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Taxonomy

Full name: Hebeloma vesterholtii Beker & U. Eberh., Mycol. Prog 9: 218 (2010)
Genus: Hebeloma
Section: Theobromina

Types: BELGIUM: Luxembourg, Han sur Lesse (50.1142°N, 5.1715°E, alt. approx. 155 m a.s.l.) on calcareous, grassy soil in deciduous woodland under Carpinus sp., Corylus sp., Fagus sp. and Quercus sp., 19 Sep. 2004, H.J. Beker (Holotype. herbarium acc. no. BR-MYCO 166528-76, HJB1000133).

  • arrow_drop_downarrow_drop_upEtymology
    In honour of Jan Vesterholt who has made a huge contribution to our understanding of the genus Hebeloma.
  • arrow_drop_downarrow_drop_upOriginal diagnosis
    Pileus usque ad 55 mm in diam., convexus vel obtuse umbonatus; superficies sicca vel leviter viscida, interdum hygrophana, haud striata, ochracea vel bruno ochracea, praeter marginem pallidum cum coloribus cremeis vel roseis. Lamellae adnatae vel emarginatae, parce densae, tenues; color saturate cremeus, alutaceus vel brunneoalutaceus pallidus vel brunneus, demum brunneo-olivaceus. Acies fimbriata. Stipes centralis, interdum attenuatus vel clavatus basin versus, usque ad 75 mm longus et 10 mm crassus, candidus vel alutaceus; superficies sicca, pruinosa vel floccosa. Cortina non visa. Caro cremea vel pallide brunnea; odor compositus (cacao et raphanoideus). Sporae amygdaloideae, fere laeves vel inconspicue ornamentatae, valde dextrinoideae; 7.8–9.5 x 4.7–5.6 μm. Basidia tetrasporica, 21–33 x 5.6–8.4 μm, cylindrica vel clavata. Pleurocystidia non visa. Cheilocystidia subclavata, in parte inferiori incrassata, apex 4.4–6.3 μm latus. Caulocystidia cheilocystidiiformia. Fibulae omnipraesentes.
  • arrow_drop_downarrow_drop_upEnglish translation
    Pileus up to 55 mm in diam., convex to bluntly umbonate; surface dry or slightly viscid, sometimes hygrophanous, not striate, ochre to brown-ochre, paler towards margin with cream to pinkish colour. Lamellae adnate to emarginate, moderately distant, thin, saturated cream-colour, yellowish to yellow-brown or pale brown, then brown-olivaceous with fimbriate edge. Stipe central, sometimes attenuate or clavate towards base, up to 75 mm long and 10 mm thick, white to yellowish; surface dry, pruinose to floccose. Cortina not seen. Context cream-colour to pale brown; smell composite (cocoa and raphanoid). Spores amygdaloid, sometimes smooth or indistinctly ornamented; strongly dextrinoid, 7.8–9.5 × 4.7–5.6 μm. Basidia four-spored, 21–33 × 5.6–8.4 μm, cylindrical or clavate. Pleurocystidia not seen. Cheilocystidia subclavate, widened in lower part, apex 4.4–6.3 μm wide. Caulocystidia similar to cheilocystidia. Clamp connections abundant in all tissues.

Description

  • arrow_drop_downarrow_drop_upThresholds
Description of Hebeloma vesterholtii based on 25 collections
  • arrow_drop_downarrow_drop_upMacroscopic description
    Pileus: (20) 25–50 (85) mm diameter; shape often convex, occasionally umbonate or broadly umbonate, rarely strongly umbonate or weakly umbonate; characters occasionally hygrophanous; margin characters often smooth, occasionally involute, rarely eroded or reflexed; viscosity tacky when moist; colour variation usually unicolour, rarely two color; colour at centre occasionally yellowish brown or cinnamon, rarely pinkish buff, ochraceous, brownish olive, dark pinkish buff, fawn, dark brick, clay-buff, umber or clay-pink.

    Lamellae: attachment usually emarginate, occasionally adnate; maximum depth 4–8 mm; number of complete lamellae 56–87; presence of tears usually absent, rarely visible with naked eye; white fimbriate edge often weak, occasionally present.

    Cortina presence: no.

    Stipe: (25) 35–67 (80) x 4–10 {median} x 4–10 {basal} mm; stipe Q 5.2–14.4; base shape often cylindrical, occasionally tapering, rarely bulbous or clavate; floccosity occasionally pruinose, pruinose at apex, floccose or weakly floccose, rarely fibrillose, none or velute; rooting no; thick rhizoids at base absent;

    Context: Texture firm; stipe interior usually hollow, occasionally stuffed or superior wick; stipe flesh discolouring often no, occasionally yes, rarely weak; slenderness measure 5.9–16.8; smell often raphanoid, occasionally odourless, rarely cocoa, strongly raphanoid, weakly raphanoid or sweet; taste usually mild, occasionally raphanoid, bitter or weakly bitter where recorded.

