Hebeloma minus (Photo: H. J. Beker)

Taxonomy

Types: FRANCE: Savoie, Lac des Assiettes,Col de la Vanoise (approx. 45.389°N, 6.792°E, alt. approx. 2500 m a.s.l.) on acidic soil in alpine meadow under Salix herbacea, 11 Sep. 1969, G. Bruchet (Holotype. herbarium acc. no. LY BR69-15, HJB1000065).

Homotypic synonyms:

• Hebelomatis minus (Bruchet) Locq., Flore Mycologique Vol III - Text. Cortinariales A: 146 (1979) ["1977"]

• arrow_drop_downarrow_drop_upEtymology
  From minus– less, to emphasise the small stature of this mushroom.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  Hebeloma minus sp. nov. - Cortina nulla; pileo parvo, usque ad 16 mm, plerumque medio colorato, e luteo brunneo vel cinnamomeo, in margine brunneolo vel albido, margine ac marginella saepe expansa; stipite 11–20 x 2–2,5 mm, albido, sub lamellis dense pruinoso ac inferius farinoso; lamellis siccis vel sublacrymantibus (guttulis limpidis); odore nullo. Sporis 12–15 x 6–7 μm, majoribus, amygdaliformibus, in papillam superne elongatis, ectospora s.m. opt, non apparente; pilis marginum summis dilatatis (8–10 μm), interdum inferne ad 7–8 μm inflatis. Species alpina, inter Salices herbaceas crescit.

• arrow_drop_downarrow_drop_upEnglish translation
  Cortina absent; pileus small, up to 16 mm broad, usually medium coloured, yellowish brown to cinnamon, with brownish to whitish margin; margin and outermost margin expanded; stipe 11–20 × 2–2.5 mm, whitish, densely pruinose between lamellae, in lower part farinose; lamellae dry and indistinctly beaded with clear guttules; smell none. Spores 12–15 × 6–7 μm, large, amygdaloid, with elongate papilla at apex; ectosporium under the microscope not distinct; marginal hairs with broadened apex (8–10 μm), sometimes inflated in lower part (up to 7–8 μm). Alpine species, growing between Salix herbacea.

Description

Description of Hebeloma minus based on 27 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (7) 10–25 (31) mm diameter; shape occasionally convex, umbonate or broadly umbonate, rarely strongly umbonate; characters occasionally remains of universal veil, rarely hygrophanous or rimulose; margin characters usually smooth, occasionally involute, rarely ribbed; viscosity tacky when moist; colour variation often two color, occasionally unicolour; colour at centre occasionally yellowish brown or umber, rarely orange-brown, clay-buff, brownish olive, dark pinkish buff or sepia.

  Lamellae: attachment emarginate, rarely adnate; maximum depth 2–5 mm; number of complete lamellae 26–40; presence of tears often absent, occasionally visible with x10 lens or visible with naked eye; white fimbriate edge often present, occasionally weak.

  Cortina presence: no.

  Stipe: (10) 13–31 (40) x (1) 2–5 (8) {median} x (1) 2–8 (10) {basal} mm; stipe Q 3.3–20.0; base shape usually cylindrical, occasionally clavate, rarely bulbous; floccosity often pruinose, occasionally pruinose at apex, fibrillose or floccose, rarely weakly floccose; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior often stuffed, occasionally hollow; stipe flesh discolouring usually no, rarely weak; slenderness measure 3.4–28.0; smell occasionally odourless, weakly raphanoid or raphanoid, rarely strongly raphanoid; taste mild, often weakly bitter or weakly raphanoid where recorded.

  Spore deposit colour: often yellowish brown or brownish olive.

  Exsiccata characters: often fragile or shiny.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, occasionally limoniform; colour in microscope occasionally brown, brown pale or yellow brown, rarely brown yellow or yellow; guttules often yes, occasionally no, rarely weak. papilla often yes, occasionally no, rarely weak; Spore Code: O2 O3; P0 P1 (P2); D1 D2.

