycorrhiza on seed germination

This research aimed to study the ectomycorrhiza formed by basidiospores attached to the outer surface of Shorea leprosula (Dipterocarpaceae) seed collected from a lowland tropical dipterocarp forest. Two groups of seeds were collected: control seeds collected from plastic net hanging 2 m above the ground and forest floor seeds collected on the forest floor. Before planting, 15 seeds from each group were observed for basidiospores attached to the seed. Ten of the 3-week-old S. leprosula seedlings of each group were individually grown in 1.5 kg of sterile zeolite for 8 months in a greenhouse. Pots were fertilized with MMN solution containing half the strength of phosphate. Fungal identity, ectomycorrhizal root tip colonization and anatomy, plant growth, and phosphate uptake were measured. The control seeds did not have basidiospores attached, whereas the forest floor seeds had 2 × 10⁵ basidiospores of Tomentella. Bioassay test results indicate that the seedlings from the control seeds did not form ectomycorrhiza, whereas those seedlings from the forest floor seeds formed 3 morphotypes of ectomycorrhizae. Based on ITS1, 5.8S, and ITS2 rDNA region analyses, the 3 morphotypes belonged to Tomentella sp. HBT2, Tomentella sp. HBT4, and Scleroderma sp. HBS3. Root colonization percentage was above 70% for all three morphotypes. Root colonization in general increased plant growth and phosphate uptake. This is the first report of Tomentella basidiospores attached on the seed surface as a functional inoculum and of Tomentella ectomycorrhiza from dipterocarps lowland tropical forest.

Investigating niche partitioning of ectomycorrhizal fungi in specialized rooting zones of the monodominant leguminous tree Dicymbe corymbosa

Temperate ectomycorrhizal (ECM) fungi show segregation whereby some species dominate in organic layers and others favor mineral soils. Weak layering in tropical soils is hypothesized to decrease niche space and therefore reduce the diversity of ectomycorrhizal fungi. The Neotropical ECM tree Dicymbe corymbosa forms monodominant stands and has a distinct physiognomy with vertical crown development, adventitious roots and massive root mounds, leading to multi-stemmed trees with spatially segregated rooting environments: aerial litter caches, aerial decayed wood, organic root mounds and mineral soil. We hypothesized that these microhabitats host distinct fungal assemblages and therefore promote diversity. To test our hypothesis, we sampled D. corymbosa ectomycorrhizal root tips from the four microhabitats and analyzed community composition based on pyrosequencing of fungal internal transcribed spacer (ITS) barcode markers. Several dominant fungi were ubiquitous but analyses nonetheless suggested that communities in mineral soil samples were statistically distinct from communities in organic microhabitats. These data indicate that distinctive rooting zones of D. corymbosa contribute to spatial segregation of the fungal community and likely enhance fungal diversity.

Dimensions of biodiversity in the Earth mycobiome

Fungi represent a large proportion of the genetic diversity on Earth and fungal activity influences the structure of plant and animal communities, as well as rates of ecosystem processes. Large-scale DNA-sequencing datasets are beginning to reveal the dimensions of fungal biodiversity, which seem to be fundamentally different to bacteria, plants and animals. In this Review, we describe the patterns of fungal biodiversity that have been revealed by molecular-based studies. Furthermore, we consider the evidence that supports the roles of different candidate drivers of fungal diversity at a range of spatial scales, as well as the role of dispersal limitation in maintaining regional endemism and influencing local community assembly. Finally, we discuss the ecological mechanisms that are likely to be responsible for the high heterogeneity that is observed in fungal communities at local scales.

Transfer to forest nurseries significantly affects mycorrhizal community composition of Asteropeia mcphersonii wildings

Mycorrhizal symbiosis is extremely important for tree growth, survival and resistance after transplantation particularly in Madagascar where deforestation is a major concern. The importance of mycorrhizal symbiosis is further increased when soil conditions at the planting site are limiting. To identify technical itineraries capable of improving ecological restoration in Madagascar, we needed to obtain native ectomycorrhizal (ECM) saplings with a wide diversity of ECM fungi. To this end, we transplanted ECM seedlings from the wild (wildlings) to a nursery. Using molecular characterisation of internal transcribed spacer (ITS) rDNA, we tested the effect of transplanting Asteropeia mcphersonii wildlings on ECM communities after 8 months of growth in the nursery. With or without the addition of soil from the site where the seedlings were sampled to the nursery substrate, we observed a dramatic change in the composition of fungal communities with a decrease in the ECM infection rate, a tremendous increase in the abundance of an operational taxonomic unit (OTU) taxonomically close to the order Trechisporales and the disappearance of all OTUs of Boletales. Transplanting to the nursery and/or to nursery conditions was shown to be incompatible with the survival and even less with the development in the nursery of most ECM fungi naturally associated with A. mcphersonii wildings.

