Many were named, but few are current: The Hebeloma of Hesler, Smith, and coauthors.

During the 1970s and 1980s, L. R. Hesler and A. H. Smith, alone, together, or Smith with other authors such as V. S. Evenson and D. H. Mitchel, described numerous North American taxa in Hebeloma. With the inclusion of an early work by Smith and a later work by E. Grilli, who described a species based on material from Smith, 130 taxa were described and form the subject of this paper. Apart from two taxa that were (deliberately) invalidly published and two that were illegitimately published, all others are valid and legitimate names. After study of morphology, habitat, and location of collection (based on available material and information) as well as molecular analysis (insofar as this was successful), of these 128 validly published taxa we regard 14 as being current names; the remaining 114 are synonymized with other current names. These 14 species are Hebeloma albomarginatum, H. alpinicola, H. angelesiense, H. caulocystidiosum, H. immutabile, H. incarnatulum, H. kelloggense, H. mackinawense, H. nitidum, H. olympianum, H. parcivelum, H. praeolidum, H. pungens, and H. sporadicum. This brings up the number of currently recognized, validly published, Hebeloma species in America to 72.

Does One Size Fit All? Variations in the DNA Barcode Gaps of Macrofungal Genera.

The nuclear ribosomal internal transcribed spacer (nrITS) region has been widely used in fungal diversity studies. Environmental metabarcoding has increased the importance of the fungal DNA barcode in documenting fungal diversity and distribution. The DNA barcode gap is seen as the difference between intra- and inter-specific pairwise distances in a DNA barcode. The current understanding of the barcode gap in macrofungi is limited, inhibiting the development of best practices in applying the nrITS region toward research on fungal diversity. This study examined the barcode gap using 5146 sequences representing 717 species of macrofungi from eleven genera, eight orders and two phyla in datasets assembled by taxonomic experts. Intra- and inter-specific pairwise distances were measured from sequence and phylogenetic data. The results demonstrate that barcode gaps are influenced by differences in intra- and inter-specific variance in pairwise distances. In terms of DNA barcode behavior, variance is greater in the ITS1 than ITS2, and variance is greater in both relative to the combined nrITS region. Due to the difference in variance, the barcode gaps in the ITS2 region are greater than in the ITS1. Additionally, the taxonomic approach of "splitting" taxa into numerous taxonomic units produces greater barcode gaps when compared to "lumping". The results show variability in the barcode gaps between fungal taxa, demonstrating a need to understand the accuracy of DNA barcoding in quantifying species richness. For taxonomic studies, variability in nrITS sequence data supports the application of multiple molecular markers to corroborate the taxonomic and systematic delineation of species.

Old but not obsolete: A new life for some of Murrill's (Hebeloma) names.

William Alphonso Murrill was an American mycologist of the early 20th century. He described 1453 new species of Agaricales, Boletales, and Polyporales. Within these were 44 taxa that he described as Hebeloma or that he recombined into Hebeloma. Additionally, there are five species, of which we are aware, that Murrill described within other genera that should be referred to the genus Hebeloma. A further three species described from northern America by J. P. F. C. Montagne, and transferred to Hebeloma by Saccardo, were commented on by Murrill and not accepted within the genus. These 52 taxa are analyzed here, both morphologically and molecularly, as far as possible. For 18 of his types, internal transcribed spacer (ITS) sequences were generated. For two species (H. harperi and H. subfastibile), which were mixed collections, lectotypes are designated. Twenty-three of the taxa analyzed are Hebeloma, as the genus is recognized today, and six of these (H. australe, H. harperi, H. paludicola, H. subaustrale, H. subfastibile, and H. viscidissimum) are regarded as current, i.e., they are names that should be accepted and used. Hebeloma paludicola is an earlier name for H. hygrophilum, described from Europe. Gymnopilus viscidissimus is synonymous with H. amarellum but has priority and is here recombined into Hebeloma. The remaining 17 Hebeloma taxa are synonymized with other species that have priority. The remaining 29 species belong to a range of genera; molecularly supported were Agrocybe, Cortinarius, Inocybe, Inosperma, Phlegmacium, Pholiota, Pseudosperma, and Pyrrhulomyces. Recombinations and synonymizations are made as appropriate and necessary. The names H. alachuanum and H. vatricosum, respectively Inocybe vatricosa, are considered doubtful and should be avoided.

Demystifying Hebeloma: introducing hebeloma.org and its database.

We here announce the launch of the website https://hebeloma.org .

Species determination using AI machine-learning algorithms: Hebeloma as a case study.

