Hebeloma pallidolabiatum (Photo: H. J. Beker)

Taxonomy

Types: SVALBARD: Skansbukta (78.5156°N, 16.014°E, alt. approx. 35 m a.s.l.) on acidic soil in arctic, coastal tundra under Salix polaris, 14 Aug. 2007, H.J. Beker, M.L. Beker (Holotype. herbarium acc. no. BR BR-MYCO 174908-17 (holotype), C C-F-92312 (isotype), HJB11992).

• arrow_drop_downarrow_drop_upEtymology
  From pallidus– pale and labiatus– of the lip, to emphasise the thin pale margin that appears to be a consistent character of this taxon.

• arrow_drop_downarrow_drop_upDiagnosis
  Hebeloma pallidolabiatum belongs, based on its cheilocystidium shape to H. subsect. Denudata [H. subsect. Crustuliniformia]. It can be separated from the other small arctic species of this section by the cheilocystidium ratio apex : base (A/B) which is always less than 1.8 and the spores, most of which are always quite distinctly ornamented and over 12 µm in length.

Description

Description of Hebeloma pallidolabiatum based on 7 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (12) 14–21 (22) mm diameter; shape often convex or broadly umbonate, occasionally applanate; characters occasionally pruinose or remains of universal veil; margin characters smooth, occasionally involute; viscosity tacky when moist; colour variation often unicolour or two color; colour at centre often sepia, rarely greyish brown, dark brick or brownish olive.

  Lamellae: attachment emarginate; maximum depth up to 3 mm; number of complete lamellae 26–39; presence of tears usually absent, occasionally visible with naked eye; white fimbriate edge usually present, occasionally very strong.

  Cortina presence: no.

  Stipe: (10) 12–28 (30) x 2–6 (7) {median} x 2–6 (7) {basal} mm; stipe Q 2.5–9.0; base shape cylindrical, occasionally clavate; floccosity often pruinose at apex, occasionally fibrillose, pruinose or velute; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior often hollow, stuffed or superior wick; stipe flesh discolouring variable; slenderness measure 2.3–14.4; smell often odourless, occasionally raphanoid; taste Not recorded.

  Spore deposit colour: often yellowish brown or brownish olive.

  Exsiccata characters: Not recorded.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, often limoniform; colour in microscope usually brown, occasionally brown yellow or yellow brown; guttules yes. papilla yes; Spore Code: O2; P0; (D1) D2.

  Basidia: (24) 25–43 (45) x 6–10 μm; ave. Q 3.6–4.5; spore arrangement 4 spored;

  Cheilocystidia: main shape usually clavate-stipitate, often clavate-lageniform or clavate-ventricose, rarely capitate-stipitate, gently clavate or cylindrical; special features observed often septa or clamped septa; cheilocystidia ratios: A/M = 1.40–2.05; A/B = 1.19–1.69; B/M = 1.18–1.30.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 80 μm; ixocutis hyphae width up to 5 μm; ixocutis hyphae encrustation yes; shape of trama elements beneath subcutis ellipsoid or isodiametric, often thickly sausage-shaped or thinly sausage-shaped up to 20 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 90 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma pallidolabiatum's preferred habitat appears to be arctic tundra. Where only one possible associate was recorded, that associate has always been Salix (family Salicaceae). We have additional records where Dryas 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 (100.0%) and Rosaceae (14.3%) The growth habit of our collections was usually scattered and occasionally gregarious or solitary.

  According to our current data, the species is found on multiple continents with collections found in Northern America (57.1%) and Europe (42.9%). 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. unknown biome (57.1%) and tundra (42.9%), specifically including the ecoregions: Unknown region (57.1%), Russian Arctic desert (28.6%) and Canadian Middle Arctic Tundra (14.3%). From collector information, it appears collections have been found only in the 4.1 Grassland – Tundra IUCN habitat 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 Northern America all our records are from Subarctic America (Nunavut).

  Within Europe all our records are from the North (Svalbard). Specimens have been collected from 78.5°N to 79.0°N.

• arrow_drop_downarrow_drop_upMolecular results
  The sequences of the two Hebeloma pallidolabiatum collections are monophyletic in five out of six tested loci and supported by bootstrap in four of them. The ITS is the least suited for species identification. Two ITS sequences were obtained from the type collection, of which one is included in a H. pallidolabiatum clade and the other is part of the unresolved alpinum-complex part of the tree.

• arrow_drop_downarrow_drop_upCommentary
  Given the shape of its cheilocystidia, Hebeloma pallidolabiatum clearly belongs to H. subsect. Crustuliniformia and was most likely not included in the intercompatibility tests of Aanen & Kuyper (1999). This taxon is macroscopically very similar to H. minus and it is likely that in the past it has been confused with this species. It can be distinguished from this species by the cheilocystidium ratio A/B which is at most 1.8; the cheilocystidia tend, on average, to be more swollen towards the base and less swollen towards the apex resulting in a lower ratio between these two measurements. Additionally, the spores of H. pallidolabiatum are on average larger than those of H. minus, which can be seen best in measurements of the spore area. Hebeloma pallidolabiatum is also morphologically and molecularly in some loci, including ITS, close to H. alpinum and these two are difficult to separate microscopically. It can normally be separated from H. alpinum on macroscopic characters, since H. pallidolabiatum is smaller with a darker coloured pileus and with fewer lamellae than H. alpinum. With regard to the other alpine/arctic species, 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. pallidolabiatum is always greater than 8.5 μm. It can be distinguished from H. louiseae by the cheilocystidium ratio A/B being at most 1.8. The separation from H. perexiguum is straightforward as the spores for H. pallidolabiatum are more ornamented and longer. Given the small number of collections on which our description is based, it is possible that our description is too narrow, but until more collections of this taxon are recorded we cannot be sure.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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