Hebeloma nauseosum (Photo: J. Vesterholt)

Taxonomy

• arrow_drop_downarrow_drop_upNomenclatural notes
  This is a replacement name for Agaricus nauseosus Cooke (1887),Nom. illegit., non Agaricus nauseosus Pers. Syn Meth, Fung. 2: 446 (1801).

Types: Cooke, Illustr. Br. Fungi: 102 (1888) pl. 963, lectotype (icon) designated by Beker et al., Hebeloma (Fr.) P. Kumm.: (2016) page 519 (MBT203469) ITALY: Marches, Carpegna7 (43.7718°N, 12.3402°E, alt. approx. 730 m a.s.l.) on bare soil in deciduous woodland under Quercus sp., 16 Oct. 2004, H.J. Beker (Epitype. herbarium acc. no. BR 5020184122478, HJB10345). Epitype designated by Beker et al., Hebeloma (Fr.) P. Kumm.: (2016) page 519 (MBT203470).

• arrow_drop_downarrow_drop_upType notes
  The plate (icon) designated as lectotype has the same collection information as in the protologue of Cooke (referenced by Saccardo) and is dated October 1887, while the protologue was published in December 1887, so it clearly forms part of the original material.

Heterotypic synonyms:

• Hebeloma fusipes Bres., Bollettino della Società Botanica Italiana 1: 196 (1892)
• Hebeloma gigaspermum Gröger & Zschiesch., Z. Mykol. 47 (2): 201 (1981)
• Hebeloma groegeri Bon, Documents Mycologiques 31 (123): 27 (2002)
• Hebelomatis fusipes (Bres.) Locq., Flore Mycologique Vol III - Text. Cortinariales A: 146 (1979) ["1977"]

Homotypic synonyms:

• Agaricus nauseosus Cooke, Grevillea 16 (78): 43 (1887)
• Hebelomatis nauseosum (Sacc.) Locq., Flore Mycologique Vol III - Text. Cortinariales A: 133 (1979) ["1977"]

• arrow_drop_downarrow_drop_upEtymology
  From nauseus– nauseous, to describe the odour which Cooke found to be “very strong and abominable, especially after being kept a night in a box”.

• arrow_drop_downarrow_drop_upDiagnosis
  Cooke Grev. XVI, p. 43. Fetid. Pileus convex, gibbous, more or less expanded, even, smooth, viscid, ochrey-white (1–1.5 inch [2.5–4 cm] across). Stem equal, or slightly attenuated below, of the same colour, mealy above, faintly striate downwards, and in decay turning black at the base, solid. Gills ventricose, sinuate behind, very broad, rather distant, pallid, then clay coloured, at length ferrugineous. Spores large, attenuated towards each end, 20 × 10 μm. On the ground in mixed woods. Park End, Forest of Dean, near Bristol. This is evidently distinct from A. capniocephalus and A. ichnostylus. The odour is very strong and abominable, especially after being kept a night in a box.

Description

Description of Hebeloma nauseosum based on 35 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (11) 16–44 (60) mm diameter; shape often convex, occasionally broadly umbonate or umbonate, rarely none or strongly umbonate; characters occasionally spotting, rarely hygrophanous; margin characters usually smooth, occasionally involute, rarely reflexed or serrate; viscosity tacky when moist; colour variation usually unicolour, rarely two color; colour at centre occasionally dark pinkish buff, rarely clay-buff, cream, honey, cinnamon, yellowish brown, pale cream, pale pinkish buff, dark greyish buff, pinkish buff, pale yellow, ochraceous or buff-yellow.

  Lamellae: attachment usually emarginate, occasionally adnate, rarely decurrent tooth; maximum depth 2–8 mm; number of complete lamellae 25–46; presence of tears absent; white fimbriate edge occasionally absent, weak or present.

  Cortina presence: no.

  Stipe: (12) 24–69 (100) x (2) 3–7 (11) {median} x (2) 3–8 (12) {basal} mm; stipe Q 4.0–18.3; base shape usually cylindrical, occasionally clavate or tapering, rarely subbulbous; floccosity often fibrillose, occasionally pruinose, rarely floccose or pruinose at apex; rooting usually no, rarely yes or weak; thick rhizoids at base absent;

  Context: Texture firm; stipe interior usually hollow, occasionally stuffed; stipe flesh discolouring often yes, rarely no, weak or very strongly; slenderness measure 4.5–35.8; smell sacchariolentia, usually sweet, rarely cocoa, soap or raphanoid; taste often weakly bitter, occasionally mild where recorded.

  Spore deposit colour: often brownish olive, occasionally umber, rarely clay-buff.

  Exsiccata characters: occasionally lamellae blackening, pileus blackening, stipe blackening or dark, rarely hard.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, often limoniform, rarely fusoid; colour in microscope usually brown, occasionally yellow brown; guttules often yes, occasionally no, rarely weak. papilla often yes, occasionally very strongly or weak; Spore Code: (O2) O3; P1 P2; D3 D4.