The genus Hebeloma is renowned as difficult when it comes to species determination. Historically, many dichotomous keys have been published and used with varying success rate. Over the last 20 years the authors have built a database of Hebeloma collections containing not only metadata but also parametrized morphological descriptions, where for about a third of the cases micromorphological characters have been analysed and are included, as well as DNA sequences for almost every collection. The database now has about 9000 collections including nearly every type collection worldwide and represents over 120 different taxa. Almost every collection has been analysed and identified to species using a combination of the available molecular and morphological data in addition to locality and habitat information. Based on these data an Artificial Intelligence (AI) machine-learning species identifier has been developed that takes as input locality data and a small number of the morphological parameters. Using a random test set of more than 600 collections from the database, not utilized within the set of collections used to train the identifier, the species identifier was able to identify 77% correctly with its highest probabilistic match, 96% within its three most likely determinations and over 99% of collections within its five most likely determinations.

96 North American taxa sorted - Peck's Hebeloma revisited.

Charles Horton Peck described some 2700 species of North American fungi in the 19th and early 20th centuries. Among these were 31 species that he described as Hebeloma or that later authors recombined into Hebeloma. These 31 taxa have been analyzed morphologically and molecularly, as far as possible. For six of these species, lectotypes are designated. For twelve species, ITS sequences (some partial) were generated. Thirteen of the species analyzed are Hebeloma, as the genus is delimited today. Of these 13, nine are regarded as 'current', i.e. are names that should be accepted and used. Of the remaining four, three are synonymized with earlier Peck species and one with the generic type H. mesophaeum. Numerous Hebeloma species described from America are synonymized with some of Peck's species, such as H. albidulum, H. album, H. colvinii, H. excedens, H. palustre, H. sordidulum, and H. velatum; Peck's H. album, H. palustre, and H. velatum are earlier names for H. fragilipes, H. clavulipes, and H. dunense, respectively. All three names were in current use and described from Europe. The 18 species that are not Hebeloma belong to a range of genera: Agrocybe, Hemistropharia, Inocybe, Inosperma, Naucoria, and Pholiota; three species that were not previously recombined into their respective genera are here recombined and one species, Hebeloma commune is synonymized with Pholiota lenta. Two taxa, that are not Hebeloma, remain unresolved. Sixty later Hebeloma taxa described from North America are revised and synonymized with Peck species and seven with H. mesophaeum, 36 of these supported by ITS (some partial) sequence data. Updates on two species, H. petrakii and H. remyi, from Europe, are also given, and a lectotype and epitype selected for the latter.

Not (only) poison pies - Hebeloma (Agaricales, Hymenogastraceae) in Mexico.

The species of Hebeloma have been little studied in Mexico, but have received attention as edibles and in trials to enhance production of edible fungi and tree growth through inoculation of seedlings with ectomycorrhizal fungi. Here we describe three new species of Hebeloma that are currently known only from Mexico. These species belong to separate sections of the genus: H.ambustiterranum is a member of H.sect.Hebeloma, H.cohaerens belongs to H.sect.Theobromina, while H.magnicystidiatum belongs to H.sect.Denudata. All three species were collected from subtropical pine-oak woodland; all records of H.cohaerens came from altitudes above 2500 m. Hebelomaambustiterranum is commonly sold in the local markets of Tlaxcala as a prized edible mushroom. An additional nine species are reported from Mexico, of which eight are new records for the country: H.aanenii, H.eburneum, H.excedens, H.ingratum, H.neurophyllum, H.sordidulum, H.subaustrale and H.velutipes. First modern descriptions of H.neurophyllum and H.subaustrale, originally described from the USA, are given here.

A survey of Hebeloma (Hymenogastraceae) in Greenland.

This is the first study exclusively dedicated to the study of Hebeloma in Greenland. It is based on almost 400 collections, the great majority of which were collected by three of the co-authors over a period of 40 years and were lodged in the fungarium of the Natural History Museum in Copenhagen. The material was identified using molecular and morphological methods. In total, 28 species were recognized, 27 belonging to three sections, H. sects Hebeloma, Denudata and Velutipes. One species sampled was new to science and is here described as H. arcticum. For all species, a description, a distribution map within Greenland and macro and microphotographs are presented. A key is provided for the 28 species. The distribution of species within Greenland is discussed. The findings are placed in the context of studies of arctic and alpine Hebeloma from other parts of the world where comparable data exist. Notably, H. grandisporum, H. louiseae and H. islandicum, previously only known from Romania, Svalbard, Iceland or Norway, respectively, have been found in Greenland. The latter is also the only species encountered that does not belong to any of the above sections. Hebeloma excedens and H. colvinii - for the latter we here publish the first modern description - are to date only known from continental North America and now Greenland.

Hebeloma in the Malay Peninsula: Masquerading within Psathyrella.

