Hebeloma mesophaeum (Photo: J. Vesterholt)

Taxonomy

• arrow_drop_downarrow_drop_upNomenclatural notes
  A proposal to conserve the generic name Hebeloma with H. mesophaeum as type species by Beker et al. (2013a) was approved by the Nomenclature Committee for Fungi (May, 2015) and ratified by the General Committee (Wilson, 2017). The neotype was originally designated by Singer (Persoonia 2: 33, 1961) but there are no indications as to the date of collection (or even location) and therefore it is not certain that it represents original material studied before the publication of the name. However Singer’s designation can be considered a neotypification under Art. 9.9. This material is in accordance with the protologue and as there are no other candidate original materials and no cited illustrations we accept this as a neotype.

Basionym:
Agaricus fastibilis var. mesophaeus Pers., Mycologia Europaea: 173 (1828)

Types: DENMARK: NEJ, Kirkemilen,Skagen Klitplantage UTM NJ 91,97 TBU 01 (approx. 57.71°N, 10.55°E, alt. approx. 5 m a.s.l.) on sandy soil in coniferous woodland plantation under Pinus sylvestris and Salix repens, 26 Sep. 2003, A. Eriksen, J. Vesterholt (JV-03-547), det: J. Vesterholt (Epitype. herbarium acc. no. C JV-03-547, HJB10854). Epitype designated by Beker et al., Taxon 62 (5): (2013) page 1059. FRANCE: in woodland under Pinus sp. and Quercus sp., , C.H. Persoon (Neotype. herbarium acc. no. L910.255-852, L L0115239, HJB1000296). Neotype designated by Singer, Persoonia 2 (1): (1961) page 33.

• arrow_drop_downarrow_drop_upType notes
  The neotype was designated as a “lectotype” by Singer (Persoonia 2: 33, 1961) but there are no indications as to the date of collection (or even location) and therefore it is not certain that it represents original material studied before the publication of the name. However Singer’s designation can be considered a neotypification under Art. 9.9. This material is in accordance with the protologue and as there are no other candidate original materials and no cited illustrations we accept this as a neotype.

Heterotypic synonyms:

• Hebeloma bruchetii Bon, Bulletin trimestriel de la Fédération Mycologique Dauphiné-Savoie 102: 23 (1986)
• Hebeloma caespitosum Velen., Ceske Houby: 389 (1919) ["1920"]
• Hebeloma cinereum Velen., Ceske Houby: 396 (1919) ["1920"]
• Hebeloma mammillatum Velen., Nov. Mycol. L. Soucek, Prague: 118 (1939)
• Hebeloma mesophaeum f. cremeovelatum Bon & Haluwyn, Documents mycologiques 13 (50): 37 (1983)
• Hebeloma mesophaeum var. crassipes Vesterh., Nord. J. Bot. 9 (3): 298 (1989)
• Hebeloma mesophaeum var. cremeovelatum Bon & Quadr., Documents mycologiques 14 (56): 31 (1985) ["1984"]
• Hebeloma mesophaeum var. minus (Cooke) Massee, British Fungus-Flora. A Classified Text-Book of Mycology 2: 176 (1893)
• Hebeloma mesophaeum var. ochroniveum Quadr., Documents mycologiques 14 (56): 31 (1985) ["1984"]
• Hebeloma mesophaeum var. strophosum (Fr.) Quadr., Documents mycologiques 14 (56): 31 (1985) ["1984"]
• Hebeloma petrakii Hruby ex. Singer, The Agaricales in Modern Taxonomy 22: 538 (1951) ["1949"]
• Hebeloma repandum Bruchet, Bull. Mens. Soc. Linn. Lyon 39, supplement 6: 126 (1970)
• Hebeloma strophosum (Fr.) Sacc., Syll. Fung. 5: 808 (1887)
• Hebeloma subcollariatum (Berk. & Broome) Sacc., Syll. Fung. 5: 798 (1887)
• Inocybe velenovskyi Hruby, Hedwigia 70 (3-4): 281 (1930)
• Inocybe velenovskyi f. incrassata Hruby, Hedwigia 70 (3-4): 281 (1930)
• Hebeloma gregarium Peck, Ann. Rep. N.Y. St. Mus. 49: 32 (1897) ["1896"]
• Hebeloma lateritium Murrill, N. Amer. Fl. 10 (3): 224 (1917)
• Hebeloma maritinum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 99 (1983)
• Hebeloma mesophaeum var. imitatum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 75 (1983)
• Hebeloma mesophaeum var. lateritium (Murrill) A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 72 (1983)
• Hebeloma mesophaeum var. longipes A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 170 (1983)
• Hebeloma mesophaeum var. subobscurum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 74 (1983)
• Hebeloma mesophaeum var. velovinaceum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 73 (1983)
• Hebeloma vinaceogriseum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 28 (1983)
• Hebeloma moseri Singer, Beihefte zur Nova Hedwigia 29: 287 (1969)
• Agaricus mesophaeus var. minor (Cooke) Cooke [as "Agaricus (Hebeloma) var. minor"], Handbook of British Fungi Edn. 2: 163 (1886)
• Agaricus mesophaeus f. minor Cooke [as "Agaricus (Hebeloma) mesophaeus f. minor"], Illustr. Br. Fungi: 412 (1884)
• Agaricus strophosus Fr., Epicrisis Systematis Mycologici seu Synopsis Hymenomycetum: 161 (1838) ["1836-1838"]
• Agaricus subcollariatus Berk. & Broome, Annals and Magazine of Natural History 5th Ser. 9: 178 (1882)
• Roumeguerites strophosus (Fr.) P. Karst., Bidrag Kännedom Finlands Natur Folk 32: 452 (1879)
• Hylophila versipellis var. strophosa (Fr.) Quél., Enchiridion Fungorum in Europa Media et Praesertim in Gallia Vigentium: 99 (1886)
• Hebelomatis repandum Locq., Flore Mycologique Vol III - Text. Cortinariales A: 146 (1979) ["1977"]
• Agaricus victoriae Cooke & Massee [as "Agaricus (Inocybe) victoriae"], Grevillea 16 (79): 72 (1888)
• Inocybe victoriae (Cooke & Massee) Sacc., Syll. Fung. 9.: 101 (1891)
• Hebeloma victoriae (Cooke & Massee) Pegler, Aust. J. Bot. 13: 347 (1965)
• Hebeloma fallax Hruby, Verhandlungen des naturforschenden Vereines in Brünn 66: 91 (1934)
• Hebeloma versipelle var. strophosum (Fr.) Costantin & L.M. Dufour [as "strophosus"], Nouv. Fl. Champ.: 107 (1891)

