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The family Tricholomataceae, contained within the Tricholomatoid clade, has traditionally been one of the largest families of the Agaricales. However, in this sense it is highly polyphyletic and requires emendation. Here, we present a phylogeny of the Tricholomatoid clade based on nucleotide sequence data from two nuclear ribosomal RNA genes (large subunit and small subunit) and the second‐largest subunit of RNA polymerase II (rpb2). Our aim is to delimit the Tricholomataceae and identify monophyletic groups within the Tricholomatoid clade. We also infer a separate phylogeny, based on the three genes above, in addition to sequences of the nuclear ribosomal internal transcribed spacers (ITS), in order to evaluate generic‐level boundaries within the Tricholomataceae s.str. Based on this analysis we recover seven monophyletic genera within the Tricholomataceae s.str. that correspond to Leucopaxillus, Tricholoma, Pseudotricholoma stat. nov., Porpolomas.str., Dennisiomyces, Corneriella gen. nov., and Albomagister gen. nov. Of the 98 genera that have been traditionally assigned to the Tricholomataceae sensu Singer, only four can be placed within it (Tricholoma, Porpoloma, Dennisiomyces, Leucopaxillus). The genus Porpoloma is highly polyphyletic and divided into four genera: Porpoloma s.str., Corneriella gen. nov., Pseudotricholoma stat. nov., and Pogonoloma stat. nov. In all, four new genera are proposed. Taxonomic descriptions, and a key to genera of the Tricholomat‐ aceae as emended here are also presented.

Rhizomorpha corynecarpos Kunze was originally described from wet forests in Suriname. This unusual fungus forms white, sterile rhizomorphs bearing abundant club-shaped branches. Its evolutionary origins are unknown because reproductive structures have never been found. Recent collections and observations of R. corynecarpos were made from Belize, Brazil, Ecuador, Guyana, and Peru. Phylogenetic analyses of three nuclear rDNA regions (internal transcribed spacer, large ribosomal subunit, and small ribosomal subunit) were conducted to resolve the phylogenetic relationship of R. corynecarpos. Results show that this fungus is sister to Brunneocorticium bisporum—a widely distributed, tropical crust fungus. These two taxa along with Neocampanella blastanos form a clade within the primarily mushroom-forming Marasmiaceae. Based on phylogenetic evidence and micromorphological similarities, we propose the new combination, Brunneocorticium corynecarpon, to accommodate this species. Brunneocorticium corynecarpon is a pathogen, infecting the crowns of trees and shrubs in the Neotropics; the long, dangling rhizomorphs with lateral prongs probably colonize neighboring trees. Longer-distance dispersal can be accomplished by birds as it is used as construction material in nests of various avian species.

Fungal interactions during leaf decomposition can facilitate or inhibit other fungi. This experiment focused on whether preconditioning of leaf litter by microfungi that were confined to one leaf (Unit-Restricted) made leaf litter less likely to be colonized and decomposed by basidiomycetes that bind litter into mats (Non-Unit-Restricted) than non-preconditioned litter. Leaves of Manilkara bidentata in litterbags were preconditioned by incubating them for 0, 1, 2 or 3 months in flat litter/seed rain baskets 10 cm above the forest floor to avoid colonization by basidiomycete fungi. Preconditioned and non-preconditioned leaves were transferred to 5 replicate basidiomycete fungal mats of Gymnopus johnstonii for 6 weeks. Both attachment by basidiomycete fungi and percent mass loss after 6 weeks decreased significantly with increasing preconditioning time. In non-preconditioned leaves, gamma irradiation did not affect mass loss or percent white-rot despite having significantly increased numbers of basidiomycete fungal connections as compared to non-irradiated leaves. In non-preconditioned leaves, more basidiomycetes attachmented to non-irradiated than irradiated leaves suggest facilitation by phyllosphere microfungi. While basidiomycete colonization was initially facilitated by phyllosphere fungi, we inferred that degradation of resource quality led to fewer fungal attachments and less mass loss after 1–3 months of preconditioning by microfungi. The date suggest there is a 1-month time window for basidiomycete fungi to incorporate fallen leaves into their litter mats.

Morphological and molecular phylogenetic studies of true morels (Morchella) in North America, the Dominican Republic, Venezuela, Ecuador, and Peru led to the discovery of four undescribed species of Morchella. Two new species in the Elata clade, one from the Dominican Republic, initially distinguished by the informal designation Mel-18, and a newly discovered sister species from northern Arizona, are now recognized. Mel-18 is described as a novel phylogenetically distinct species, M. hispaniolensis. Its sister species from Arizona is described as M. kaibabensis, also recovered as an endophyte of Rocky Mountain juniper. Two additional species in the Esculenta clade, M. peruviana discovered in Peru and M. gracilis (previously reported as Mes-14) from the Dominican Republic, Venezuela, and Ecuador, are described as new. We also demonstrate that scanning electron microscopy (SEM) imaging of ascospores using rehydration/dehydration/critical point drying preparation techniques provides for enhanced resolution of spore wall surfaces, thereby increasing the number of morphological traits available to assess differences among otherwise closely related species.

