Hebeloma parvicystidiatum (Photo: J. Vesterholt)

Taxonomy

Types: ITALY: Tuscany, Cala Violina NW of Grosseto (approx. 42.83°N, 10.77°E, alt. approx. 15 m a.s.l.) in deciduous woodland under Quercus cerris, Quercus ilex and Quercus suber, 9 Nov. 2006, J. Vesterholt (06-1090) (Holotype. herbarium acc. no. C C-F-89925 (holotype), BR BR-MYCO 169127-56 (isotype), HJB11859).

• arrow_drop_downarrow_drop_upEtymology
  From parvus– small, and cystidiatus– with cystidia, emphasising the small cheilocystidia.

• arrow_drop_downarrow_drop_upDiagnosis
  Basidiomes usually in scattered groups but sometimes solitary. Pileus up to 50 mm in diam., convex or plano-convex; surface dry or slightly viscid, sometimes with remains of soil and leaves stuck to the pileus, neither hygrophanous nor striate, with a pruinose layer clearly visible on young fruit bodies; pruina grey or pale grey, often patchy, in some basidiomes dense and extensive, in others more limited; cuticle colour cinnamon, yellowish brown or ochraceous in the centre but paler towards the margin which is usually cream to pinkish buff and often with a clear delimitation (zonation) between the darker centre and the paler margin, which can be rather thin; pileus margin straight or scalloped, slightly involute even in fully grown basidiomes. Lamellae emarginate, moderately dense (L=54–65); colour cream, alutaceous or brown when young, later tabacine following spore maturity; edge fimbriate, paler than gill surface; lamellules abundant. Stipe central, cylindrical or tapering towards the base, up to 60 × 5–12 mm and between 4 and 7 mm at the base; white or alutaceous, sometimes discolouring brown with age or handling; surface dry, some scattered squamules, concolorous with the surface, making it appear floccose; interior stuffed or hollow sometimes with a superior wick. Cortina not observed. Flesh cream or pale brown. Smell may have slight raphanoid component but also often recorded as no smell or slightly fruity or earthy. Spores amygdaloid, with small apiculus and rounded at the end opposite the apiculus, with a distinct thinning of the spore wall and sometimes with a distinct papilla, guttulate with one or more oily drops, weakly to distinctly ornamented, visible without immersion but not conspicuous, with no loosening perispore or just a hint of loosening in a few spores and most spores very strongly dextrinoid (O2/3; P0/1; D3/4); spore colour under the microscope from yellow to yellow brown; spore size based on n=66 spores of the holotype, 5 % to 95 % percentile range 8.8–10.5 × 4.8–5.7 μm, with median 9.6 × 5.3 μm and avg. 9.7 × 5.3 μm with S. D. length 0.52 μm and width 0.28 μm, Q value 5 % to 95 % percentile range 1.58–2.05, with median 1.84 and avg. 1.83 with S. D. 0.13; spore size based on six collections medians 8.8–10.0 × 5.3–5.8 μm and avg. 8.8–10.0 × 5.3–5.7 μm with S. D. length 0.47–0.62 μm and width 0.22–0.36 μm, avg. Q 1.65–1.83. Basidia cylindrical to clavate and 4-spored, 19–34 × 7.0–9.6 μm, with avg. 23–31 × 7.7–8.4 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 3.7–6.1 μm, with median 4.9 μm and avg. 4.8 μm with S.D. 0.73 μm; across six collections median 4.9–6.2 μm and avg. 4.8–6.2 μm; with n=20–30 selected cheilocystidia of six collections the 5 % to 95 % percentile ranges are 23–45 × 3.3–7.9 × 2.7–5.1 × 4.4–8.3 μm while the averages are 30–34 × 4.8–6.2 × 3.3–4.2 × 5.3–6.7 μm and 31 × 4.8 × 3.5 × 6.2 μm avg. for the holotype. The avg. cheilocystidia ratios for the three collections were: A/M=1.26–1.68; A/B=0.77–1.22; B/M=1.41–2.08. Caulocystidia resemble cheilocystidia but tend to be larger, up to 75 μm long and 8 μm wide at the apex. Pileipellis is an ixocutis with a medium thick epicutis up to 100 μm, embedded hyphae up to 5.5 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 13 μm broad. Clamp connections present throughout the fruitbody.

