Hebeloma aestivale (Photo: J. Vesterholt)

Taxonomy

Types: DENMARK: E-Jylland, Arhus, Forstbotanisk Have UTM NH7420 TBU 21 (approx. 56.12°N, 10.2°E, alt. approx. 55 m a.s.l.) on calcareous, grassy soil in parkland grassland under Quercus sp., 10 Aug. 1993, J. Vesterholt (93-553) (Holotype. herbarium acc. no. C JV93-553, HJB1000035; Isotype. herbarium acc. no. C JV93-552, HJB1000119).

Homotypic synonyms:

• Hebeloma aestivale J.H. Petersen & Vesterh., Danske storsvampe (Basidiesvampe): 414 (1990)

• arrow_drop_downarrow_drop_upEtymology
  From aestivus– summer, to emphasise its appearance during August and hence it is an early basidiome-producing Hebeloma. Our collections from Northern Europe range from August to October while our collections from Southern Europe range from October to November.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  Pileus 17–58 mm diam. convexus vel expansus, saepe irregularis, sordide flavidofuscus vel sordide aurantioacofuscus, ad marginem versus pallidior, viscidus vel mucidus, demum siccus. Lamellae profunde emarginatae, satis distantes, ad margines albo-fimbriatae, guttulis nullis vel inter conditiones uvidas minutis. Stipes 19–65 x 4.5–13 mm magnus, cylindricus vel deorsum paulum attenuatus, albidus, floccosus, solidus vel fistulosus, ad basem plerumque funiculos myceliales albos conspicuis praebens. Cortina nulla. Velum non observatum. Odor manifestis sed exiguus, pulveris cacao raphanoide paulum affectus. Sapor subraphanoides vel subamarus. Sporeae amygdaloides, 11.5–14 x 6–7.5 μm magnae, reactione dextrinoide manifesta, ornamento manifesto, perisporio deciduo. Cheilocystidia cylindrica vel anguste clavata, 46–107 μm longa, apice plerumque 5.6–7.2 μm crassa, valde numerosa, conferta. Sub Fago et Quercu.

• arrow_drop_downarrow_drop_upEnglish translation
  English translation: Pileus 17–58 mm diam., convex then expanding, often irregular, yellow-brown or sordid orange-brown, paler towards margin, viscid to slimy, then dry. Lamellae deeply emarginate, rather distant, with white fimbriate margin, without guttules or with minute guttules in moist condition. Stipe 19–65 × 4.5–13 mm, cylindrical or towards base weakly attenuated, white, floccose, solid or fistulose, at base usually with conspicuous white mycelial strands. Cortina none. Velum absent. Smell distinct but weak, reminiscent of cacao with raphanoid component. Taste subraphanoid or slightly bitter. Spores amygdaloid, 11.5–14 × 6–7.5 μm, distinctly dextrinoid, with manifest ornamentation, with loosening perispore. Cheilocystidia cylindrical to narrowly clavate, 46–107 μm long, usually 5.6–7.2 μm wide at apex, very abundant, close together. Under Fagus and Quercus.

Description

Description of Hebeloma aestivale based on 74 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (17) 22–67 (85) mm diameter; shape occasionally convex, umbonate or broadly umbonate, rarely strongly umbonate or weakly umbonate; characters occasionally spotting, rarely remains of universal veil; margin characters usually smooth, occasionally involute, rarely sulcate, eroded or scalloped; viscosity tacky when moist; colour variation often two color, occasionally unicolour; colour at centre occasionally ochraceous or yellowish brown, rarely dark pinkish buff, cinnamon, umber, honey, clay-red, buff-yellow, orange-brown, clay-buff, cream or pinkish buff.

  Lamellae: attachment usually emarginate, rarely adnate, decurrent tooth, free or decurrent; maximum depth 2–10 mm; number of complete lamellae 35–60; presence of tears occasionally absent, visible with naked eye or visible with x10 lens; white fimbriate edge often present, occasionally weak, rarely absent or very strong.

  Cortina presence: no.

  Stipe: (19) 38–79 (95) x (3) 5–14 (21) {median} x 4–10 (20) {basal} mm; stipe Q 3.3–15.5; base shape often cylindrical, occasionally clavate or tapering, rarely bulbous; floccosity often floccose, occasionally pruinose, rarely weakly floccose, none, decorticating, floccose at apex, pruinose at apex or velute; rooting usually no, rarely yes; thick rhizoids at base often absent, occasionally present;

  Context: Texture firm; stipe interior usually hollow, occasionally superior wick or stuffed; stipe flesh discolouring variable occasionally weak; slenderness measure 3.0–29.3; smell often raphanoid, occasionally cocoa or odourless, rarely weakly raphanoid, strongly raphanoid or soap; taste often bitter, occasionally mild or raphanoid, rarely weakly raphanoid, strongly bitter or hot where recorded.