Guyanagarika, a new ectomycorrhizal genus of Agaricales from the Neotropics

A new genus and three new species of Agaricales are described from the Pakaraima Mountains of Guyana in the central Guiana Shield. All three of these new species fruit on the ground in association with species of the ectomycorrhizal (ECM) tree genus Dicymbe (Fabaceae subfam. Caesalpinioideae) and one species has been shown to form ectomycorrhizas. Multi-locus molecular phylogenetic analyses place Guyanagarika gen. nov. within the Catathelasma clade, a lineage in the suborder Tricholomatineae of the Agaricales. We formally recognize this 'Catathelasma clade' as an expanded family Catathelasmataceae that includes the genera Callistosporium, Catathelasma, Guyanagarika, Macrocybe, Pleurocollybia, and Pseudolaccaria. Within the Catathelasmataceae, Catathelasma and Guyanagarika represent independent origins of the ectomycorrhizal habit. Guyanagarika is the first documented case of an ECM Agaricales genus known only from the Neotropics.

New species of Elaphomyces (Elaphomycetaceae, Eurotiales, Ascomycota) from tropical rainforests of Cameroon and Guyana

The sequestrate false truffles Elaphomyces favosus, E. iuppitercellus, and E. labyrinthinus spp. nov. are described as new to science from the Dja Biosphere Reserve, Cameroon. Elaphomyces adamizans sp. nov. is described as new from the Pakaraima Mountains of Guyana. The Cameroonian species are the first Elaphomyces taxa to be formally described from Africa, occurring in lowland Guineo-Congolian tropical rainforests dominated by the ectomycorrhizal (ECM) canopy tree Gilbertiodendron dewevrei (Fabaceae subfam. Caesalpinioideae). The Guyanese species is the third to be discovered in lowland tropical South America, occurring in forests dominated by the ECM trees Pakaraimaea dipterocarpacea (Dipterocarpaceae) and Dicymbe jenmanii (Fabaceae subfam. Caesalpinioideae). Macromorphological, micromorphological, habitat, and DNA sequence data are provided for each new species. Molecular and morphological data place these fungi in Elaphomycetaceae (Eurotiales, Ascomycota). Unique morphological features are congruent with molecular delimitation of each of the new species based on a phylogenetic analysis of the rDNA ITS and 28S loci across the Elaphomycetaceae. The phylogenetic analysis also suggests that a common ancestor is shared between some Elaphomyces species from Africa and South America, and that species of the stalked, volvate genus Pseudotulostoma may be nested in Elaphomyces.

Variation in ectomycorrhizal fungal communities associated with Oreomunnea mexicana (Juglandaceae) in a Neotropical montane forest

Neotropical montane forests are often dominated by ectomycorrhizal (EM) tree species, yet the diversity of their EM fungal communities remains poorly explored. In lower montane forests in western Panama, the EM tree species Oreomunnea mexicana (Juglandaceae) forms locally dense populations in forest otherwise characterized by trees that form arbuscular mycorrhizal (AM) associations. The objective of this study was to compare the composition of EM fungal communities associated with Oreomunnea adults, saplings, and seedlings across sites differing in soil fertility and the amount and seasonality of rainfall. Analysis of fungal nrITS DNA (nuclear ribosomal internal transcribed spacers) revealed 115 EM fungi taxa from 234 EM root tips collected from adults, saplings, and seedlings in four sites. EM fungal communities were equally species-rich and diverse across Oreomunnea developmental stages and sites, regardless of soil conditions or rainfall patterns. However, ordination analysis revealed high compositional turnover between low and high fertility/rainfall sites located ca. 6 km apart. The EM fungal community was dominated by Russula (ca. 36 taxa). Cortinarius, represented by 14 species and previously reported to extract nitrogen from organic sources under low nitrogen availability, was found only in low fertility/high rainfall sites. Phylogenetic diversity analyses of Russula revealed greater evolutionary distance among taxa found on sites with contrasting fertility and rainfall than was expected by chance, suggesting that environmental differences among sites may be important in structuring EM fungal communities. More research is needed to evaluate whether EM fungal taxa associated with Oreomunnea form mycorrhizal networks that might account for local dominance of this tree species in otherwise diverse forest communities.

