Hebeloma rostratum (Photo: E. Campo)

Taxonomy

Types: ITALY: Friuli-Venezia Giulia, Pordenone, Sacile, Topaligo (45.5637°N, 12.2936°E, alt. approx. 25 m a.s.l.) under Populus sp., 10 Dec. 2006, E. Campo (Holotype. herbarium acc. no. TURA 177056 (holotype), BR BR-MYCO 174906-15 (isotype), HJB13086).

• arrow_drop_downarrow_drop_upEtymology
  From rostratus– meaning beaked to emphasise the occasionally rostrate cheilocystidia, a feature rarely seen in most European species of Hebeloma.

• arrow_drop_downarrow_drop_upDiagnosis
  Hebeloma rostratum clearly belongs to H. subsect. Echinospora based on spore characters, strong almost spiny ornamentation, constantly loosening perispore and very strongly dextrinoid, and cheilocystidium characters, primarily clavate-lageniform and more than 40 µm long. The cheilocystidium ave. apex width, at most 7.5 µm, is the smallest average apex width of all known species from this subsection.

Description

Description of Hebeloma rostratum based on 28 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (12) 16–34 (40) mm diameter; shape usually convex, occasionally broadly umbonate, rarely umbonate; characters rarely rimulose or spotting; margin characters often involute, occasionally smooth, crenulate or scalloped; viscosity tacky when moist; colour variation often two color, occasionally unicolour; colour at centre often yellowish brown, occasionally brick or dark fawn.

  Lamellae: attachment often emarginate, occasionally adnexed, rarely adnate or free; maximum depth 3–4 mm; number of complete lamellae 28–65; presence of tears often absent or visible with naked eye; white fimbriate edge often present, occasionally very strong.

  Cortina presence: no.

  Stipe: (17) 23–44 (55) x 2–6 (7) {median} x 2–6 (7) {basal} mm; stipe Q 4.3–25.0; base shape often cylindrical, occasionally tapering or clavate; floccosity occasionally floccose at apex, floccose, pruinose or pruinose at apex, rarely fibrillose; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior stuffed; stipe flesh discolouring often yes, occasionally no, rarely weak; slenderness measure 5.5–50.0; smell occasionally raphanoid, cocoa, odourless or weakly raphanoid, rarely earthy; taste often mild or raphanoid where recorded.

  Spore deposit colour: brownish olive.

  Exsiccata characters: occasionally dark, hard or pileus blackening.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid or limoniform; colour in microscope often brown, occasionally yellow brown; guttules often no, occasionally yes. papilla often very strongly, occasionally yes, rarely no; Spore Code: O3 O4; P2 P3; D3 D4.

  Basidia: (20) 24–43 (44) x 6–9 μm; ave. Q 3.5–4.8; spore arrangement 4 spored;

  Cheilocystidia: main shape clavate-lageniform or clavate-ventricose, occasionally clavate-stipitate, rarely lageniform, ventricose, cylindrical or lanceolate; special features observed often rostrate or septa, occasionally median thickening, bifurcate or apical thickening, rarely geniculate, clamped septa, large, many collapsed in exsiccata, mucronate, wavy or yellow contents; cheilocystidia ratios: A/M = 1.47–1.77; A/B = 0.89–1.29; B/M = 1.23–1.92.

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

  Ixocutis: epicutis thickness (measured from exsiccata) up to 100 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation yes; shape of trama elements beneath subcutis often thickly sausage-shaped, occasionally cylindrical, ellipsoid or oblong up to 35 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 120 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma rostratum's preferred substrate appears to be grassy soil or boggy soil. Where only one possible associate was recorded, the most commonly recorded associate was Populus (66.7%) but Quercus (11.1%), Salix (11.1%) and Tilia (11.1%) were also recorded. In these cases the most commonly recorded families were Salicaceae (79.0%), Fagaceae (10.5%) and Malvaceae (10.5%). We have additional records where Corylus (4.3%), Pinus (4.3%), Arbutus (4.3%) and Betula (4.3%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Salicaceae (82.6%), Fagaceae (17.4%), Betulaceae (8.7%) and Malvaceae (8.7%) The growth habit of our collections was often gregarious, occasionally scattered or solitary and rarely caespitose or connate.

  According to our current collections, the species is predominantly found in Europe (96.4%) but also found in Australasia (3.6%). 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. temperate broadleaf & mixed forests (66.7%) and mediterranean forests, woodlands & scrub (28.6%), specifically including the ecoregions: European Atlantic mixed forests (19.0%) and Po Basin mixed forests (19.0%). From collector information, it appears collections have been found in the 1.4 Forest – Temperate (42.1%), 14.5 Urban Areas (31.6%) and 14.3 Plantations (15.8%) 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 Europe we have records from the Southeast (Italy, Malta and Greece), the Centre (Germany and Belgium), the Southwest (France, Portugal, Italy and Spain) and the North (Denmark, Isle Of Man and Norway). Specimens have been collected from 35.9°N to 59.2°N.

  Within Australasia all our records are from New Zealand (New Zealand).

• arrow_drop_downarrow_drop_upMolecular results
  The sequences of Hebeloma rostratum form well supported monophyla in all single locus results and in the results of five and six locus analyses. The species can be identified with any of the tested loci. BLAST searches suggest that three ITS sequences (from environmental samples, HG937625 from Serbia, with Populus alba; UDB008849 Estonia, with P. balsamifera and UDB008817 Estonia, with P. alba) might also belong to H. rostratum, which extends the distribution to the east. There are no sequences published from outside Europe that are likely to be H. rostratum.

• arrow_drop_downarrow_drop_upCommentary
  The spores with strongly warty, almost spiny, ornamentation, constantly loosening perispore and very strongly dextrinoid, together with the shape of the cheilocystidia, firmly put this taxon in H. subsect. Echinospora. It is distinguished from other members of this subsection by the average size of the apex of the cheilocystidium, less than 7.5 μm. From our database records, Hebeloma rostratum is the most common member of this subsection of H. sect. Denudata. In many ways Alnicola clavuligeroides (P.D. Orton) Courtec. is microscopically similar to Hebeloma rostratum, but is without clamp connections. We did examine the holotype of this Alnicola sp., thinking it might be a Hebeloma, but on examination (molecularly as well as morphologically) we believe this to be an Alnicola, closely related to Alnicola bohemica (Velen.) Kühner.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

Image gallery