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

  Exsiccata characters: occasionally dark, rarely fragile or shiny.

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

  Basidia: (29) 30–46 (48) x 7–10 (11) μm; ave. Q 3.6–4.8; spore arrangement Not recorded;

  Cheilocystidia: main shape usually gently clavate, often clavate, occasionally cylindrical or clavate-lageniform or clavate-ventricose, rarely clavate-stipitate, lageniform, ventricose or tapering; special features observed occasionally clamped septa or septa, rarely apical thickening, bifurcate or many collapsed in exsiccata; cheilocystidia ratios: A/M = 1.27–1.61; A/B = 1.03–1.67; B/M = 0.92–1.34.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 300 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis often ellipsoid or thickly sausage-shaped, occasionally oblong or spherical up to 20 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 150 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma aestivale's preferred habitat appears to be deciduous woodland, mixed woodland or deciduous woodland lakeside pathside with decomposed litter or calcareous soil and litter. Where only one possible associate was recorded, the most commonly recorded associate was Fagus (50.0%) but Quercus (30.0%), Tilia (7.5%), Populus (2.5%), Betula (2.5%), Salix (2.5%), Corylus (2.5%) and Carpinus (2.5%) were also recorded. In these cases the most commonly recorded families were Fagaceae (79.5%), Betulaceae (9.1%) and Malvaceae (6.8%). We have additional records where Castanea (2.9%), Alnus (1.5%) and Pinus (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 Fagaceae (83.8%), Betulaceae (38.2%) and Malvaceae (7.3%) The growth habit of our collections was often scattered, occasionally solitary and rarely caespitose.

  According to our current collections, the species is found only in Europe. On the continent, 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. (European Atlantic mixed forests (30.4%), Western European broadleaf forests (24.6%), English Lowlands beech forests (20.3%) and Celtic broadleaf forests (10.1%) 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 Centre (Belgium, Germany and Switzerland), the North (England and Denmark), the Southwest (France, Channel Islands and Spain) and the Southeast (Italy). Specimens have been collected from 41.6°N to 56.9°N.

• arrow_drop_downarrow_drop_upMolecular results
  This species forms monophyletic clades and can be differentiated from all other taxa by all loci tested. Available data does not allow any final conclusions as to whether H. aestivale should be included in H. sect. Velutipes or has an isolated position within the genus. The ITS is well suited for the identification of this species. We have obtained the ITS1 of the type of H. aestivale, supporting our concept of the species. There is to date no published ITS sequence from outside Europe that is likely to belong to H. aestivale.

• arrow_drop_downarrow_drop_upCommentary
  Given the shape of its cheilocystidia, gently clavate, together with the spores rather strongly to strongly dextrinoid, Hebeloma aestivale clearly belongs to either H. sects. Sinapizantia or Velutipes. The number of full length lamellae distinguish this taxon from members of H. sect. Sinapizantia. With regard to H. sect. Velutipes, given that the majority of cheilocystidia are rather long and slender and not particularly swollen at the base (cheilocystidium ratio B/M is less than 1.35), H. aestivale could only be confused with H. incarnatulum, H. leucosarx or H. velutipes. Its spores mostly have a perispore strongly and constantly loosening (P2 or P3), which separates H. aestivale from these other species. The cheilocystidia are most like those of H. incarnatulum, but the spores of the latter are relatively weakly ornamented (O1–2) and with perispore at most slightly loosening in a few spores (P0–1). The slender, long and narrow cheilocystidia together with the strongly ornamented, strongly dextrinoid spores with strongly loosening perispore characterize this species and normally make it straightforward to determine microscopically. Macroscopically, the size and habitat, together with the usually indistinct or inconspicuous drops on the lamellae edges will probably rule out most members of H. sect. Denudata and also some members of H. sect. Velutipes such as H. velutipes. It might be confused with H. celatum, from which it can usually be separated in the field based on the number of full length lamellae (L), which for H. aestivale is usually less than 60, while for H. celatum it is usually greater than 60 (see also the discussion under H. celatum).

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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