Homotypic synonyms:

• Agaricus mesophaeus (Pers.) Fr. ["1836-1838"], Epicrisis Systematis Mycologici seu Synopsis Hymenomycetum: 179 (1838) ["1836-1838"]
• Inocybe mesophaea (Pers.) P. Karst., Bidrag Kännedom Finlands Natur Folk 32: 470 (1879)
• Hylophila mesophaea (Pers.) Quél., Enchiridion Fungorum in Europa Media et Praesertim in Gallia Vigentium: 99 (1886)
• Inocybe versipellis var. mesophaea (Pers.) S. Petersen, Danske Agaricaceer: 337 (1911) ["1907-1911"]
• Hebeloma versipelle subsp. mesophaeum (Pers.) Konrad & Maubl., Icones Selectae Fungorum 1: 78 (1929)
• Hebeloma versipelle var. mesophaeum (Pers.) Costantin & L.M. Dufour [as "mesophaeus"], Nouv. Fl. Champ.: 107 (1891)

• arrow_drop_downarrow_drop_upEtymology
  From Greek meso– in the middle, and phaeus– dark-coloured. Persoon particularly mentions the peculiar reddish brown pileus centre “disco rufo-fusco peculiaris” which is characteristic of this taxon.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  Gregarius minor. Pileo subtenui umbonato applanato subviscoso livide rufescente, umbone obscuriore, lamellis adnexis, primo albidis, dein argillaceis aut aquose cinnamomeis, stipite tenui subelongato fibrilloso cortinato. Frequens his in regionibus sub pinubus, in dumetis, passim quoque in quercetis occurrit, sed serior quam antecedens. Sapore fastibili antecedentis est. Pileus fragilis. fere ecarnis. 1.5 unc latus, disco rufo-fusco peculiaris. Lamel. subventricosae, 3 lin. latae. Stipes 2–3 unc. longus, 2–3 lin. crassus, aequalis, albido pallescens. Cortina tenuis, subcinnamoea. Obs. Secundum ill. Sprengel, in Linn. Syst veg. Ed. XVI. p. 460; Ag. vibratilis Fries Syst. 1 p. 26. mera A. fastibilis est var, et Ejusd. A. saginus p.226. non equidem valde distat; sed velo gaudet viscoso, tenui, fugacissimo, caractere equidem haud magni momenti aestumando; in fungo alioquin prateo.

