Hebeloma marginatulum (Photo: J. Vesterholt)

Taxonomy

Basionym:
Hebeloma versipelle var. marginatulum J. Favre, Ergebnisse der Wissenschaftlichen Untersuchungen der des Schweizerischen Nationalparks 5 (Neue Folge) (33): 202 (1955)

Types: SWITZERLAND: Graubunden, Costainas, Haut Val S-charl (approx. 46.61°N, 9.57°E, alt. approx. 2400 m a.s.l.) in alpine meadow under Salix herbacea, 24 Aug. 1947, J. Favre (Lectotype. herbarium acc. no. G K13929, HJB1000055). Lectotype designated by Beker et al., Hebeloma (Fr.) P. Kumm.: (2016) page 142 (MBT202545).

Heterotypic synonyms:

• Hebeloma polare Vesterh., Nord. J. Bot. 9 (3): 305 (1989)
• Hebeloma aggregatum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 30 (1983)
• Hebeloma griseovelatum A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 125 (1983)
• Hebeloma ollaliense A.H. Sm., V.S. Evenson & Mitchel, The Veiled Species of Hebeloma in the Western United States: 31 (1983)

• arrow_drop_downarrow_drop_upEtymology
  From marginatus– with a margin or border, perhaps emphasizing the thin paler margin that is common for this species and was noted by Favre in his original description.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  A typo differt statura minore, pileo non expanso, minus viscoso, lamellis parcis, latioribus, sporis leviter majoribus.

• arrow_drop_downarrow_drop_upEnglish translation
  Differs from the type by the smaller habit; non expanding pileus which is less viscous; less, and broader lamellae, and slightly larger spores.

Description

Description of Hebeloma marginatulum based on 181 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (9) 14–36 (47) mm diameter; shape occasionally umbonate, convex or broadly umbonate, rarely papillate or strongly umbonate; characters often remains of universal veil, occasionally hygrophanous, rarely pruinose; margin characters usually smooth, rarely involute, crenulate or fibrillose; viscosity tacky when moist; colour variation often unicolour, occasionally two color; colour at centre occasionally sepia or yellowish brown, rarely umber, fuscous, dark brick, cinnamon, ochraceous, brownish olive, dark greyish buff, dark fawn or fawn.

  Lamellae: attachment usually emarginate, rarely adnate, adnexed or decurrent tooth; maximum depth 3–8 mm; number of complete lamellae 31–48; presence of tears usually absent, rarely visible with x10 lens; white fimbriate edge often present, occasionally weak, rarely absent.

  Cortina presence: yes.

  Stipe: (13) 17–38 (60) x (2) 3–5 (8) {median} x (1) 3–6 (8) {basal} mm; stipe Q 2.6–20.0; base shape usually cylindrical, occasionally clavate, rarely tapering; floccosity often fibrillose, occasionally fibrous or pruinose at apex, rarely floccose at apex, pruinose or tomentose; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior hollow, rarely superior wick or stuffed; stipe flesh discolouring often yes, occasionally no, rarely weak; slenderness measure 1.7–57.1; smell occasionally raphanoid or odourless, rarely weakly raphanoid, strongly raphanoid, cocoa or earthy; taste occasionally none or bitter, rarely weakly bitter, raphanoid or weakly raphanoid where recorded.

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

  Exsiccata characters: Not recorded.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape usually ellipsoid, often ovoid or amygdaloid, rarely cylindrical; colour in microscope often yellow, occasionally brown; guttules often no, occasionally yes. papilla no; Spore Code: O1 (O2); P0; D0 (D1).

  Basidia: (20) 22–36 (37) x 6–9 μm; ave. Q 2.8–4.5; spore arrangement 4 spored;

  Cheilocystidia: main shape usually ventricose or lageniform, occasionally clavate or cylindrical, rarely clavate-lageniform or clavate-ventricose, lentiform or pyriform; special features observed often septa, occasionally geniculate, rarely bifurcate, irregular, many collapsed in exsiccata, rostrate, apical thickening, basal thickening, branching, clamped septa, median thickening, subcapitate or yellow contents; cheilocystidia ratios: A/M = 1.01–1.47; A/B = 0.53–0.95; B/M = 1.55–2.33.

