Hebeloma alboerumpens (Photo: J. Vila)

Taxonomy

Types: SPAIN: Girona, el Port de la Selva, sa Perafita (approx. 42.299°N, 3.233°E, alt. approx. 245 m a.s.l.) on soil in Mediterranean maquis under Cistus monspeliensis, 8 Jan. 2008, J. Vila, X. Llimona (Holotype. herbarium acc. no. LIP JVG1080108-19, BR BR-MYCO 169129-58, HJB1000145).

• arrow_drop_downarrow_drop_upEtymology
  From albus– pale and erumpens, the present participle of erumpere– to erupt (‘erupting’) to remind of the similarities and differences compared to Hebeloma erumpens, occurring in similar habitats.

• arrow_drop_downarrow_drop_upDiagnosis
  Basidiomes usually in groups, epigeous or slightly buried. Pileus up to 60 mm in diam., convex when young, later applanate or (sub)undulated; surface dry or slightly viscid, often with remains of soil and leaves stuck to the pileus, neither hygrophanous nor striate, with a finely and abundant pruinose layer; pruina white or whitish–grey, often patchy; cuticle colour pale brown or ochraceous brown; pileus margin straight, slightly revolute in fully grown basidiomes. Lamellae adnate to subdecurrent, moderately dense (L=60–64), thin, not ventricose; colour cream, alutaceous or brown when young, later tabacine following spore maturity; edge fimbriate, paler than gill surface; lamellules abundant. Stipe central, cylindric or with enlarged (subbulbose) base, shorter than the pileus diameter, up to 50 × 20 mm, white or alutaceous, rarely discolouring brown; surface dry, with fine fibrils and some scattered squamules, with pruinose apex, concolourous with the surface. Cortina not observed. Flesh thin, especially under the cap cuticle, cream or pale brown. Smell raphanoid. 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 no sign of loosening perispore and rather strongly dextrinoid (O1/2; P0; D3); spore colour under the microscope brown; spore size based on n=64 spores of the holotype, 5 % to 95 % percentile range 9.1–10.4 × 5.0–5.6 μm, with median 9.8 × 5.2 μm and avg. 9.7 × 5.2 μm with S. D. length 0.43 μm and width 0.19 μm, Q value 5 % to 95 % percentile range 1.70–2.01, with median 1.86 and avg. 1.86 with S. D. 0.1; spore size based on two collections holotype 5 % to 95 % percentile range 5.8–8.9 μm, with median 7.5 μm and avg. 7.4 μm with S.D. 1.08 μm; across two collections median 6.9–7.5 μm and avg. 7.1–7.4 μm; with n=23 selected cheilocystidia of two collections the 5 % to 95 % percentile ranges are 31–45 × 5.4–8.9 × 3.6–5.4 × 5.1–7.8 μm while the averages are 37–38 × 7.1–7.4 × 4.4–4.6 × 6.2–6.3 and 38 × 7.4 × 4.6 × 6.2 μm avg. for the holotype. The avg. cheilocystidia ratios for the two collections were: A/M=1.76–1.82; A/B=1.22–1.35; B/M=1.36–1.46. Caulocystidia resemble cheilocystidia but tend to be larger, up to 90 μm long and 10 μm wide at the apex. Pileipellis is an ixocutis with a relatively thin epicutis up to a maximum of 80 μm, embedded hyphae 2–4 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 fruit body.

Description

Description of Hebeloma alboerumpens based on 5 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (30) 45–59 (60) mm diameter; shape often convex, occasionally broadly umbonate or strongly umbonate; characters pruinose; margin characters often involute or smooth, occasionally reflexed; viscosity tacky when moist; colour variation unicolour; colour at centre occasionally clay-buff, ochraceous, orange-brown or dark pinkish buff.

  Lamellae: attachment often adnate, occasionally adnexed or emarginate; maximum depth up to 6 mm; number of complete lamellae 60–72; presence of tears often absent or visible with x10 lens; white fimbriate edge present.

  Cortina presence: no.

  Stipe: (30) 41–56 (63) x (8) 13–15 (18) {median} x (10) 13–19 (20) {basal} mm; stipe Q 3.1–4.3; base shape cylindrical, often clavate, occasionally subbulbous; floccosity often pruinose at apex, occasionally fibrillose, weakly floccose or pruinose; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior hollow or stuffed; stipe flesh discolouring no; slenderness measure 2.6–4.6; smell often raphanoid, occasionally weakly raphanoid; taste weakly bitter or raphanoid where recorded.

  Spore deposit colour: Not recorded.

  Exsiccata characters: Not recorded.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, occasionally ovoid; colour in microscope often yellow, occasionally brown or yellow brown; guttules yes. papilla no; Spore Code: O1 O2; P0; D3.

  Basidia: (21) 22–34 x 6–8 (9) μm; ave. Q 3.5–4.4; spore arrangement 4 spored;

  Cheilocystidia: main shape clavate-lageniform or clavate-ventricose, occasionally clavate, cylindrical, capitate or ventricose; special features observed often short or septa; cheilocystidia ratios: A/M = 1.49–1.82; A/B = 0.99–1.35; B/M = 1.36–1.54.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 180 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis often isodiametric or thickly sausage-shaped, occasionally cylindrical or ellipsoid up to 20 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 80 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma alboerumpens's preferred habitat appears to be Mediterranean maquis. Across our collections, Hebeloma alboerumpens has only been recorded as associating with Cistus (family Cistaceae). No growth habit has been recorded.

  According to our current collections, the species is found only in Europe. On the continent, collections have been found only in the mediterranean forests, woodlands & scrub WWF biome 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. (Northeast Spain and Southern France Mediterranean forests (40.0%), Tyrrhenian-Adriatic sclerophyllous and mixed forests (40.0%) and Iberian sclerophyllous and semi-deciduous forests (20.0%) ecoregions). From collector information, it appears collections have been found only in the 3.8 Shrubland – Mediterranean-type shrubby vegetation 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) and the Southeast (Italy). Specimens have been collected from 39.6°N to 42.3°N.

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma alboerumpens is monophyletic, supported by bootstrap and can be recognized based on ITS sequence data as well as on any other locus that has been sequenced to date. The closest relatives of this species are H. parvicystidiatum and H. plesiocistum, of which only the latter is Cistus-associated.

• arrow_drop_downarrow_drop_upCommentary
  The combination of almost smooth to very weakly ornamented and rather dextrinoid spores, the short hourglass (clavate-lageniform) shape of the cheilocystidia and the pruinose pileus all indicate H. sect. Theobromina. Hebeloma alboerumpens can be macroscopically distinguished from other species of H. sect. Theobromina by means of its habitat with Cistus and its pileus colour, with the pale pruinose covering of the pileus. Microscopically, the combination of small, narrow and rather dextrinoid spores, together with the short clavate-lageniform shaped cystidia and the relatively large average apex of the cheilocystidium distinguish this species from other species of H. sect. Theobromina. In habit, it is very close to H. erumpens, which has a darker, more colourful, pileus. Additional collections are needed to investigate the intraspecific variation and species delimitation.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

Image gallery