  Basidia: (27) 31–45 (47) x 7–12 μm; ave. Q 3.3–4.5; spore arrangement 4 spored;

  Cheilocystidia: main shape usually cylindrical, occasionally balloon-shaped, gently clavate, clavate, clavate-lageniform or clavate-ventricose or ventricose, rarely capitate, capitate-stipitate, clavate-stipitate, utriform or lageniform; special features observed occasionally septa, short, clamped septa, irregular or median thickening, rarely branching, many collapsed in exsiccata, rostrate, sparse, stipitate or tapering; cheilocystidia ratios: A/M = 0.94–2.68; A/B = 0.83–3.62; B/M = 0.60–1.34.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 120 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis often ellipsoid, occasionally cylindrical or thickly sausage-shaped up to 30 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 50 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma nauseosum's preferred habitat appears to be deciduous woodland or deciduous slagheap bog with decomposed litter or litter. Where only one possible associate was recorded, the most commonly recorded associate was Salix (61.9%) but Quercus (23.8%), Populus (9.5%) and Tilia (4.8%) were also recorded. In these cases the most commonly recorded families were Salicaceae (68.2%) and Fagaceae (27.3%). We have additional records where Betula (15.2%), Alnus (12.1%), Corylus (6.1%), Castanea (3.0%), Fagus (3.0%), Carpinus (3.0%) and Pinus (3.0%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Salicaceae (66.7%), Fagaceae (30.3%) and Betulaceae (30.3%) The growth habit of our collections was often scattered, occasionally caespitose or solitary and rarely gregarious.

  According to our current collections, the species is found only in Europe. On the continent, collections has 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 (64.7%) and mediterranean forests, woodlands & scrub (26.5%), specifically including the ecoregions: European Atlantic mixed forests (32.4%) and Italian sclerophyllous and semi-deciduous forests (20.6%). From collector information, it appears collections have been found in the 1.4 Forest – Temperate (36.4%), 17.1 Quarry (31.8%) and 14.5 Urban Areas (18.2%) 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 Southwest (France and Spain), the Centre (Belgium and Germany), the Southeast (Italy and Malta) and the North (Sweden, Denmark, Wales, Finland, Norway and England). Specimens have been collected from 35.9°N to 60.1°N.

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma nauseosum is molecularly distinct and forms well supported monophyletic clades in phylogenetic analyses of all loci tested. The species can be identified molecularly with any one of ITS, V6, RPB2 or Tef1a. Within the H. nauseosum clade of theV9 result two well supported subclades are retrieved, which cannot be matched with any other character, neither morphological or molecular. In phylogenetic terms the closest relatives of H. nauseosum appear to be H. sacchariolens and H. odoratissimum. We obtained the ITS2 from the type of H. gigaspermum which supports the synonymization of the former with the clade of H. nauseosum. There are no ITS sequences from outside Europe published to date that are likely to belong to this species.

• arrow_drop_downarrow_drop_upCommentary
  The smell associated with Hebeloma nauseosum immediately places it in H. sect. Sacchariolentia. The spore width, on average at least 7.5 μm, means it can only be H. nauseosum or H. odoratissimum. Whereas H. nauseosum does tend to have larger spores than H. odoratissimum, there is considerable overlap so this is not the best character on which to separate these two taxa. A better character is the nature of the pileus. Hebeloma odoratissimum has a tomentose or velutinate pileus that often cracks into small scales, giving a squamulose look to the pileus, and a thin ixocutis at most 70 μm thick. Hebeloma nauseosum, on the other hand, has a smooth pileus, at most slightly velutinate at the margin, and with ixocutis from 100–120 μm. In the protologue of his Agaricus nauseosus, Cooke specifically mentions the strong smell and the large spores. While the spore size he gives of 20 × 10 μm is larger than typical for this taxon, there is no other sweet smelling Hebeloma. known from Europe that has such large spores. We have searched extensively, particularly at K, for any original material, but we failed to locate any. Nonetheless, with his diagnosis and the plate 963, which corresponds to the collection in his diagnosis, we are satisfied that this taxon is synonymous with both H. fusipes and H. gigaspermum, for both of which we have examined the holotype material and, indeed, we have included these two collections within our overall description of this species. We did consider the possibility of trying to conserve one of these two names against the older name H. nauseosum, but we felt that there would be little to gain from the perspective of nomenclatural stability. Both names, H. fusipes and H. gigaspermum, are in use, see for instance Vesterholt (2005), and while H. gigaspermum is probably more widely used, H. fusipes is the older name of these two, and neither is recorded with great regularity. We did originally believe that these two taxa, H. fusipes and H. gigaspermum, were different species. We thought that H. gigaspermum was a North European taxon associated with Salix in damp habitats, while H. fusipes was a Southern European taxon (with smaller spores) associated with Quercus, specifically on rich calcareous soil. However, we noted on our database that we were finding collections that did not match this separation and then we also failed to find any molecular difference. Hence we believe all three names are conspecific and accordingly we synonymize them here.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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