Hebeloma nigellum (Photo: J. Vesterholt)

Taxonomy

Types: FRANCE: Savoie, Leon Gromier (Vanoise;Savoie) (approx. 45.4165°N, 6.7328°E, alt. approx. 2385 m a.s.l.) on acidic, mossy soil in alpine meadow under Salix herbacea, 16 Sep. 1966, G. Bruchet (Holotype. herbarium acc. no. LY BR66-71, HJB1000042).

Heterotypic synonyms:

• Hebeloma atrobrunneum Vesterh., Nord. J. Bot. 9 (3): 311 (1989)
• Hebeloma kuehneri Bruchet [as “Kühneri”], Bull. Mens. Soc. Linn. Lyon 39, supplement 6: 125 (1970)
• Hebelomatis kuehneri (Bruchet) Locq., Flore Mycologique Vol III - Text. Cortinariales A: 146 (1979) ["1977"]

• arrow_drop_downarrow_drop_upEtymology
  From nigellus– blackish, describing the dark coloured pileus.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  Hebeloma nigellum sp. nov. - Cortina manifesta, in adultis subspecie vestigiorum annuliformium persistente; pileo usque ad 17 mm lato, saturatissimo, e nigello murine vel obscurissime ex atro brunneo, parum expanso, carne crassiuscula, obscure e rubida brunnea; stipite 13–21 x 2–2,5 mm, in adultos obscure e subolivaceo brunneo; lamellis siccis, parum stipatis; odore in speciminibus recenter collectis nullo. Sporis 11–13 x 6,5–7 μm, amygdaliformibus ac rugosis; pilis marginum inferne ad 8–10 μm inflatis. Species in litoribus muscosis rivulorum montium, inter Salices herbaceas crescit.

• arrow_drop_downarrow_drop_upEnglish translation
  Cortina manifestly present, in mature specimens visible as a cortina connecting the margin of the pileus and stipe; pileus up to 17 mm broad, intensely pigmented greyish black or very dark blackish brown, weakly expanding, context thick-fleshed, dark reddish brown; stipe 13–21 × 2–2.5 mm, in mature specimens dark brown with olivaceous tinge; lamellae dry, not very crowded; smell in recently collected specimens none. Spores 11–13 × 6.5–7 μm, amygdaloid and rugose; marginal hairs broadened towards base up to 8–10 μm wide. Growing in the borders of mossy marshes in the mountains, among Salix herbacea.

Description

Description of Hebeloma nigellum based on 72 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (7) 9–28 (33) mm diameter; shape usually convex, occasionally umbonate, rarely papillate or strongly umbonate; characters occasionally remains of universal veil; margin characters occasionally involute or smooth, rarely reflexed; viscosity tacky when moist; colour variation often two color, occasionally unicolour; colour at centre occasionally dark brick, umber or greyish brown.

  Lamellae: attachment often emarginate, occasionally adnate or adnexed; maximum depth 2–6 mm; number of complete lamellae 20–36; presence of tears often absent, rarely visible with x10 lens or visible with naked eye; white fimbriate edge often weak, occasionally present, rarely absent.

  Cortina presence: yes.

  Stipe: (9) 11–44 (50) x 1–3 (4) {median} x 1–3 (4) {basal} mm; stipe Q 6.0–18.7; base shape cylindrical; floccosity usually fibrillose, occasionally pruinose at apex or floccose at apex; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior hollow, occasionally stuffed; stipe flesh discolouring often yes, occasionally no, rarely very strongly; slenderness measure 9.1–25.3; smell occasionally raphanoid, odourless or weakly raphanoid; taste often weakly bitter or raphanoid, occasionally bitter or weakly raphanoid where recorded.

  Spore deposit colour: umber.

  Exsiccata characters: occasionally pileus blackening, rarely dark or rich brown color.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, occasionally ovoid or ellipsoid; colour in microscope occasionally yellow or yellow brown, rarely brown, brown yellow or grey yellow; guttules often no, occasionally yes, rarely weak. papilla usually no, occasionally weak; Spore Code: O1 O2; P0; D2 D3.

  Basidia: (21) 23–40 (45) x (6) 7–11 μm; ave. Q 2.9–4.0; spore arrangement 4 spored;

  Cheilocystidia: main shape lageniform, usually ventricose, occasionally cylindrical, rarely clavate or filiform; special features observed occasionally septa, apical thickening, many collapsed in exsiccata, clamped septa or geniculate, rarely sparse, basal thickening or stipitate; cheilocystidia ratios: A/M = 0.92–1.41; A/B = 0.45–0.89; B/M = 1.45–2.30.