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

    Exsiccata characters: occasionally pileus blackening or dark, rarely lamellae blackening.

  • arrow_drop_downarrow_drop_upMicroscopic description
    Spores: shape amygdaloid; colour in microscope occasionally brown, very pale or yellow pale, rarely yellow; guttules yes. papilla usually no, rarely weak; Spore Code: (O1) O2; P0 (P1); D3 (D4).

    Basidia: 21–33 x 5–8 (10) μm; ave. Q 3.2–4.3; spore arrangement 4 spored;

    Cheilocystidia: main shape clavate-lageniform or clavate-ventricose, occasionally ventricose, cylindrical or lageniform, rarely gently clavate, clavate, filiform or capitate; special features observed often short or median thickening, occasionally geniculate or septa, rarely bifurcate, mucronate, irregular, rostrate, apical thickening or basal thickening; cheilocystidia ratios: A/M = 1.35–1.65; A/B = 0.84–1.24; B/M = 1.27–1.74.

    Pleurocystidia: none seen.

    Ixocutis: epicutis thickness (measured from exsiccata) up to 180 μm; ixocutis hyphae width up to 5 μm; ixocutis hyphae encrustation yes; shape of trama elements beneath subcutis isodiametric.

    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 vesterholtii's preferred habitat appears to be deciduous woodland. Where only one possible associate was recorded, the most commonly recorded associate was Quercus (71.4%) but Picea (28.6%) were also recorded. In these cases the most commonly recorded families were Fagaceae (75.0%) and Pinaceae (25.0%). We have additional records where Carpinus (33.3%), Fagus (33.3%), Corylus (16.7%), Castanea (12.5%), Pinus (12.5%), Cistus (4.2%) and Abies (4.2%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Fagaceae (83.3%), Betulaceae (33.3%) and Pinaceae (20.8%) The growth habit of our collections was often scattered, occasionally gregarious and rarely caespitose or 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. temperate broadleaf & mixed forests (62.5%) and mediterranean forests, woodlands & scrub (29.2%), specifically including the ecoregions: Western European broadleaf forests (29.2%). 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 Southeast (Italy, Bulgaria and Croatia), the Southwest (France, Spain and Italy), the Centre (Belgium and Germany) and the North (England and Denmark). Specimens have been collected from 39.5°N to 55.9°N.

  • arrow_drop_downarrow_drop_upMolecular results
    Molecular data place Hebeloma vesterholtii in H. sect. Theobromina. The species forms a monophyletic clade with excellent bootstrap support. The species is molecularly distinct in all loci tested apart from nucLSU (Eberhardt et al. 2013). The closest phylogenetic relatives of this taxon appear to be H. theobrominum, H. erumpens and H. griseopruinatum, of which only H. theobrominum appears to share hosts with H. vesterholtii.
  • arrow_drop_downarrow_drop_upCommentary
    The combination of almost smooth to very weakly ornamented and strongly dextrinoid spores brings to mind either H. sect. Velutipes or H. sect. Theobromina. The known species in H. sect. Velutipes tend to have more ornamented spores and/or differently shaped cystidia. Their cheilocystidia are generally much more gently clavate than those of H. vesterholtii. The very pale small spores and the shape of the cystidia strongly support the assignment of H. vesterholtii to H. sect. Theobromina. This taxon can be readily distinguished both morphologically and molecularly from the other members of this section. The narrow (at most 5.5 μm) and weakly ornamented spores as well as the habitat eliminate all possibilities except H. theobrominum. It is likely that previous collections have been confused with H. theobrominum, however, H. vesterholtii is distinguishable from the latter species by means of its differently shaped spores and different pileus colour. The pileus colour of H. theobrominum ranges from deep cinnamon to red-brown to dark brick as opposed to the lighter and often more yellowish to buff colours of H. vesterholtii. Further, the average spore Q of H. theobrominum is at least 1.8, while the average spore Q of H. vesterholtii is always less than 1.8. Based on our collections, there is no overlap in the average spore Q, though there is only a small gap between the two ranges. Thus a collection of either species with a misleading average spore Q cannot be ruled out. However, in cases where the average spore Q may give an ambiguous identification, the pileus colour should help distinguish between the two species.
Geographic distribution
Phenology
  • arrow_drop_downarrow_drop_upAdditional cited collections

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