Hebeloma luteicystidiatum (Photo: J. Volders)

Taxonomy

Types: BELGIUM: Limburg, Houthalen (51.0155°N, 5.3519°E, alt. approx. 45 m a.s.l.) on boggy soil in deciduous willow thicket under Salix sp., 22 Oct. 2006, J. Volders (Holotype. herbarium acc. no. BR MYCO 166233-72 (holotype), C C-F-90150 (isotype), HJB11837).

• arrow_drop_downarrow_drop_upEtymology
  From luteus– yellow and cystidiatus– having cystidia, to emphasise the thick apical wall that sometimes looks yellow under the microscope.

• arrow_drop_downarrow_drop_upDiagnosis
  Based on its cheilocystidium shape, Hebeloma luteicystidiatum is a member of H. subsect. Denudata [H. subsect. Crustuliniformia]. The most distinctive and constant character of the species are the thick walls of the cheilocystidium apices. With its small stature and two-coloured pileus, H. luteicystidiatum is similar to H. pusillum. From the latter it can be separated based on the pileus colour, which may be dark, but not dark brick, and the cystidia of H. pusillum do not have cheilocystidia with wall thickening at the apex. Macroscopically, Hebeloma helodes is similar in terms of colouration, but is larger, has more crowded lamellae and shorter spores.

Description

Description of Hebeloma luteicystidiatum based on 12 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (6) 8–12 (15) mm diameter; shape convex; characters Not recorded; margin characters often involute or smooth; viscosity tacky when moist; colour variation two color; colour at centre honey.

  Lamellae: attachment often emarginate, occasionally adnate; maximum depth up to 2 mm; number of complete lamellae 21–28; presence of tears often visible with x10 lens or visible with naked eye; white fimbriate edge occasionally present, very strong or weak.

  Cortina presence: no.

  Stipe: (12) 17–30 x 1–2 {median} x 1–2 {basal} mm; stipe Q 12.0–20.0; base shape cylindrical, occasionally clavate; floccosity pruinose, occasionally floccose; rooting no; thick rhizoids at base absent;

  Context: Texture firm; stipe interior stuffed; stipe flesh discolouring yes; slenderness measure 19.8–65.0; smell often weakly raphanoid, occasionally odourless or raphanoid; taste bitter where recorded.

  Spore deposit colour: Not recorded.

  Exsiccata characters: often pileus blackening or stipe blackening, occasionally dark or lamellae blackening.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape amygdaloid, occasionally fusoid; colour in microscope often brown, occasionally yellow brown or yellow; guttules often no, occasionally yes. papilla often no, occasionally yes; Spore Code: (O1) O2; P0 P1 (P2); (D0) D1 D2.

  Basidia: 25–38 x 6–9 (10) μm; ave. Q 3.3–4.7; spore arrangement 4 spored;

  Cheilocystidia: main shape usually clavate-stipitate, often capitate-stipitate or spathulate-stipitate, occasionally capitate, clavate-lageniform or clavate-ventricose or subcapitate; special features observed often apical thickening, occasionally median thickening, septa or many collapsed in exsiccata; cheilocystidia ratios: A/M = 2.27–2.77; A/B = 2.21–2.68; B/M = 0.98–1.22.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 60 μm; ixocutis hyphae width up to 5 μm; ixocutis hyphae encrustation yes; shape of trama elements beneath subcutis ellipsoid or thickly sausage-shaped, occasionally angular or circular up to 20 μm wide.

  Caulocystidia: Similar to cheilocystidia but larger, up to 90 μm.

• arrow_drop_downarrow_drop_upSpore measurements

• arrow_drop_downarrow_drop_upCheilocystidia measurements

• arrow_drop_downarrow_drop_upHabitat and distribution
  Hebeloma luteicystidiatum's preferred habitat appears to be deciduous willow thicket or mixed woodland with boggy soil or boggy, clayey, sandy soil. Where only one possible associate was recorded, the most commonly recorded associate was Salix (85.7%) but Betula (14.3%) were also recorded. In these cases the most commonly recorded families were Salicaceae (85.7%) and Betulaceae (14.3%). We have additional records where Alnus (36.4%), Populus (27.3%) and Picea (27.3%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Salicaceae (90.9%), Betulaceae (45.5%) and Pinaceae (27.3%) The growth habit of our collections was occasionally gregarious or scattered and rarely connate or solitary.

  According to our current collections, the species is predominantly found in Europe (81.8%) but also found in Northern America (18.2%). 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 (75.0%) and boreal forests/taiga (16.7%), specifically including the ecoregions: European Atlantic mixed forests (41.7%), Western European broadleaf forests (25.0%) and Muskwa-Slave Lake taiga (16.7%). From collector information, it appears collections have been found in the 1.4 Forest – Temperate (62.5%) and 5.3 Wetlands (inland) – Shrub dominated wetlands (37.5%) IUCN habitats 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 Southwest (France and Spain), the Centre (Belgium and Netherlands) and the Southeast (Italy). Specimens have been collected from 42.4°N to 52.2°N.

  Within Northern America all our records are from Subarctic America (Northwest Territories).

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma luteicystidiatum is molecularly distinct and its clade receives high bootstrap support in all loci apart from Tef1a for which only a single sequence could be obtained. The ITS appears to be suitable for species identification of H. luteicystidiatum. We are not aware of any sequences from outside Europe that are likely to represent this taxon.

• arrow_drop_downarrow_drop_upCommentary
  Given the shape of its cheilocystidia, Hebeloma luteicystidiatum clearly belongs to H. subsect. Crustuliniformia. The species most likely corresponds to ICG6 of Aanen & Kuyper (1999). The thick apex of the cheilocystidium wall occurs quite frequently and is sometimes so thick it appears yellow through the microscope. The small stature of the basidiomes, the small number of lamellae, less than 30, the spore length, greater than 11.5 μm, and this apical thickening of the cheilocystidium allow this species to be quite easy to determine. In the past, it may have been confused with H. pusillum, which is also a very small Hebeloma occurring in wet boggy Salix thickets, but this latter taxon usually has more fusoid spores (higher spore Q) and does not exhibit the same thickening of the apex of the cheilocystidium wall. Given that we only have four recorded collections of H. luteicystidiatum, we suspect that it is more widely distributed than North West Europe, but we must await more collections in order to understand both the species delimitation and the distribution of this taxon better.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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