Hebeloma subtortum (Photo: H. J. Beker)

Taxonomy

Types: FINLAND: Tavastia australis, Tammela Municipality, Mustiala, Runkomaki (approx. 60.82°N, 23.77°E, alt. approx. 80 m a.s.l.) in woodland roadside, 9 Aug. 1889, P.A. Karsten (Lectotype. herbarium acc. no. H4006, HJB1000157). Lectotype designated by Vesterholt, Nord. J. Bot. 9 (3): (1989) page 296.

Heterotypic synonyms:

• Agaricus exalbidus f. vernalis Britzelm. [as "exambidus"], Botanisches Centralblatt 54 (15-17): 279 (1893)
• Agaricus fastibilis β subumbonatus Schulzer [as "A. (Hebeloma) fastibilis β. subumbonatus"], Verhandlungen der Kaiserlich-Königlichen Zoologisch-Botanischen Gesellschaft in Wien 20: 192 (1870)
• Hebeloma flammuloides Romagn., Sydowia 36: 268 (1947) ["1983"]
• Hebeloma flammuloides var. longiventriosopilis Quadr., Documents mycologiques 14 (56): 31 (1985) ["1984"]
• Hebeloma malenconii Bellú & Lanzoni, Alcune specie mediterranee poco note ritrovate in territorio Italiano 1: 5 (1989)
• Hebeloma mesophaeum var. lacteum Vesterh., Nord. J. Bot. 9 (3): 299 (1989)
• Hebeloma mesophaeum var. ochraceum Bohus, Documents mycologiques 25 (98-100): 87 (1995)
• Hebeloma pallidum Malençon, Champ. Sup. Maroc I. Institut Scientifique Chérifien, Rabat 1: 452 (1970)
• Hebeloma pyrophilum G. Moreno & M.M. Moser, Boletin de la Sociedad Micologia Castellana 8: 79 (1984) ["1983"]
• Hebeloma pyrophilum var. longiventriosopilis (Quadr.) Quadr., Mycol. Helv. 3 (2): 200 (1989) ["1988"]
• Hebeloma sordidum Maire, Bulletin trimestriel de la Société Mycologique de France 30 (2): 212 (1914)
• Hebeloma velatum Velen., Ceske Houby: 390 (1919) ["1920"]

• arrow_drop_downarrow_drop_upEtymology
  From sub– somewhat and tortus– twisted, so somewhat twisted, presumably emphasizing the twisting stipe that Karsten describes in the protologue and that he considers an important character.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  Hatten köttig, tunn, först kullrig, sedan platt, åtminstone i förtone regelbunden, trubbig, slät (utan strimmor), glatt, i början närmast kanten af hyllets lemnigar tilltryckt silkesluden, klibbig eller n. slemmig, blek, often skiftande företrädesvis midten i rödgult, 4–6 cm bred. Foten ihålig, jemntjock, vanl. skrufvriden, tilltryckt fintrådig, i toppen mjölig, hvitaktig, nedtill brandgulaktig, strundom gul- eller brunaktig, 7–9 cm. lång, 0,5–1 cm tjock. Lamellerna fastväxta, n nedlöpande, tättsittande, jembredt lancettlika, hvitaktiga, slutl. lerfärgade, i eggen fint luddnaggande, 2–3 mm. breda. Basiderna cylindriskt klubblika, omkring 30 × 6–7 mmm. Sporerna äggrunda, bruna (under mikr. Höggulaktiga), 7–9 × 4–6 mmm. Cystider inga. Vid väag, m.r. (Mustiala park). 7, 8. Köttet vattigt, n. luktlöst. Utgör nästan en mellamform emellan H. punctatum och H. versipelle, skiljande sig från den senare genom sina smalare fastväxta lameller.

• arrow_drop_downarrow_drop_upEnglish translation
  Pileus fleshy, thin, semiglobose at first, then applanate, regular, at least in the beginning, blunt, smooth (not striate), glabrous, at margin first appressedly silky-tomentose from veil remnants, sticky or somewhat slimy, pale, often turning reddish yellow especially at centre, 4–6 cm broad. Stipe hollow, equal, usually twisted, towards base flame-yellow, in places yellow or brownish, 7–9 cm long, 0.5–1 cm thick. Lamellae adnate, slightly decurrent, crowded, segmentiform, whitish finally leather brown, with finely pruinose edge, 2–3 mm broad. Basidia cyindrical-clavate, about 30 × 6–7 μm. Spores ovoid, brown (under the microscope deep yellow), 7–9 × 4–6 μm. Cystidia none. Along roads, very rare (Mustiala park), July-August. Context cottony, rather odourless. Is almost an intermediate between H. punctatum and H. versipelle, differing from the latter by its narrower, adnate lamellae.

Description

Description of Hebeloma subtortum based on 128 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (18) 26–54 (100) mm diameter; shape often convex, occasionally umbonate, rarely broadly umbonate; characters occasionally remains of universal veil or spotting, rarely pruinose or tomentose; margin characters often smooth, occasionally involute, rarely eroded; viscosity tacky when moist; colour variation usually unicolour, occasionally two color; colour at centre often cream, occasionally pale cream, rarely ochraceous, clay-buff or umber.

  Lamellae: attachment often emarginate, occasionally adnate, rarely adnexed or decurrent tooth; maximum depth 3–8 mm; number of complete lamellae 50–70; presence of tears usually absent, rarely visible with naked eye; white fimbriate edge occasionally weak, present or absent.

  Cortina presence: yes.