  Pleurocystidia: usually none seen, rarely seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 75 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation usually yes, occasionally no; shape of trama elements beneath subcutis usually thickly sausage-shaped, occasionally angular, ellipsoid or polygonal up to 15 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 140 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma nigellum's preferred substrate appears to be boggy soil. Where only one possible associate was recorded, the most commonly recorded associate was Salix (98.0%) but Alnus (2.0%) were also recorded. In these cases the most commonly recorded family was Salicaceae (98.0%). We have additional records where Betula (11.5%), Quercus (3.3%), Picea (1.6%) and Populus (1.6%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Salicaceae (98.4%) and Betulaceae (14.8%) The growth habit of our collections was usually scattered and rarely solitary.

  According to our current data, the species is found on multiple continents with collections found in Europe (54.2%), Northern America (40.3%) and Temperate Asia (5.6%). 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. tundra (35.7%), temperate broadleaf & mixed forests (30.0%) and temperate conifer forests (15.7%), specifically including the ecoregions: Kalaallit Nunaat Arctic steppe (24.3%). From collector information, it appears collections have been found in the 4.1 Grassland – Tundra (27.9%), 5.11 Wetlands (inland) – Alpine wetlands (inc. temporary waters from snowmelt) (18.0%), 1.4 Forest – Temperate (13.1%) and 5.10 Wetlands (inland) – Tundra wetlands (inc. pools and temporary waters from snowmelt) (13.1%) 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 (Denmark, Norway, England, Finland, Iceland, Sweden and Scotland), the Centre (Belgium and Switzerland) and the Southwest (France). Specimens have been collected from 45.4°N to 69.3°N.

  Within Northern America we have records from Subarctic America (Greenland and Nunavut) and Northwestern U.S.A. (Wyoming and Colorado).

  Within Temperate Asia all our records are from Siberia (Tyumen).

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma nigellum is paraphyletic in all single locus analyses, but gets moderate bootstrap support in the five locus result. The species belongs to the clade with H. clavulipes, H. hygrophilum, H. monticola, H. oreophilum and H. petsbergense, for all of which it might be mistaken based on ITS data. We do have ITS data from the type of H. nigellum and the lectotype of H. kuehneri, which occur alongside the majority of H. nigellum collections in the (not-bootstrap-supported) tail of the multi-species clade around H. clavulipes.

• 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, it can be differentiated on the basis of the amygdaloid (and some ellipsoid or ovoid), but rarely limoniform spores distinctly to rather strongly dextrinoid, always less than 15 μm long, but always at least 7 μm wide, and the number of lamellae always less than 40. The nearest species both morphologically and molecularly are H. fuscatum, which also occurs in arctic and alpine regions,but has a distinct papilla on the spores giving many a limoniform appearance, H. spetsbergense, also an arctic species (known only from Svalbard) with longer spores and H. hygrophilum, also occurring with Salix in non-arctic and non-alpine areas but with narrower spores. It is quite unusual, but not unique, to have the same Hebeloma taxon occurring in both arctic and alpine and lowland areas of lower latitude. (Hebeloma dunense and H. mesophaeum are also examples.) Indeed Vesterholt (1989) erected H. atrobrunneum as he believed that H. nigellum was restricted to arctic and alpine areas. There are certainly some differences in pileus colour, with the arctic, alpine collections occasionally (but not always) being more unicoloured and perhaps somewhat darker in the centre. There is also a (minor) difference in the thickness of the epicutis. But we see no other morphological difference and have found no consistent molecular difference. Hence the synonymy that Vesterholt (2005) established between Hebeloma nigellum and H. atrobrunneum is maintained. With regard to H. kuehneri, this species was established (as “H. Kühneri”) in the same paper as H. nigellum. Bruchet saw the primary difference between the two as the colour of the pileus, more grey to black in H. nigellum while with more brown tones in H. kuehneri. Again, we find no significant difference either microscopically or molecularly between these two taxa and from a macroscopic viewpoint we have seen a range of intermediate colours of the pileus. Unfortunately, the holotype of H. kuehneri at LY has been lost. We have therefore proposed one of Bruchet’s paratypes, namely LY BR66-15 (Database Record 11598) as lectotype.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

Image gallery