• arrow_drop_downarrow_drop_upEnglish translation
  Gregarious, small. Pileus somewhat thin, umbonate, applanate, subviscid, livid-reddish, with darker umbo; lamellae adnexed, white at first, then pale brown or watery cinnamon-coloured, stipe slender, not very long, fibrillose with cortina. Frequent in pine regions, in copses, and also in Quercus woodlands, but later than the preceding species (H. fastibile). Taste like the former H. fastibile. Pileus fragile, almost without flesh [thin-fleshed], about 4 cm broad, with peculiar reddish brown centre. Lamellae subventricose, 7.5 mm broad. Stipe 5–10 cm long, 5–7.5 mm thick, equal, white, pallescent. Cortina thin, somewhat cinnamon coloured. According to the illustrations observed by Sprengel, in Linn. Syst. Veg. Ed. XVI. p. 460; A. vibratilis Fries Syst. 1 p. 26 is merely a variety of A. fastibilis and equally A. saginus, p. 226 is not very distant, but the veil is pretty viscid, thin, and very fugacious, a character that currently is not considered of great importance; growing in meadows.

Description

Description of Hebeloma mesophaeum based on 477 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (2) 14–44 (70) mm diameter; shape occasionally convex, umbonate or papillate, rarely broadly umbonate, applanate, strongly umbonate or weakly umbonate; characters often remains of universal veil, rarely hygrophanous, spotting, pruinose, rimulose or tomentose; margin characters often smooth, rarely involute, overhanging pileus, eroded, reflexed, scalloped, wavy, crenulate, fibrillose or sulcate; viscosity tacky when moist; colour variation usually two color, occasionally unicolour; colour at centre occasionally umber, sepia, yellowish brown or dark brick, rarely orange-brown, brownish olive, clay-buff, cinnamon, brick, dark pinkish buff, fuscous, ochraceous, clay-red, paler or cream.

  Lamellae: attachment often emarginate, occasionally adnate, rarely adnexed, decurrent tooth or decurrent; maximum depth 2–6 mm; number of complete lamellae 32–56; presence of tears usually absent, rarely visible with naked eye or visible with x10 lens; white fimbriate edge often present, occasionally weak, rarely very strong.

  Cortina presence: yes.

  Stipe: (14) 23–75 (113) x 2–7 (14) {median} x (1) 2–7 (14) {basal} mm; stipe Q 2.8–34.0; base shape usually cylindrical, rarely clavate, tapering, subbulbous, bulbous or sand bulb; floccosity often fibrillose, occasionally pruinose at apex, rarely none, fibrous, floccose, floccose at apex or pruinose; rooting usually no, rarely yes or weak; thick rhizoids at base absent;

  Context: Texture firm; stipe interior often hollow, occasionally stuffed, rarely superior wick; stipe flesh discolouring often yes, rarely no, weak or very strongly; slenderness measure 1.6–87.2; smell often raphanoid, occasionally odourless, rarely weakly raphanoid, strongly raphanoid, cocoa, fruit, soap or tea; taste occasionally raphanoid, weakly raphanoid, mild, bitter or weakly bitter, rarely none where recorded.

  Spore deposit colour: occasionally brownish olive or yellowish brown, rarely umber, cinnamon or clay-buff.

  Exsiccata characters: rarely dark, fragile, lamellae blackening, pale, pileus blackening or shiny.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape ellipsoid, occasionally ovoid, rarely cylindrical or limoniform; colour in microscope occasionally yellow, brown pale or grey yellow, rarely yellow brown, yellow pale or brown; guttules occasionally no, weak or yes. papilla no; Spore Code: O1; P0; D0 (D1).

  Basidia: (18) 20–34 (43) x (4) 5–9 (10) μm; ave. Q 3.1–4.4; spore arrangement 4 spored;

  Cheilocystidia: main shape usually lageniform or ventricose, occasionally cylindrical, rarely clavate or lentiform; special features observed occasionally septa, rarely geniculate, many collapsed in exsiccata, apical thickening, basal thickening, yellow contents, clamped septa, median thickening, thick content in neck, mucous, bifurcate, grotesque, irregular or short; cheilocystidia ratios: A/M = 0.92–1.25; A/B = 0.47–0.85; B/M = 1.36–2.19.