  Stipe: (20) 28–83 (130) x (4) 5–13 (20) {median} x (4) 6–13 (20) {basal} mm; stipe Q 2.5–15.8; base shape often cylindrical, occasionally clavate or tapering; floccosity often fibrillose, occasionally pruinose at apex or floccose at apex, rarely none or pruinose; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior usually hollow, occasionally superior wick, rarely stuffed; stipe flesh discolouring often yes, occasionally no, rarely very strongly; slenderness measure 3.1–23.0; smell occasionally raphanoid, odourless or weakly raphanoid, rarely cocoa, earthy or strongly raphanoid; taste often weakly bitter, occasionally bitter, mild or raphanoid where recorded.

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

  Exsiccata characters: occasionally pale, rarely lamellae blackening.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape ellipsoid, usually ovoid; colour in microscope yellow pale, occasionally yellow or grey yellow, rarely very pale, yellow brown or brown pale; guttules variable occasionally weak. papilla no; Spore Code: O1 (O2); P0; D0 (D1).

  Basidia: (16) 22–36 (37) x 5–9 μm; ave. Q 3.2–4.7; spore arrangement 4 spored;

  Cheilocystidia: main shape usually lageniform or ventricose, occasionally cylindrical; special features observed occasionally septa, apical thickening, geniculate or many collapsed in exsiccata, rarely yellow contents, clamped septa, basal thickening, bifurcate, grotesque, median thickening or thick content in neck; cheilocystidia ratios: A/M = 0.90–1.24; A/B = 0.48–0.77; B/M = 1.52–2.43.

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

  Ixocutis: epicutis thickness (measured from exsiccata) up to 300 μm; ixocutis hyphae width up to 7 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis often thickly sausage-shaped, occasionally angular, cylindrical or ellipsoid, rarely oblong up to 15 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 120 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma subtortum's preferred habitat appears to be coniferous woodland with calcareous soil and litter. Where only one possible associate was recorded, the most commonly recorded associate was Pinus (41.7%) but Quercus (23.6%), Castanea (12.5%), Picea (6.9%), Cedrus (5.6%), Fagus (4.2%), Abies (4.2%) and Cistus (1.4%) were also recorded. In these cases the most commonly recorded families were Pinaceae (58.1%) and Fagaceae (40.5%). We have additional records where Betula (4.2%), Tilia (3.1%), Populus (2.1%), Alnus (1.0%), Carpinus (1.0%), Arbutus (1.0%) and Corylus (1.0%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Pinaceae (61.5%), Fagaceae (43.8%), Cistaceae (8.3%) and Betulaceae (6.2%) The growth habit of our collections was often scattered, occasionally caespitose and rarely gregarious or solitary.

  According to our current data, the species is found on multiple continents with collections found in Europe (61.3%), Temperate Asia (20.2%) and Africa (18.6%). On these continents, 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. mediterranean forests, woodlands & scrub (71.8%) and temperate broadleaf & mixed forests (16.9%), specifically including the ecoregions: Canary Islands dry woodlands and forests (14.5%) and Southwest Iberian Mediterranean sclerophyllous and mixed forests (11.3%). From collector information, it appears collections have been found in the 1.4 Forest – Temperate (72.0%) and 1.9 Forest – Subtropical/tropical moist montane (20.7%) 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 (Spain, Portugal, France and Italy), the Centre (Germany, Austria, Belgium, Hungary and Czech Republic), the North (Finland, Sweden, England, Denmark and Norway) and the Southeast (Italy and North Macedonia). Specimens have been collected from 37.1°N to 64.2°N.

  Within Temperate Asia we have records from Western Asia (Cyprus and Turkey), Caucasus (Karachay-Balkar), Eastern Asia (Japan) and China (Xizang).

  Within Africa we have records from Macaronesia (Spain) and Northern Africa (Morocco and Algeria).

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma subtortum is monophyletic and receives 100% bootstrap support in the result of the five-locus dataset. Hebeloma subtortum is part of the clade around H. mesophaeum, with several molecularly not very distinct species, but H. subtortum receives bootstrap support ≥ 80 in the protein coding loci and forms monophyletic subclades in the ITS and V6 results. ITS data does lend support for species synonymization: we were able to amplify the ITS of the types of H. flammuloides, H. pyrophilum and H. mesophaeum var. ochraceum and H. subtortum. All these sequences are included in the ITS cluster of H. subtortum. In spite of that, it is not possible to tell from BLAST searches whether some published data from outside Europe are more likely to belong to H. mesophaeum or H. subtortum.

• 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, with primarily indextrinoid (or indistinctly dextrinoid) ovoid and ellipsoid spores, at most 10 μm long or at most 6 μm wide, this species can only be confused with H. mesophaeum. But 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 icroscope. Hebeloma subtortum has many synonyms, including H. sordidum, a name that has been widely used for this taxon since Vesterholt’s treatment (2005). Vesterholt (1989) did consider H. subtortum to be conspecific with H. mesophaeum, however the number of lamellae is too great for H. mesophaeum and also the stipe width is greater than we would expect for H. mesophaeum; the generation of an ITS sequence for the lectotype has finally verified that it is conspecific with the taxon we regarded as H. sordidum but predates it. We did consider the conservation of the name H. sordidum against H. subtortum, but felt it was unjustified given the usage of the name H. sordidum is relatively recent. We suspect that this taxon has many more synonyms than those we have listed here, but although in many cases we suspect the synonymy, where no material exists, often we cannot totally rule out other possibilities. One of the synonyms is H. pallidum, and both this name and even the name H. sordidum give the impression of a dirty white coloured pileus, which is often the case. But some of our collections from places like Cyprus and the Canary Islands have the pileus much more brightly coloured with some warm brown tones and the lectotype was described as having its centre reddish-yellow.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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