The ectomycorrhizal (ECM) mushroom family Inocybaceae is widespread in north temperate regions, but more than 150 species are encountered in the tropics and the Southern Hemisphere. The relative roles of recent and ancient biogeographical processes, relationships with plant hosts, and the timing of divergences that have shaped the current geographic distribution of the family are investigated. Africa, Australia, Neotropics, New Zealand, north temperate zone, Palaeotropics, Southeast Asia, South America, south temperate zone. We reconstruct a phylogeny of the Inocybaceae with a geological timeline using a relaxed molecular clock. Divergence dates of lineages are estimated statistically to test vicariance-based hypotheses concerning relatedness of disjunct ECM taxa. A series of internal maximum time constraints is used to evaluate two different calibrations. Ancestral state reconstruction is used to infer ancestral areas and ancestral plant partners of the family. The Palaeotropics are unique in containing representatives of all major clades of Inocybaceae. Six of the seven major clades diversified initially during the Cretaceous, with subsequent radiations probably during the early Palaeogene. Vicariance patterns cannot be rejected that involve area relationships for Africa-Australia, Africa-India and southern South America-Australia. Northern and southern South America, Australia and New Zealand are primarily the recipients of immigrant taxa during the Palaeogene or later. Angiosperms were the earliest hosts of Inocybaceae. Transitions to conifers probably occurred no earlier than 65 Ma. The Inocybaceae initially diversified no later than the Cretaceous in Palaeotropical settings, in association with angiosperms. Diversification within major clades of the family accelerated during the Palaeogene in north and south temperate regions, whereas several relictual lineages persisted in the tropics. Both vicariance and dispersal patterns are detected. Species from Neotropical and south temperate regions are largely derived from immigrant ancestors from north temperate or Palaeotropical regions. Transitions to conifer hosts occurred later, probably during the Palaeogene.

Fungi that bind leaf litter into mats and produce white‐rot via degradation of lignin and other aromatic compounds influence forest nutrient cycling and soil fertility. Extent of white‐rot litter mats formed by basidiomycete fungi in Puerto Rico decreased in response to disturbances—a simulated hurricane treatment executed by canopy trimming and debris addition in 2014, a drought in 2015, a treefall, and two hurricanes 10 days apart in September 2017. Percent fungal litter mat cover ranged from 0.4% after Hurricanes Irma and Maria to a high of 53% in forest with undisturbed canopy prior to the 2017 hurricanes, with means mostly between 10% and 45% of fungal litter mat cover in undisturbed forest. Drought decreased litter mat cover in both treatments, except in one control plot dominated by a drought‐resistant fungus, Marasmius crinis‐equi. Percent fungal litter mat cover sharply declined after hurricanes, a treefall, and a simulated hurricane treatment. Solar radiation was significantly inversely correlated with relative humidity (RH) and percent litter mat cover within each of the four climatic seasons. Solar radiation was also directly correlated with prior month litterfall, while RH was moderately correlated with throughfall, rain, and litter wetness. However, rainfall was inversely correlated with litter mat cover, possibly due to erosion or saturation during high rainfall events. Canopy opening reduced leaf fall and litter mat cover but these variables were not correlated except in winter. The main factor inhibiting basidiomycete fungi that bind leaf litter into mats was likely lower litter moisture associated with drought and increased solar radiation from canopy opening but secondary compounds in green litterfall may have contributed. Although higher litterfall likely increases fungal mat cover under closed canopy, changes in environmental factors apparently had a stronger inhibitory effect following canopy disturbances. Drought tolerance of some basidiomycete fungal litter mat species provided some resilience to drought.

Hurricanes alter forest habitat by opening the canopy and depositing fresh wood and leaves. The objectives of this study were to evaluate the effects of hurricane and drought‐driven changes to forests on green litter decomposition, invertebrate communities, and nutrient mineralization over a short period (6 months) after disturbance. We used three complete replicated blocks with two canopy treatments: control and trim + detritus. Green leaves were enclosed in litterbags of three different mesh sizes to determine the effect of soil fauna of varying body sizes. Litterbags were retrieved from the field after 21, 35, 84, and 168 days and transported to the laboratory in individually sealed plastic bags. We extracted and identified invertebrates, measured leached and mineralized litter nutrients using ion resin membranes placed for 1 week under the leaves inside the litterbags, and determined litter mass loss. Additional resin membranes were placed in the lowest litter layer above the mineral soil. The number of arthropod taxonomic groups and nutrient mineralization differed significantly between control and trim + detritus. Regardless of mesh size, bags in control plots had consistently higher invertebrate richness than in trim + detritus plots. Nitrogen mineralization and phosphorous mineralization were significantly higher in trim + detritus in large mesh size, and decomposer arthropod abundance was highest in large‐sized mesh bags. These data suggest that within functional categories, variations in feeding behavior among arthropod orders may affect the release of nutrients from organic matter. Percent mass loss did not differ between canopy treatments or litterbag mesh sizes, but instead decreased during drought. Invertebrate composition, but not abundance, differed significantly between canopy treatments with greater dominance by shredders (Lepidoptera and Diptera larvae) in trim + detritus, which corresponded to higher rates of nutrient mineralization from green leaves. These results suggest that regional drought dominated the mesoclimate surpassing any microclimate variation in response to canopy treatments. Since mass loss did not differ between canopy treatments or litterbag mesh sizes, our results suggest that differences in short‐term nutrient fluxes from green litter are mostly related to changes in the litter invertebrate food web rather than rates of decomposition.

