Hebeloma griseopruinatum (Photo: J. Heilmann-Clausen)

Taxonomy

Types: DENMARK: Eskebjerg Veterlyng (55.734°N, 11.2795°E, alt. approx. 0 m a.s.l.) on calcareous soil in grassland under Helianthemum nummularium, 8 Nov. 2009, J. Heilmann-Clausen (C09-174) (Holotype. herbarium acc. no. C C-F-89926 (holotype), BR BR-MYCO 169128-57 (isotype), HJB13422).

• arrow_drop_downarrow_drop_upEtymology
  From griseus– grey and from pruinatus– surface covered with a powdery, in this case, greyish bloom.

• arrow_drop_downarrow_drop_upDiagnosis
  Basidiomes usually in scattered groups. Pileus up to 50 mm in diam., convex or plano-convex with a small but distinct umbo; surface dry or slightly viscid, sometimes with remains of soil and leaves stuck to the pileus, neither hygrophanous nor striate, with a pruinose layer; pruina grey or pale grey, often patchy, in some basidiomes dense and extensive, in others more limited; cuticle colour orange brown; pileus margin straight, slightly involute even in fully grown basidiomes. Lamellae emarginate, moderately spaced (L=40–54); colour cream, alutaceous or brown when young, later tabacine following spore maturity; edge fimbria te, paler than gill surfa ce; lamellules abundant. Stipe central, cylindrical or clavate towards the base, up to 45 × 10 mm and up to 12 mm at the base; white or alutaceous, rarely discolouring brown; surface dry, with fine fibrils and some scattered squamules, concolorous with the surface. Cortina not observed. Flesh rather thin, cream or pale brown, not discolouring when bruised. Smell slight raphanoid component. Spores amygdaloid, with small apiculus and rounded at the end opposite the apiculus, with a distinct thinning of the spore wall and very rarely with any sign of papilla, guttulate with one or more oily drops, almost smooth to very weakly ornamented, with variable loosening of the perispore from no visible sign of loosening to distinctly loosening in a few spores and rather strongly dextrinoid with some spores very strongly dextrinoid (O1/2; P0/1/2; D3/4); spore colour under the microscope from pale brown to yellow brown; spore size based on n=55 pores of the holotype, 5 % to 95 % percentile range 10.6–12.7 × 5.5–6.4 µm, with median 11.5 × 6. 0 µm and avg. 11.6 × 6. 0 µm with S. D. length 0.70 μm and width 0.32 μm, Q value 5 % to 95 % percent ile range 1.77–2. 12, with medi an 1.95 and avg. 1.94 with S. D. 0.11; spore size based on three collections medians 11.0–11.5 × 5.8–6.0 μm and avg. 11.1–11.6 × 5.8–6.0 μm with S. D. length 0.66–0.80 μm and width 0.28–0.32 μm, avg. Q 1.93–1.95. Basidia cylindrical to clavate and 4-spored, 29–39 × 6.7–10.5 μm, with avg. 32–33 × 7.6–8.8 μm. Pleurocystidia not found. Cheilocystidia cylindrical to clavate, the majority constricted in their central region but then swollen again in the lower half but some cylindrical over their entire length; width of apex holotype 5 % to 95 % percentile range 4.8–7.5 μm, with median 6.1 μm and avg. 6.2 μm with S.D. 0.89 μm; across three collections median 5.8–6.2 μm and avg. 5.8–6.3 μm; with n=20–30 selected cheilocystidia of three collections the 5 % to 95 % percentile ranges are 23–46 × 4.6–7.7 × 3.1–5.4 × 4.0–8.2 μm while the averages are 30–35 × 5.8–6.3 × 4.1–4.5 × 5.6–6.5 μm and 30 × 6.2 × 4.1 × 5.6 μm avg. for the holotype. The avg. cheilocystidia ratios for the three collections were: A/M=1.41–1.58; A/B=0.99–1.15; B/M=1.39–1.45. Caulocystidia resemble cheilocystidia but tend to be larger, up to 75 μm long and 13 μm wide at the apex. Pileipellis is an ixocutis with a relatively thick epicutis from 100 μm up to a maximum of 170 μm, embedded hyphae up to 7.5 μm broad, smooth or sometimes encrusted, hyaline or occasionally pigmented. Subcutis made up of orange brown cylindrical to isodiametric elements. Underlying trama contains larger elements up to 17 μm broad. Clamp connections present throughout the fruitbody.

Description

Description of Hebeloma griseopruinatum based on 14 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (16) 26–31 (47) mm diameter; shape often broadly umbonate, occasionally applanate, convex or umbonate; characters often pruinose; margin characters involute; viscosity tacky when moist; colour variation often two color, occasionally unicolour; colour at centre often cinnamon, occasionally clay-buff or orange-brown.

  Lamellae: attachment emarginate; maximum depth up to 10 mm; number of complete lamellae 52–68; presence of tears usually absent, occasionally visible with naked eye; white fimbriate edge often weak, occasionally present, rarely absent.