New Boletaceae taxa from Guyana: Binderoboletus segoi gen. and sp. nov., Guyanaporus albipodus gen. and sp. nov., Singerocomus rubriflavus gen. and sp. nov., and a new combination for Xerocomus inundabilis

Binderoboletus segoi gen. and sp. nov., Guyanaporus albipodus gen. and sp. nov. and Singerocomus rubriflavus gen. and sp. nov. (Boletaceae, Boletales, Basidiomycota) are described from the Pakaraima Mountains and adjacent lowlands of Guyana. Xerocomus inundabilis, originally described from the central Brazilian Amazon and based solely on the type collection, is redescribed from numerous collections from Guyana and transferred into Singerocomus. These boletes occur in Neotropical forests dominated by ectomycorrhizal trees in the genera Dicymbe (Fabaceae subfam. Caesalpinioideae), Aldina (Fabaceae subfam. Papilionoideae) and Pakaraimaea (Dipterocarpaceae). Three of the species were repeatedly found in a multiyear sporocarp survey in Dicymbe corymbosa-monodominant forest. Macromorphological, micromorphological, habitat and multilocus DNA sequence data are provided for each species. A molecular phylogenetic analysis based on a large taxon set across the Boletaceae justifies erection of the new genera.

New sequestrate fungi from Guyana: Jimtrappea guyanensis gen. sp. nov., Castellanea pakaraimophila gen. sp. nov., and Costatisporus cyanescens gen. sp. nov. (Boletaceae, Boletales)

Jimtrappea guyanensis gen. sp. nov., Castellanea pakaraimophila gen. sp. nov., and Costatisporus cyanescens gen. sp. nov. are described as new to science. These sequestrate, hypogeous fungi were collected in Guyana under closed canopy tropical forests in association with ectomycorrhizal (ECM) host tree genera Dicymbe (Fabaceae subfam. Caesalpinioideae), Aldina (Fabaceae subfam. Papilionoideae), and Pakaraimaea (Dipterocarpaceae). Molecular data place these fungi in Boletaceae (Boletales, Agaricomycetes, Basidiomycota) and inform their relationships to other known epigeous and sequestrate taxa within that family. Macro- and micromorphological characters, habitat, and multi-locus DNA sequence data are provided for each new taxon. Unique morphological features and a molecular phylogenetic analysis of 185 taxa across the order Boletales justify the recognition of the three new genera.

The ectomycorrhizas of Lactarius cuspidoaurantiacus and Lactarius herrerae associated with Alnus acuminata in Central Mexico

Two pure Alnus acuminata stands established in a montane forest in central Mexico (Puebla State) were monitored between 2010 and 2013 to confirm and recognize the ectomycorrhizal (EcM) systems of A. acuminata with Lactarius cuspidoaurantiacus and Lactarius herrerae, two recently described species. Through comparison of internal transcribed spacer (ITS) of nuclear ribosomal DNA sequences from basidiomes and ectomycorrhizas sampled in the forest stands, we confirmed their ectomycorrhizal association. The phytobiont was corroborated by comparing ITS sequences obtained from EcM root tips and leaves collected in the study site and from other sequences of A. acuminata available in Genbank. Detailed morphological and anatomical descriptions of the ectomycorrhizal systems are presented and complemented with photographs.

Lack of host specificity leads to independent assortment of dipterocarps and ectomycorrhizal fungi across a soil fertility gradient

Plants interact with a diversity of microorganisms, and there is often concordance in their community structures. Because most community-level studies are observational, it is unclear if such concordance arises because of host specificity, in which microorganisms or plants limit each other's occurrence. Using a reciprocal transplant experiment, we tested the hypothesis that host specificity between trees and ectomycorrhizal fungi determines patterns of tree and fungal soil specialisation. Seedlings of 13 dipterocarp species with contrasting soil specialisations were seeded into plots crossing soil type and canopy openness. Ectomycorrhizal colonists were identified by DNA sequencing. After 2.5 years, we found no evidence of host specificity. Rather, soil environment was the primary determinant of ectomycorrhizal diversity and composition on seedlings. Despite their close symbiosis, our results show that ectomycorrhizal fungi and tree communities in this Bornean rain forest assemble independently of host-specific interactions, raising questions about how mutualism shapes the realised niche.