  Basidia: 27–40 (41) x 7–11 μm; ave. Q 2.8–4.1; spore arrangement 4 spored;

  Cheilocystidia: main shape usually clavate-stipitate, often capitate-stipitate, occasionally clavate-lageniform or clavate-ventricose or spathulate-stipitate, rarely capitate, lageniform or subcapitate; special features observed occasionally apical thickening, median thickening or septa, rarely clamped septa, irregular, geniculate, many collapsed in exsiccata or sinuate; cheilocystidia ratios: A/M = 1.87–2.67; A/B = 1.45–3.02; B/M = 0.79–1.53.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 100 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation variable; shape of trama elements beneath subcutis often circular, ellipsoid, thickly sausage-shaped or spherical, occasionally cylindrical up to 30 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 100 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma minus's preferred habitat appears to be arctic tundra with mossy soil. Where only one possible associate was recorded, the most commonly recorded associate was Salix (94.7%) but Dryas (5.3%) were also recorded. In these cases the most commonly recorded families were Salicaceae (94.7%) and Rosaceae (5.3%). We have additional records where Polygonum was recorded as a possible associate, but for these collections a number of possible associates were mentioned. Overall the most commonly recorded families are Salicaceae (95.0%) and Rosaceae (10.0%) 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 (66.7%) and Northern America (33.3%). 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 (48.1%), unknown biome (22.2%), temperate conifer forests (14.8%) and boreal forests/taiga (11.1%), specifically including the ecoregions: Unknown region (22.2%), Russian Arctic desert (18.5%), Canadian Middle Arctic Tundra (18.5%), Alps conifer and mixed forests (14.8%) and Iceland boreal birch forests and alpine tundra (11.1%). From collector information, it appears collections have been found in the 4.1 Grassland – Tundra (74.1%) and 5.11 Wetlands (inland) – Alpine wetlands (inc. temporary waters from snowmelt) (14.8%) 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 (Svalbard and Iceland), the Centre (Switzerland), the Southwest (France) and the Southeast (Italy). Specimens have been collected from 45.4°N to 78.9°N.

  Within Northern America we have records from Subarctic America (Nunavut and Greenland) and Eastern Canada (Newfoundland and Labrador).

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma minus is monophyletic but not supported by bootstrap ≥ 80% (75%) in five- and six-locus analyses. Like H. alpinum, H. minus is a rather diverse species molecularly. The only single loci in which all available H. minus sequences form a supported monophyletic clade are RPB2 and Tef1a. In other single locus analyses, H. minus forms mixed clades with either H. louiseae or H. pallidolabiatum or some of the H. minus sequences are included in the unresolved alpinum-complex part of the tree; Eberhardt et al. 2015a).

• arrow_drop_downarrow_drop_upCommentary
  Given the shape of its cheilocystidia, Hebeloma minus clearly belongs to H. subsect. Crustuliniformia and most likely corresponds to ICG7 of Aanen & Kuyper (1999). It appears morphologically and molecularly close to H. alpinum and these two taxa are difficult to separate microscopically. Hebeloma minus can normally be distinguished from H. alpinum on macroscopic characters, since H. minus is smaller with a darker coloured pileus and with fewer lamellae than H. alpinum. Hebeloma minus is also macroscopically very similar to H. pallidolabiatum, but can be separated microscopically using the cheilocystidium ratio A/B which is always > 1.8 for H. minus but < 1.8 for H. pallidolabiatum. With regard to the other alpine/arctic species from H. sect. Denudata, it can be distinguished from H. aurantioumbrinum through the average width of the cheilocystidia apex which never exceeds 8.5 μm for H. aurantioumbrinum, while the average cheilocystidium apex for H. minus is always greater than 8.5 μm. It can be separated from H. louiseae, which has spores O1 or O2 and very rarely O3, while H. minus has many spores O3. In subalpine areas it is most closely related to H. salicicola and H. pusillum. But H. pusillum has ave. spore Q greater than 1.9, while H. minus ave. spore Q never exceeds 1.9 and H. salicicola has spores D2 or even D3, while H. minus spores are usually D1 and rarely even D2.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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