In 1994 Corner published five new species within the genus Psathyrella, all having been collected on the Malay Peninsula between 1929 and 1930. Three of these species belong to the genus Hebeloma and with their vinaceous colored lamellae and spore print, when fresh, they belong to H. sect. Porphyrospora. Of these three species, only one, P. flavidifolia, was validly published and thus we herewith recombine it as H. flavidifolium. The other two species, P. splendens and P. verrucispora, are synonyms of H. parvisporum and H. lactariolens, respectively. We also describe a new Malayan species, H. radicans, which also belongs to H. sect. Porphyrospora. These findings confirm the western Pacific Rim as a diversity hotspot for H. sect. Porphyrospora. The records described within this paper, represent the first recognition that the genus Hebeloma, and indeed that members of the ectomycorrhizal Hymenogastraceae, are present on the Malay Peninsula.

Adventurous cuisine in Laos: Hebeloma parvisporum, a new species in Hebeloma section Porphyrospora.

Hebeloma parvisporum is described as new and placed within H. sect. Porphyrospora. This mushroom is sold as an edible in markets of Laos under the local name "wai khom." Hebeloma sect. Porphyrospora is discussed and expanded to include the species formerly included in the genus Anamika and recently transferred to Hebeloma. Hebeloma sect. Porphyrospora currently comprises 16 species, 14 of which are known only from the western Pacific and Indian subcontinent. All species in this section share the character of having red-brown spores when fresh, atypical for other sections of Hebeloma, which causes the lamellae to be red-brown. However, this red-brown color fades when the material is dried. The close links, morphologically and molecularly, between H. parvisporum and other members of H. sect. Porphyrospora, particularly H. victoriense, are shown.

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.

Considerations and consequences of allowing DNA sequence data as types of fungal taxa.

Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.

The taxonomy of the European species of Hebeloma section Denudata subsections Hiemalia, Echinospora subsect. nov. and Clepsydroida subsect. nov. and five new species.

Hebeloma section Denudata includes the majority of the taxa commonly referred to as the Hebeloma crustuliniforme complex. In a recent paper we described in detail H. subsection Denudata and fifteen European species recognised within this subsection, using morphological and molecular methods. In this paper we continue this work and describe in detail three additional subsections and several new species. Within H. subsection Hiemalia we recognise just one species, Hebeloma hiemale. Here we propose an epitype in order to unambiguously define this taxon. Nine species occurring in Europe are assigned to H. subsect. Clepsydroida, namely Hebeloma ammophilum, H. cavipes, H. fragilipes, H. ingratum, H. laetitiae, H. limbatum sp. nov., H. matritense sp. nov., H. pseudofragilipes sp. nov., and H. vaccinum. Finally, we introduce H. subsection Echinospora with three species: Hebeloma echinosporum sp. nov., H. populinum, and H. rostratum sp. nov. We provide descriptions of all three of these species in order to clarify the taxonomy of this section. We provide a key to H. sect. Denudata and the discussed subsections. For the majority of the taxa there is good overall consistency between morphological and phylogenetic delimitation and, where the information exists, thanks to Aanen and Kuyper's work, biological delimitation.

The genus Hebeloma in the alpine belt of the Carpathians including two new species.

Between 2002 and 2012 regular visits to the Carpathians were made and a number of Hebeloma spp. were collected from the alpine area. In total 44 collections were made that represent 11 species, two of which, Hebeloma grandisporum and H. oreophilum, are described here as new. Of the 11 species, four (H. alpinum, H. marginatulum and the two species described as new) are known only from alpine or Arctic habitats. Hebeloma dunense and H. mesophaeum are commonly found in, but not restricted to, alpine habitats. The other five species (H. aanenii, H. laterinum, H. naviculosporum, H. vaccinum, H. velutipes) are usually found in lowland or boreal habitats. Hebeloma naviculosporum is reported for the first time from the alpine zone and H. alpinum for the first time as growing with Helianthemum. All but two species (H. alpinum, H. marginatulum) are reported for the first time from the Carpathian alpine zone. In this paper we discuss the habitat, the 11 recorded species and give detailed descriptions of the two new species, both morphologically and molecularly. A key for Hebeloma species from sect. Hebeloma occurring in Arctic-alpine habitats is provided.

Hebeloma species associated with Cistus.

The genus Hebeloma has a number of species highly specific to Cistus and others that occur with several host genera. This paper discusses the species of Hebeloma that appear to be ectomycorrhizal with Cistus, judging from their occurrence when Cistus is the only available host. The previously unknown species H. plesiocistum spec. nov. is described. We also provide a key to the known Hebeloma associates of Cistus. Molecular analyses based on ITS sequence data further illustrate the distinctness of the newly described species and difficulties in the species delimitation with view to H. erumpens. Specific associations with Cistus may have evolved more than once within the genus Hebeloma.