Hebeloma ambustiterranum (Photo: H. J. Beker)

Taxonomy

Types: MEXICO: Tlaxcala, La Malinche National Park (19.275°N, 97.9825°W, alt. approx. 2835 m a.s.l.) on burnt soil in coniferous, montane, subtropical woodland under Pinus montezumae and Pinus teocote, 8 Jul. 2017, H.J. Beker (Holotype. herbarium acc. no. TLXM 6155 (holotype), BR5020224874626V (isotype), HJB16802).

• arrow_drop_downarrow_drop_upEtymology
  From ambustus (Latin adj.) meaning scorched, terra (Latin n.) meaning soil and the Latin suffix -anum indicating position to indicate growing on scorched soil. In Mexico, the local people burn the ground in the pine forests to encourage the growth of this mushroom, which they regard as an excellent edible mushroom. The local people refer to it in Nahuatl as the xolete de ocoxal (or ocoxalnanacatl), the mushroom of the pine needles from Chamusquinero, meaning from burnt ground.

• arrow_drop_downarrow_drop_upDiagnosis
  The small ellipsoid, non-dextrinoid, almost smooth basidiospores (on average 8.0–10.2 × 5.6–6.5 μm) and at least 50 full length lamellae distinguish this species from all other known North American Hebeloma species and the ITS sequence differentiates this species from all other known species, worldwide.

Description

Description of Hebeloma ambustiterranum based on 33 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (12) 16–45 (52) mm diameter; shape occasionally broadly umbonate or umbonate, rarely applanate, convex or weakly umbonate; characters often remains of universal veil, rarely spotting; margin characters often smooth, occasionally involute, rarely overhanging pileus; viscosity tacky when moist; colour variation usually unicolour, rarely two color; colour at centre occasionally cream, ochraceous or yellowish brown, rarely honey, sepia, umber or brownish olive.

  Lamellae: attachment emarginate; maximum depth 2–7 mm; number of complete lamellae 50–74; presence of tears absent; white fimbriate edge often weak, occasionally present.

  Cortina presence: yes.

  Stipe: (23) 24–60 (75) x 3–8 (10) {median} x 3–8 (10) {basal} mm; stipe Q 3.3–10.0; base shape cylindrical; floccosity pruinose at apex, usually fibrillose; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior often hollow, occasionally stuffed; stipe flesh discolouring occasionally yes or very strongly, rarely weak or no; slenderness measure 3.7–17.4; smell occasionally odourless or raphanoid, rarely weakly raphanoid, cocoa, earthy or strongly raphanoid; taste Not recorded.

  Spore deposit colour: clay-buff.

  Exsiccata characters: Not recorded.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape ellipsoid or ovoid; colour in microscope brown pale, very pale or yellow pale; guttules often yes, occasionally weak. papilla no; Spore Code: O1; P0; D1.

  Basidia: (24) 25–34 (36) x 6–8 (9) μm; ave. Q 3.7–4.4; spore arrangement 4 spored;

  Cheilocystidia: main shape lageniform or ventricose; special features observed often septa, occasionally yellow contents, rarely geniculate or median thickening; cheilocystidia ratios: A/M = 0.96–1.15; A/B = 0.51–0.70; B/M = 1.55–2.31.

  Pleurocystidia: none seen.

  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 cylindrical, occasionally ellipsoid up to 14 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 140 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma ambustiterranum's preferred habitat appears to be coniferous, montane, subtropical woodland or montane, subtropical woodland with soil, burnt soil or burnt soil and litter. Where only one possible associate was recorded, the most commonly recorded associate was Pinus (95.5%) but Quercus (4.5%) were also recorded. In these cases the most commonly recorded family was Pinaceae (95.5%). We have additional records where Alnus was recorded as a possible associate, but for these collections a number of possible associates were mentioned. Overall the most commonly recorded families are Pinaceae (96.0%) and Fagaceae (12.0%) The growth habit of our collections was often scattered, occasionally solitary or caespitose and rarely gregarious.

  According to our current collections, the species is found only in Northern America. 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. tropical & subtropical coniferous forests (78.1%) and deserts & xeric shrublands (12.5%), specifically including the ecoregions: Trans-Mexican Volcanic Belt pine-oak forests (78.1%). From collector information, it appears collections have been found only in the 1.9 Forest – Subtropical/tropical moist montane 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 Northern America all our records are from Mexico (Mexico).

• arrow_drop_downarrow_drop_upCommentary
  With its small ellipsoid, non-dextrinoid basidiospores and cheilocystidia swollen in the lower half, often lageniform or ventricose, this taxon clearly belongs to Hebeloma sect. Hebeloma and is closely related to the complex of species around H. mesophaeum. The close, but not crowded, lamellae with more than 50 full length lamellae rules out H. excedens and H. mesophaeum, both of which are widespread throughout North America (Eberhardt et al. 2022a). Indeed, were this mushroom collected in Europe, and the key of Beker et al. (2016) applied, this would key out to H. subtortum. Hebeloma subtortum is most common in southern Europe, growing with lowland pines, and not known from North America. Within North America, no known taxon in H. sect. Hebeloma with such small ellipsoid spores has this number of full-length lamellae, making these characters sufficient for its determination. Fig. 6D–E (Eberhardt et al. 2022) show this mushroom for sale in local markets of Tlaxcala, where it is regarded as a prized edible mushroom known as hongo de ocote (ocote mushroom) in Spanish (Montoya et al. 2002). It is gathered from the temperate pine woodlands at altitudes of 2000 m and above. The local people burn the ground in the pine forests, ahead of the growing season, to encourage the growth of this mushroom. Frequent, controlled fires prevent the development of hot fires that would also damage the pines and pine roots, which are required for the fungi to grow. It is referred to in Nahuatl by several names, for example as the Xolete de ocō-xāl or ocō-xālnanácatl (ocō-xālli = pine-litter; mushroom growing in ocō-xāl - the mushroom of the pine needles), rastrojo-nanácatl (mushroom growing on stubble), ocochalero, ocotero, ocoxal, ocochal, cholete de ocote, nixtamalero or as chamusquinero, meaning from burnt ground (Estrada-Martínez et al. 2009; Reyes-López et al. 2020; Viveros-Assad et al. 2019). It is likely the same species as mentioned by Guzmán (1977) as “joletes” in Spanish, described as commonly sold in the Amecameca market, where it is recommended to boil them and then discard the water so that they are safe for consumption.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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