  Pleurocystidia: usually none seen, rarely seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 100 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation often no, occasionally yes; shape of trama elements beneath subcutis ellipsoid or thickly sausage-shaped, occasionally pyriform up to 20 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 150 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma marginatulum's preferred habitat appears to be arctic tundra pastureland or arctic tundra. Where only one possible associate was recorded, the most commonly recorded associate was Salix (95.9%) but Dryas (1.6%) and Betula (1.6%) were also recorded. In these cases the most commonly recorded family was Salicaceae (95.8%). We have additional records where Alnus (1.4%) and Picea (1.4%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Salicaceae (94.4%) and Betulaceae (9.2%) The growth habit of our collections was often scattered, occasionally solitary and rarely caespitose or gregarious.

  According to our current data, the species is found on multiple continents with collections found in Northern America (53.6%), Europe (38.1%) and Temperate Asia (8.3%). 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 (42.5%), temperate conifer forests (33.1%) and unknown biome (17.7%), specifically including the ecoregions: Colorado Rockies forests (19.9%), Kalaallit Nunaat Arctic steppe (18.2%), Unknown region (17.7%) and Russian Arctic desert (12.7%). From collector information, it appears collections have been found in the 4.1 Grassland – Tundra (52.5%) and 5.11 Wetlands (inland) – Alpine wetlands (inc. temporary waters from snowmelt) (35.8%) 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 Northern America we have records from Subarctic America (Greenland and Nunavut), Northwestern U.S.A. (Colorado, Montana, Wyoming and Oregon), Eastern Canada (Newfoundland and Labrador) and Western Canada (British Columbia).

  Within Europe we have records from the North (Svalbard, Norway, Finland, Iceland and Faroe Islands), the Centre (Switzerland, Austria and Poland), the Southwest (France) and the Southeast (Italy). Specimens have been collected from 42.8°N to 78.9°N.

  Within Temperate Asia we have records from Russian Far East (Chukotka) and Siberia (Tyumen and Krasnoyarsk).

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma marginatulum has excellent bootstrap support in the five-locus analysis and in the V6, RPB2 and Tef1a results. In the V9 result the species is monophyletic, but not supported by bootstrap ≥ 80% and in the ITS result it is what we call non-discordant and included in the multi-species clade around H. mesophaeum. It appears that the ITS is the least well suited for species identification of H. marginatulum, of all loci tested. We have an ITS sequence of the type of H. polare and as far as ITS permits it supports the synonymization of H. polare with our concept of H. marginatulum, although we did not manage to obtain the ITS of the lectotype of the latter species.

• 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 (but clearly) dextrinoid ellipsoid spores, although some may be amygdaloid or ovoid, and spores usually greater than 10 μm long and 6 μm wide and growing in alpine or arctic habitats with Salicaceae, this species can only be confused with H. dunense which can occur in the same habitats. We have already discussed the difficulty of separating these two taxa morphologically in our commentary and discussion of H. dunense. We do suspect that many collections of H. dunense in arctic or alpine habitats have been incorrectly determined as H. marginatulum, since it is only recently that we have become aware of the existence of H. dunense in these arctic and alpine habitats. Hence when examining herbarium material of this taxon one should be wary of confusion. Vesterholt (1989) described H. polare as a new species distinct from H. marginatulum, on the basis of its larger size, very dark colours and slightly different cystidia. Both microscopically and molecularly we cannot find any support for this separation and macroscopically we do have what appears to be a continuous range, both in colour and size. We have therefore synonymized these two taxa. Hebeloma marginatulum is very common in both arctic and alpine habitats and we suspect that it is circumpolar. We should note that we do have a collection from Greenland where there did exist pleurocystidia. While we have never noticed pleurocystidia in our European collections, we should not rule out that they may occasionally exist.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

Image gallery