Agaric fungi of the southern Appalachian Mountains including Great Smoky Mountains National Park are often heterozygous for the rDNA internal transcribed spacer region (ITS) with >42% of collections showing some heterozygosity for indels and/or base-pair substitutions. For these collections, intra-individual haplotype divergence is typically less than 2%, but for 3% of these collections intra-individual haplotype divergence exceeds that figure. We hypothesize that high intra-individual haplotype divergence is due to hybridization between agaric fungi with divergent haplotypes, possibly migrants from geographically isolated glacial refugia. Four species with relatively high haplotype divergence were examined: Armillaria mellea, Amanita citrina f. lavendula, Gymnopus dichrous and the Hygrocybe flavescens/chlorophana complex. The ITS region was sequenced, haplotypes of heterozygotes were resolved through cloning, and phylogenetic analyses were used to determine the outcome of hybridization events. Within Armillaria mellea and Amanita citrina f. lavendula, we found evidence of interbreeding and recombination. Within G. dichrous and H. flavescens/chlorophana, hybrids were identified but there was no evidence for F 2 or higher progeny in natural populations suggesting that the hybrid fruitbodies might be an evolutionary dead end and that the genetically divergent Mendelian populations from which they were derived are, in fact, different species. The association between ITS haplotype divergence of less than 5% (Armillaria mellea = 2.6% excluding gaps; Amanita citrina f. lavendula = 3.3%) with the presence of putative recombinants and greater than 5% (Gymnopus dichrous = 5.7%; Hygrocybe flavescens/chlorophana = 14.1%) with apparent failure of F 1 hybrids to produce F 2 or higher progeny in populations may suggest a correlation between genetic distance and reproductive isolation.

Data on macrofungal diversity and distribution patterns were compiled for major geographical regions of the world. Macrofungi are defined here to include ascomycetes and basidiomycetes with large, easily observed spore-bearing structures that form above or below ground. Each coauthor either provided data on a particular taxonomic group of macrofungi or information on the macrofungi of a specific geographic area. We then employed a meta-analysis to investigate species overlaps between areas, levels of endemism, centers of diversity, and estimated percent of species known for each taxonomic group for each geographic area and for the combined macrofungal data set. Thus, the study provides both a meta-analysis of current data and a gap assessment to help identify research needs. In all, 21,679 names of macrofungi were compiled. The percentage of unique names for each region ranged from 37% for temperate Asia to 72% for Australasia. Approximately 35,000 macrofungal species were estimated to be “unknown” by the contributing authors. This would give an estimated total of 56,679 macrofungi. Our compiled species list does not include data from most of S.E. Europe, Africa, western Asia, or tropical eastern Asia. Even so, combining our list of names with the estimates from contributing authors is in line with our calculated estimate of between 53,000 and 110,000 macrofungal species derived using plant/macrofungal species ratio data. The estimates developed in this study are consistent with a hypothesis of high overall fungal species diversity.

Fungi play major roles in ecosystem processes, but the determinants of fungal diversity and biogeographic patterns remain poorly understood. Using DNA metabarcoding data from hundreds of globally distributed soil samples, we demonstrate that fungal richness is decoupled from plant diversity. The plant-to-fungus richness ratio declines exponentially toward the poles. Climatic factors, followed by edaphic and spatial variables, constitute the best predictors of fungal richness and community composition at the global scale. Fungi show similar latitudinal diversity gradients to other organisms, with several notable exceptions. These findings advance our understanding of global fungal diversity patterns and permit integration of fungi into a general macroecological framework. Global metagenomics detects hotspots of fungal diversity and macroecological patterns and indicates that plant and fungal diversity are uncoupled. [Also see Perspective by Wardle and Lindahl ] Fungi are hyperdiverse but poorly known, despite their ecological and economic impacts. Tedersoo et al. collected nearly 15,000 topsoil samples from 365 sites worldwide and sequenced their genomes (see the Perspective by Wardle and Lindahl). Overall, they found a striking decline in fungal species richness with distance from the equator. For some specialist groups though, diversity depended more on the abundance of host plants than host diversity or geography. The findings reveal a huge gap between known and described species and the actual numbers of distinct fungi in the world's soils. Science , this issue 10.1126/science.1256688 ; see also p. 1052