Description

Description of Hebeloma parvicystidiatum based on 15 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (17) 25–38 (50) mm diameter; shape often convex, occasionally broadly umbonate, rarely strongly umbonate; characters occasionally hygrophanous or pruinose; margin characters occasionally involute, smooth, crenulate, overhanging pileus or scalloped; viscosity tacky when moist; colour variation often two color, occasionally unicolour; colour at centre often cinnamon, occasionally yellowish brown, rarely ochraceous.

  Lamellae: attachment usually emarginate, occasionally adnexed; maximum depth 4–5 mm; number of complete lamellae 54–65; presence of tears usually absent, rarely visible with x10 lens; white fimbriate edge occasionally absent, weak or present.

  Cortina presence: no.

  Stipe: (21) 24–53 (60) x 5–8 (12) {median} x 4–6 (9) {basal} mm; stipe Q 3.8–9.3; base shape cylindrical, occasionally tapering, rarely clavate; floccosity occasionally velute, pruinose at apex, floccose or pruinose, rarely weakly floccose; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior usually stuffed, occasionally hollow or superior wick; stipe flesh discolouring often no, rarely yes or weak; slenderness measure 2.8–14.0; smell often raphanoid, rarely earthy, odourless, fruit or weakly raphanoid; taste often weakly bitter or raphanoid where recorded.

  Spore deposit colour: brownish olive.

  Exsiccata characters: occasionally rich brown color.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid; colour in microscope often yellow brown, rarely brown or yellow; guttules yes. papilla often no, occasionally weak, rarely yes; Spore Code: O2 O3; P0 P1; D3 D4.

  Basidia: (18) 20–33 (34) x 6–9 μm; ave. Q 3.0–4.2; spore arrangement 4 spored;

  Cheilocystidia: main shape clavate-lageniform or clavate-ventricose, occasionally lageniform, ventricose or cylindrical; special features observed often septa or short, occasionally apical thickening or median thickening, rarely clamped septa; cheilocystidia ratios: A/M = 1.26–1.68; A/B = 0.77–1.22; B/M = 1.41–2.08.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 160 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation yes; shape of trama elements beneath subcutis often cylindrical, ellipsoid or thickly sausage-shaped, occasionally isodiametric up to 15 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 parvicystidiatum's preferred habitat appears to be deciduous woodland with decomposed litter. Where only one possible associate was recorded, the most commonly recorded associate was Quercus (90.9%) but Cistus (9.1%) were also recorded. In these cases the most commonly recorded families were Fagaceae (90.9%) and Cistaceae (9.1%). We have additional records where Pinus was recorded as a possible associate, but for these collections a number of possible associates were mentioned. Overall the most commonly recorded families are Fagaceae (92.9%), Cistaceae (21.4%) and Pinaceae (7.1%) The growth habit of our collections was often scattered, occasionally gregarious and rarely solitary.

  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. mediterranean forests, woodlands & scrub (64.3%) and temperate broadleaf & mixed forests (28.6%), specifically including the ecoregions: Appenine deciduous montane forests (21.4%), Northwest Iberian montane forests (21.4%) and Italian sclerophyllous and semi-deciduous forests (14.3%). From collector information, it appears collections have been found only in the 1.4 Forest – Temperate 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 Europe we have records from the Southwest (Spain, France and Italy) and the Southeast (Italy). Specimens have been collected from 38.1°N to 43.6°N.

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma parvicystidiatum is molecularly distinct and can be identified by any of the loci tested (Eberhardt et al. 2013). The closest phylogenetic relatives of this taxon appear to be H. plesiocistum and H. alboerumpens.

• arrow_drop_downarrow_drop_upCommentary
  The combination of distinctly ornamented and very dextrinoid spores together with the short hourglass (clavate-lageniform) shape of the cheilocystidia and the pruinose pileus all indicate H. sect. Theobromina. Hebeloma parvicystidiatum can usually be macroscopically distinguished from other species of H. sect. Theobromina by means of its pileus colour with more or less cinnamon centre and paler margin, although we have had collections that macroscopically resemble H. vesterholtii. Microscopically, the combination of very strongly dextrinoid and distinctly ornamented spores with hardly loosening perispore distinguish this species from other species of H. sect. Theobromina.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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