Hebeloma pseudofragilipes (Photo: H. J. Beker)

Taxonomy

Types: ENGLAND: Derby, Chatsworth (53.2291°N, 1.6075°W, alt. approx. 315 m a.s.l.) on grassy soil in mixed parkland under Tilia sp., 28 Oct. 2004, C.A. Hobart, H.J. Beker, det: H.J. Beker (Holotype. herbarium acc. no. BR-MYCO 174911-20 (holotype), C-F-92309 (isotype), HJB10468).

• arrow_drop_downarrow_drop_upEtymology
  From Greek pseudo– resembling but not equalling and from –fragilipes (fragilis– brittle, fragile and pes– foot, to emphasise the fragile stipe).

• arrow_drop_downarrow_drop_upDiagnosis
  Hebeloma pseudofragilipes possesses the cheilocystidia typical of H. subsect. Clepsydroida. The pileus colour, yellowish in the centre, lacking brown or pink tinges, and pale at the margin and the relatively narrow spores (< 6.5 µm) distinguish this species and H. fragilipes from the other members of this subsection. The average cheilocystidium ratio A/B (width at apex: maximum width in the lower part of the cheilocystidium) usually at most 1.25 normally separates this taxon from the closely related H. fragilipes even if the spore dextrinoidity is weak (i.e. D2 or less). Hebeloma pseudofragilipes can reliably be identified most easily by its V6 sequence, which is consistently different from H. fragilipes and all other Hebeloma species described, of which the sequence for this locus is known.

Description

Description of Hebeloma pseudofragilipes based on 165 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (13) 19–49 (115) mm diameter; shape often convex, occasionally umbonate, rarely broadly umbonate, strongly umbonate or weakly umbonate; characters rarely spotting or hygrophanous; margin characters often smooth, rarely involute, crenulate, ribbed, reflexed, scalloped, serrate or sulcate; viscosity tacky when moist; colour variation often unicolour, occasionally two color; colour at centre occasionally pale yellow or cream, rarely honey, warm buff, buff-yellow, pale cream, pinkish buff or dark pinkish buff.

  Lamellae: attachment usually emarginate, rarely adnate or decurrent tooth; maximum depth 1–7 mm; number of complete lamellae 40–73; presence of tears occasionally visible with naked eye or absent, rarely visible with x10 lens; white fimbriate edge usually present, occasionally weak, rarely absent.

  Cortina presence: no.

  Stipe: (14) 27–68 (90) x 3–7 (11) {median} x 3–10 (13) {basal} mm; stipe Q 3.5–16.3; base shape often clavate or cylindrical, rarely bulbous or tapering; floccosity occasionally floccose, pruinose or velute, rarely floccose at apex, weakly floccose, pruinose at apex, fibrillose or none; rooting usually no, rarely yes; 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 rarely weak; slenderness measure 3.3–21.9; smell often raphanoid, rarely strongly raphanoid, weakly raphanoid, odourless, cocoa or fruit; taste occasionally bitter or raphanoid, rarely mild, none or hot where recorded.

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

  Exsiccata characters: rarely stipe blackening, pale or pileus blackening.

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

  Basidia: (21) 22–34 (37) x 6–9 μm; ave. Q 3.0–4.5; spore arrangement 4 spored;