  Pleurocystidia: usually none seen, rarely only close to lamella edge.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 350 μm; ixocutis hyphae width up to 10 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis occasionally thickly sausage-shaped, ellipsoid, isodiametric or polygonal, rarely angular, cylindrical, oblong or thinly sausage-shaped up to 22 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 130 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Where only one possible associate was recorded, the most commonly recorded associate was Salix (23.2%) but Pinus (18.3%), Betula (12.1%), Fagus (8.0%), Picea (7.1%), Populus (5.8%), Eucalyptus (4.9%), Abies (3.6%), Tilia (3.1%), Dryas (3.1%), Cedrus (2.2%), Quercus (1.8%), Larix (1.3%), Nothofagus (1.3%) and Pseudotsuga (1.3%) were also recorded. In these cases the most commonly recorded families were Pinaceae (37.5%), Salicaceae (27.5%), Betulaceae (11.9%) and Fagaceae (9.6%). We have additional records where Alnus (4.2%) and Tsuga (2.4%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Pinaceae (45.5%), Salicaceae (37.1%), Betulaceae (25.8%) and Fagaceae (13.9%) The growth habit of our collections was often scattered and rarely gregarious, solitary or caespitose.

  According to our current data, the species is found on multiple continents with collections found in Europe (67.5%), Northern America (24.5%), Temperate Asia (3.9%), Australasia (3.5%), Southern America (0.4%) and Tropical Asia (0.2%). On these continents, collections have been found in the WWF biomes The World Wildlife Fund (WWF) have divided the world into 867 terrestrial ecoregions. The ecoregion here is estimated by mapping from the GPS coordinates of the collection using data made available by Dinerstein et al (2017). Use this webtool to explore the ecoregions visually or see a full list of current ecoregions on Wikipedia. temperate broadleaf & mixed forests (53.5%) and temperate conifer forests (16.1%). From collector information, it appears collections have been found in the 1.4 Forest – Temperate (44.4%) and 14.5 Urban Areas (11.3%) IUCN habitats We map from the collector's description of the habitat to the International Union for Conservation of Nature (IUCN)'s definition using a standardised set of rules. Please see this page for a full list of IUCN habitats..

  Within Europe we have records from the North (England, Svalbard, Denmark, Iceland, Scotland, Norway, Isle Of Man, Sweden, Faroe Islands and Finland), the Centre (Belgium, Poland, Germany, Switzerland, Czech Republic, Slovakia and Austria), the Southwest (France, Spain, Channel Islands, Andorra and Italy), the Southeast (Italy, North Macedonia and Romania) and Eastern Europe (Estonia). Specimens have been collected from 36.6°N to 79.1°N.

  Within Northern America we have records from Subarctic America (Alaska, Yukon, Northwest Territories, Nunavut and Greenland), Eastern Canada (Quebec, Newfoundland and Labrador, Ontario and Nova Scotia), Northwestern U.S.A. (Colorado, Washington, Oregon and Idaho), Northeastern U.S.A. (Michigan, Pennsylvania, New York and New Jersey), Mexico (Mexico), Southwestern U.S.A. (California, Arizona and Utah), Western Canada (British Columbia and Alberta) and South-central U.S.A. (New Mexico).

  Within Temperate Asia we have records from Caucasus (Karachay-Balkar, Georgia and Adygea), Western Asia (Cyprus and Turkey), Middle Asia (Kazakhstan) and China (Sichuan).

  Within Australasia we have records from New Zealand (New Zealand) and Australia (Victoria and Tasmania).

  Within Southern America all our records are from Southern South America (Argentina and Chile).

  Within Tropical Asia all our records are from Indian Subcontinent (Pakistan).

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma mesophaeum is not monophyletic in any of the molecular results, neither single nor multi-locus. The species is part of a clade also including H. dunense, H. psammophilum, H. pubescens and H. subtortum. In the protein-coding loci RPB2 and Tef1a the majority of the sequences of H. mesophaeum even form a monophyletic subclade, but in both cases the same collection (HJB13109) is not included. Also in the ITS, this collection is in that part of the tree where H. dunense and H. mesophaeum overlap. At this point it is impossible to tell whether this is a significant result or not. Hebeloma mesophaeum is one of the most diverse species in terms of intraspecific ITS variation. Intraspecific variation, in combination with the existence of closely related species, imply that H. mesophaeum cannot (always) be recognized molecularly from the species named in the previous paragraph. It is possible, that there are additional species hidden within H. mesophaeum. It is also possible that the large ecological amplitude and wide distribution have slowed down population genetic processes (genetic drift, fixation of genetic differences etc.), so that species recognition remains problematic within this clade. We recognize many synonyms of H. mesophaeum and we have ITS data for a selection of them (H. bruchetii, H. subcollariatum, H. mesophaeum var. crassipes, H. mesophaeum var. cremeovelatum and H. mesophaeum var. ochroniveum). These and the ITS of the epitype of H. mesophaeum are all in the “tail“ of the clade, where H. mesophaeum is not mixed with other species. While this is hardly a strong result, it supports the synonymization.

