Hebeloma aanenii (Photo: H. J. Beker)

Taxonomy

Types: POLAND: Bialowieza National Park (Bialowieski Park Narodowy) (52.7211°N, 23.9056°E, alt. approx. 165 m a.s.l.) on acidic soil in mixed woodland pathside under Carpinus betulus, Picea abies, Populus sp. and Quercus sp., 19 Sep. 2008, H.J. Beker, I. Kałucka (Holotype. herbarium acc. no. BR BR-MYCO 173987-66 (holotype), C C-F- 90147 (isotype), HJB12630).

• arrow_drop_downarrow_drop_upEtymology
  In honour of Duur Aanen to whom we are deeply indebted for carrying out extensive research on biological mating between Hebeloma spp. as well as molecular analysis.

• arrow_drop_downarrow_drop_upDiagnosis
  Hebeloma aanenii has the typical cystidia of H. subsect. Denudata [H. subsect. Crustuliniformia]. It differs from H. alpinum, H. crustuliniforme, H. eburneum by the average size of its spores (length < 11 μm and width < 6 μm) and normally from H. geminatum by the average width of the cheilocystidium apex which is always < 9 μm and usually < 8 μm and from the rest of the species of its subsection by the average number of lamellae, which is always ≥ 60. It can be differentiated from H. geminatum based on sequence comparison of the partial RPB2 sequences and usually also the internal transcribed spacer of the nuclear ribosomal genes.

Description

Description of Hebeloma aanenii based on 144 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (17) 23–104 (170) mm diameter; shape often convex, occasionally umbonate, rarely broadly umbonate or strongly umbonate; characters rarely spotting; margin characters often smooth, occasionally involute, rarely crenulate, scalloped, sulcate, flexuous or serrate; viscosity tacky when moist; colour variation often unicolour, occasionally two color; colour at centre occasionally warm buff, cream or pale yellow, rarely pale cream, yellowish brown, dark pinkish buff, clay-red or honey.

  Lamellae: attachment usually emarginate, rarely adnate; maximum depth 2–9 mm; number of complete lamellae 59–110; presence of tears usually visible with naked eye, rarely absent or visible with x10 lens; white fimbriate edge often present, occasionally very strong.

  Cortina presence: no.

  Stipe: (22) 30–87 (130) x (3) 5–13 (18) {median} x (3) 5–16 (20) {basal} mm; stipe Q 2.1–15.0; base shape often clavate or cylindrical, occasionally bulbous, rarely subbulbous; floccosity often floccose, rarely weakly floccose, floccose at apex, pruinose, pruinose at apex or velute; rooting usually no, rarely weak; thick rhizoids at base usually absent, rarely present;

  Context: Texture firm; stipe interior often hollow, occasionally stuffed or superior wick, rarely basal wick; stipe flesh discolouring variable occasionally weak; slenderness measure 1.4–20.6; smell often raphanoid, rarely cocoa, odourless, strongly raphanoid, weakly raphanoid or fruit; taste often bitter, occasionally raphanoid, rarely weakly bitter, hot, mild or sweet where recorded.

  Spore deposit colour: often brownish olive, occasionally umber, rarely greyish brown.

  Exsiccata characters: occasionally pale, rarely fragile, pileus blackening or shiny.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, rarely fusoid, limoniform or ovoid; colour in microscope occasionally brown, yellow brown, brown yellow or yellow; guttules usually yes, occasionally no. papilla often no, occasionally weak, rarely yes; Spore Code: O2 O3; (P0) P1 (P2); D0 D1 (D2).