  Cortina presence: no.

  Stipe: (21) 28–32 (45) x (4) 6–7 (10) {median} x (5) 8–13 (22) {basal} mm; stipe Q 3.5–5.6; base shape often clavate or cylindrical, occasionally bulbous; floccosity usually pruinose at apex, occasionally floccose, velute or pruinose; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior often hollow or stuffed, occasionally superior wick; stipe flesh discolouring often no, occasionally yes or weak; slenderness measure 4.9–6.1; smell occasionally weakly raphanoid, cocoa or raphanoid; taste mild or raphanoid where recorded.

  Spore deposit colour: Not recorded.

  Exsiccata characters: often rich brown color.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, occasionally fusoid, rarely limoniform; colour in microscope often brown pale, occasionally yellow brown, rarely brown or yellow; guttules yes. papilla usually no, rarely yes or weak; Spore Code: O1 O2; P0 P1 (P2); D3 D4.

  Basidia: 26–44 (48) x 5–8 (9) μm; ave. Q 4.1–5.3; spore arrangement 4 spored;

  Cheilocystidia: main shape usually clavate-lageniform or clavate-ventricose, often cylindrical, rarely filiform or utriform; special features observed often septa or short, occasionally median thickening, geniculate or rostrate, rarely branching; cheilocystidia ratios: A/M = 1.41–1.67; A/B = 0.90–1.17; B/M = 1.36–1.64.

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

  Ixocutis: epicutis thickness (measured from exsiccata) up to 165 μm; ixocutis hyphae width up to 7 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis often cylindrical or isodiametric, occasionally ellipsoid or thickly sausage-shaped up to 17 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 75 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma griseopruinatum's preferred habitat appears to be grassland or pastureland with calcareous, grassy soil. Where only one possible associate was recorded, the most commonly recorded associate was Helianthemum (81.8%) but Tuberaria (9.1%) and Cistus (9.1%) were also recorded. In these cases the most commonly recorded family was Cistaceae (100.0%). We have additional records where Quercus (14.3%), Pinus (7.1%) and Eucalyptus (7.1%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Cistaceae (100.0%), Fagaceae (14.3%), Pinaceae (7.1%) and Myrtaceae (7.1%) The growth habit of our collections was often scattered, occasionally gregarious and rarely caespitose.

  According to our current collections, the species is found only in Europe. On the continent, 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. temperate broadleaf & mixed forests (57.1%) and mediterranean forests, woodlands & scrub (35.7%), specifically including the ecoregions: Appenine deciduous montane forests (28.6%), Iberian sclerophyllous and semi-deciduous forests (28.6%) and Western European broadleaf forests (14.3%). From collector information, it appears collections have been found in the 4.4 Grassland – Temperate (25.0%), 14.2 Pastureland (25.0%), 1.4 Forest – Temperate (25.0%) and 5.11 Wetlands (inland) – Alpine wetlands (inc. temporary waters from snowmelt) (16.7%) 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, Italy and France), the Southeast (Italy), the North (England and Denmark) and the Centre (Germany). Specimens have been collected from 38.0°N to 55.7°N.

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma griseopruinatum is neither monophyletic nor supported by bootstrap in the five-locus analysis. Please refer to H. erumpens to which H. griseopruinatum is very closely related and from which it cannot always be distinguished based on DNA sequence data. In Eberhardt et al. (2009) H. griseopruinatum was referred to as Hebeloma sp. Record JVG991224 (HJB11610) is an example of a collection with H. erumpens morphology and host association, but two different ITS variants present, one of which is the ITS variant normally encountered in H. griseopruinatum.

• arrow_drop_downarrow_drop_upCommentary
  The combination of almost smooth to very weakly ornamented and rather to very dextrinoid spores, the hourglass (clavate-lageniform) shape of the cheilocystidia and the pruinose pileus all indicate H. sect. Theobromina. Hebeloma griseopruinatum can be macroscopically distinguished from other species of H. sect. Theobromina by means of its habitat with Cistaceae, the pruinose covering of the pileus, and the orange brown pileus colour and microscopically by the combination of relatively large (with high ave. Q value) and rather dextrinoid spores, together with the short clavate-lageniform shaped cheilocystidia with relatively small average apex of the cheilocystidium. The implications of the shared molecular features between H. erumpens and H. griseopruinatum were discussed in detail in Eberhardt et al. (2012). In short, it is impossible to tell based on current knowledge and with the small number of collections of H. griseopruinatum, whether the two species are indeed distinct, as suggested by their morphological differences and by their different host associations. It should be noted though, that the hosts of both taxa belong to the Cistaceae. It is perhaps also worth noting that following the first recorded collection of this taxon in England in 2002 we revisited that site numerous times between then and 2009 (when the Danish collection appeared), hoping to find it again and obtain a photograph. Despite many visits during each year we have never collected it again at that location.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

Image gallery