  Cheilocystidia: main shape usually clavate-lageniform or clavate-ventricose, occasionally clavate-stipitate, rarely clavate, gently clavate, cylindrical, ventricose, capitate-stipitate or lageniform; special features observed often median thickening, rarely septa, apical thickening, branching, clamped septa, grotesque, many collapsed in exsiccata, papillate, rostrate or spathulate; cheilocystidia ratios: A/M = 1.40–1.93; A/B = 0.84–1.34; B/M = 1.30–2.03.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 250 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation variable; shape of trama elements beneath subcutis often thickly sausage-shaped, occasionally angular, isodiametric, oblong or thinly sausage-shaped, rarely cylindrical or spherical 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 pseudofragilipes's preferred habitat appears to be deciduous woodland with decomposed litter. Where only one possible associate was recorded, the most commonly recorded associate was Fagus (37.0%) but Quercus (13.7%), Tilia (9.6%), Populus (8.2%), Betula (8.2%), Corylus (6.8%), Pinus (4.1%), Castanea (4.1%), Eucalyptus (2.7%), Picea (1.4%), Salix (1.4%), Abies (1.4%) and Cedrus (1.4%) were also recorded. In these cases the most commonly recorded families were Fagaceae (55.7%), Betulaceae (12.7%), Pinaceae (10.1%), Malvaceae (8.9%) and Salicaceae (8.9%). We have additional records where Carpinus (5.5%) and Alnus (1.4%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Fagaceae (56.9%), Betulaceae (40.4%), Pinaceae (19.9%), Salicaceae (16.4%) and Malvaceae (11.0%) The growth habit of our collections was often scattered, occasionally solitary and rarely gregarious or caespitose.

  According to our current collections, the species is predominantly found in Europe (98.2%) but also found in Australasia (1.8%). On these continents, collections have been found only in the temperate broadleaf & mixed forests 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. (Celtic broadleaf forests (16.1%) and Western European broadleaf forests (15.5%) ecoregions). 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, Denmark, Norway, Scotland, Sweden, Finland and Isle Of Man), the Centre (Belgium, Germany, Poland, Czech Republic and Netherlands), the Southwest (France, Portugal, Spain, Italy and Andorra) and the Southeast (Italy and North Macedonia). Specimens have been collected from 32.7°N to 60.4°N.

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

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma pseudofragilipes is well delimited based on five and six-loci concatenated. Hebeloma pseudofragilipes is well delimited from H. fragilipes and all other species by the mitochondrial loci, RPB2 and Tef1a but not by ITS.See also H. fragilipes and H. ingratum.

• arrow_drop_downarrow_drop_upCommentary
  Given the shape of its cheilocystidia and its spores at most O3, P2, Hebeloma pseudofragilipes clearly belongs to H. sect. Denudata subsect. Clepsydroida. This species most likely corresponds to ICG13 of Aanen & Kuyper (2004). As explained above, no ICG number was assigned by Aanen & Kuyper (1999) as the related strain never formed dikarya; hence, Aanen and co-workers were reluctant to assume that it represented an independent ICG. It appears that in their studies they had only one collection of this taxon. The pileus colour, almost always without brown tones, often has a ‘poached egg’ appearance, slightly yellow or yellow-cream in the centre with a pale cream to white margin. The spores are usually distinctly to strongly dextrinoid and in the key we key it out in two places, with the strongly dextrinoid species of this subsection as well as with the indextrinoid to distinctly but not strongly dextrinoid group of species. The pileus colour, the relatively narrow spores (< 6.5 μm) and the relatively high spore Q distinguish this species and H. fragilipes from the other members of this subsection. It can be separated from H. fragilipes through consideration of the cheilocystidium averages: If A/B is less than 1.4 and A is at most 6.5 and B is greater than 5 then it is H. pseudofragilipes, and if any of these conditions fail then it is H. fragilipes, i.e. the apex of the cheilocystidium within H. pseudofragilipes is usually less swollen and the basal part of the cheilocystidium more swollen giving a smaller ratio between the two. For this species this ratio is rarely greater than 1.25 whereas for H. fragilipes it is always larger than 1.25. The decision in favour of molecular data as delimiting character as opposed to morphology was motivated by the greater distinctiveness of the sequence data. Eberhardt et al. (2016) also considered using the average A/B ratio of 1.25 as cut-off point for the species delimitation. However, in that case the average A/B values of H. fragilipes and H. pseudofragilipes would have formed a continuum. In addition, members of H. fragilipes would have been molecularly clearly heterogeneous and neither taxon would have been monophyletic. Of note in this context is the hypotheses of Aanen et al. (2004) who posited that mitochondria might have a decisive role in intercompatibility. We suspect that many herbarium records labelled as Hebeloma fragilipes should be referred to H. pseudofragilipes.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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