• arrow_drop_downarrow_drop_upCommentary
  With the persistent presence of a cortina and the lageniform or ventricose cheilocystidia, this taxon clearly belongs in H. section Hebeloma. Within this section, H. mesophaeum with its primarily indextrinoid or indistinctly dextrinoid ellipsoid spores, very rarely amygdaloid and only occasionally ovoid, and spores at most 10.5 μm long or at most 6.1 μm wide, can only be confused with H. subtortum. But as mentioned above while H. mesophaeum is more common in Northern Europe and less common in Southern Europe, H. subtortum strongly favours Southern Europe. Perhaps more reliably, H. subtortum has more robust basidiomes (stipe width greater than 4 mm), a larger number of lamellae (L at least 50) and most spores ovoid (rather than ellipsoid) and pale yellow under the microscope. The other species with many ellipsoid spores (with the exception of H. subtortum and H. psammophilum) appear to be restricted to Salix, while, as discussed earlier, H. mesophaeum is associated with many different trees and shrubs. In non-arctic and non-alpine areas some confusion may arise with H. dunense, if a collection has larger than usual spores. In this case the more ornamented spores of H. dunense are a clear indicator of this species; H. mesophaeum has spores, which under the light microscope appear almost smooth even at high magnification. In arctic and alpine areas there is more chance of confusion due not only to the presence of H. marginatulum, but also to the fact that sometimes H. mesophaeum, growing in such habitats, tends to have larger spores. Of our 277 database collections of this taxon, all the ‘large-spored’ collections appear to be from Iceland and Svalbard. If we consider only the Svalbard collections, the spore averages are 10.1–12.1 × 6.3 – 6.8, i.e. they are all ‘large-spored’. (The Icelandic collections include ‘large-spored’ collections and ‘normal’ collections.) We did consider creating a variety of H. mesophaeum to address these collections, but have decided against this course of action for the time being. We believe further work needs to be done to understand what is happening and, in particular, comparison needs to be made with arctic (and alpine) collections from outside Europe. In our key these ‘large-spored H. mesophaeum’ collections will key out to H. marginatulum and may be difficult to differentiate from that taxon. The strongly two-coloured pileus of H. mesophaeum will help separate these taxa, particularly since, as far as we are aware, it is only collections from these two regions where this confusion may arise. We do have a number of collections of H. mesophaeum from outside Europe. In particular, we have collections from New Zealand and North America that correspond perfectly with our taxon here. In the case of New Zealand, we suspect that this Hebeloma sp. arrived there with tree seedlings. The same may be true for North America. However, H. mesophaeum, with its capacity to grow in arctic and alpine environments, is likely also to have been present before. Interestingly, we also have many collections from North America of a taxon that appears, morphologically, very close to H. mesophaeum, and is also very close to H. mesophaeum from a molecular viewpoint, but does have consistent and clear (albeit small) molecular differences. At this time we are not certain what name to apply to these North American collections. Intriguingly, we have no collections of this taxon from Europe. We hope to address these issues as part of our ongoing exploration of the North American Hebeloma. The name Hebeloma mesophaeum has been applied consistently to this mushroom, common in Northern Europe and distinguished from other Hebeloma species by the presence of a cortina and fairly small, pale and weakly ornamented, ellipsoid spores, its typically buff to greyish-brown pileus with a more intensely brown centre, hence the species epithet. The name has been used in this sense in the monographic treatments of Bruchet (1970), Vesterholt (1989, 2005), Lange (1938a), Kühner & Romagnesi (1953), Moser (1970) and a large number of popular books. As such we believe it to be a good candidate to replace H. fastibile, a name which has never been applied consistently to any taxon, as type of the genus. A proposal to conserve the name Hebeloma in this way was made, Beker et al (2013a) and has been accepted by the Nomenclature Committee (2015) and now awaits ratification from the General Committee. There are two collections of H. mesophaeum in Persoon’s herbarium at Leiden. Singer (1961) selected collection 910.255-852 as lectotype. There are no indications as to the date of collection and, therefore, it is not certain that it represents original material. However, as mentioned earlier we accept this collection as neotype. It is in remarkably good condition. As a result we were able to construct a reasonably comprehensive description for this collection, to complement the description of the epitype. Both these collections are included in our composite description of this species. Hebeloma mesophaeum has many synonyms. We suspect that it has many more than those we have listed here, but although in many cases we suspect the synonymy, where no material exists, we cannot totally rule out other possibilities. One does not normally associate this species with pleurocystidia, and when carrying out an analysis it is rare to look for pleurocystidia in European species of this taxon, but we should mention that we do, albeit rarely, find a few sparse pleurocystidia.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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