  Basidia: 21–36 (43) x 6–9 (10) μm; ave. Q 2.9–4.5; spore arrangement 4 spored;

  Cheilocystidia: main shape usually clavate-stipitate, often clavate-lageniform or clavate-ventricose, occasionally gently clavate, rarely capitate-stipitate, spathulate-stipitate, capitate, clavate or subcapitate; special features observed occasionally median thickening or apical thickening, rarely bifurcate, conglutinate, sinuate, thick content in neck, many collapsed in exsiccata, mucous, septa or wavy; cheilocystidia ratios: A/M = 1.58–2.49; A/B = 1.03–2.48; B/M = 0.85–1.60.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 400 μm; ixocutis hyphae width up to 7 μm; ixocutis hyphae encrustation usually yes, occasionally no; shape of trama elements beneath subcutis thickly sausage-shaped, often ellipsoid, occasionally cylindrical up to 20 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 85 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Where only one possible associate was recorded, the most commonly recorded associate was Salix (59.3%) but Betula (8.6%), Populus (7.4%), Quercus (7.4%), Fagus (3.7%), Corylus (3.7%), Picea (2.5%), Tilia (2.5%), Nothofagus (1.2%), Eucalyptus (1.2%), Helianthemum (1.2%) and Dryas (1.2%) were also recorded. In these cases the most commonly recorded families were Salicaceae (64.7%), Betulaceae (11.8%), Fagaceae (10.6%) and Pinaceae (5.9%). We have additional records where Pinus (13.8%), Larix (3.9%), Abies (3.1%), Alnus (2.3%), Carpinus (1.5%) and Pseudotsuga (1.5%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Salicaceae (66.9%), Betulaceae (26.1%), Pinaceae (26.1%) and Fagaceae (18.5%) The growth habit of our collections was often scattered, occasionally solitary and rarely caespitose or gregarious.

  According to our current collections, the species is predominantly found in Europe (87.1%) but also found in Northern America (5.7%), Temperate Asia (5.0%) and Australasia (2.1%). 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 (66.2%) and temperate conifer forests (14.4%), specifically including the ecoregions: Western European broadleaf forests (13.7%), Celtic broadleaf forests (10.8%) and Alps conifer and mixed forests (10.1%). 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 North (England, Norway, Denmark, Sweden and Scotland), the Centre (Germany, Netherlands, Belgium, Poland, Switzerland, Czech Republic and Slovakia), the Southwest (France and Spain) and the Southeast (Italy, North Macedonia and Kosovo). Specimens have been collected from 41.0°N to 66.5°N.

  Within Northern America we have records from Mexico (Mexico), Northwestern U.S.A. (Colorado and Washington), Subarctic America (Alaska) and Southwestern U.S.A. (California).

  Within Temperate Asia we have records from Caucasus (Georgia, Karachay-Balkar and Adygea) and Eastern Asia (Taiwan).

  Within Australasia we have records from New Zealand (New Zealand) and Australia (Victoria).

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma aanenii is monophyletic but unsupported in five-locus trees and in the six-locus tree. In spite of the rather large intraspecific ITS variation, it should in many cases be possible to recognize H. aanenii based on this locus. The combination of V6 and V9 also unambiguously identifies H. aanenii, though neither locus on its own suffices. Single copy nuclear genes might be less well suited for species identification.

• arrow_drop_downarrow_drop_upCommentary
  Given the shape of its cheilocystidia, Hebeloma aanenii clearly belongs to H. subsect. Crustuliniformia. The species most likely corresponds to ICG2 of Aanen & Kuyper (1999). Hebeloma aanenii is a constituent of the crustuliniforme-complex. It is likely that many collections of this species have been recorded under the name H. crustuliniforme and exist worldwide in herbaria under this name. It is closely related to H. crustuliniforme, H. eburneum, H. alpinum and H. geminatum. But its spores, normally less than 11 µm long and less than 6 µm wide distinguish it from the first three species. It can be distinguished from other members of this subsection by the number of complete lamellae, which is always at least 60. Until now, we have found no consistent morphological character to separate H. aanenii and H. geminatum. However, we can often separate these two taxa through the use of a mixture of characters, al- though none appears foolproof. The cheilocystidium average apex width for H. aanenii is usually smaller than that for H. geminatum. From our records, if the average width of the apex of the cheilocystidium is less than 8 μm then the collection is almost certainly H. aanenii. However, the average apex width can reach 9 μm and widths in this interval between 8 μm and 9 μm can be from either taxon. We have collections of Hebeloma aanenii from alpine habitats, where its size and the number of complete lamellae makes it distinctive by comparison with other Hebeloma spp. of this subsection, found in this habitat, apart from H. geminatum for which we also have collections from this habitat.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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