Hebeloma naviculosporum (Photo: M. Meusers)

Taxonomy

Types: SPAIN: Guadalajara, Pelagallinas, between Condemios de Abajo and Aldeanueva de Atienza (41.1934°N, 3.0907°W, alt. approx. 1350 m a.s.l.) on mossy soil in coniferous woodland under Pinus sylvestris, 4 Oct. 1991, M. Heykoop, G. Moreno, det: M. Heykoop, G. Moreno, F. Esteve-Raventós (Holotype. herbarium acc. no. AH14256, HJB1000023; Isotype. herbarium acc. no. AH14256, HJB1000009).

• arrow_drop_downarrow_drop_upEtymology
  From naviculus– navicular and sporus– spored, to emphasise the navicular shape of the spores.

• arrow_drop_downarrow_drop_upOriginal diagnosis
  Pileus usque 3,5 cm diam., plano-convexus, ochraceo-aurantiacus sive fuscus, viscidus. Stipes usque 5,5 x 0,6 cm cylindraceus, albidus. Laminae emarginatae eius caro albida, colore fusco usque basim stipitis. Odore terroso cum scisso fit. Sporae 10–13,8(–14,5) x (4)4,5–5,1(5,5) μm, naviculares, confertim fusiformes, verrucosae, ochraceo-castaneo colore. Basidia tetrasporica, 27–40 x 6–7 μm. Pleurocystidia absentia. Pileipellis hyphis 2,5–5 μm diam., fibulatis constantia. Habitat: sub pino sylvestri, apud Sphagnum sp.

• arrow_drop_downarrow_drop_upEnglish translation
  Pileus up to 3.5 cm in diam., plano-convex, orange-ochraceous to brown, viscid. Stipe up to 5.5 × 0.6 cm, cylindrical, whitish. Lamellae emarginate, white like the context, at base of stipe brown. Smell earth-like when cut. Spores 10–13.8(–14.5) × (4)4.5–5.1(5.5) μm, navicular, narrowly fusiform, verrucose, reddish ochre. Basidia four-spored, 27–40 × 6–7 μm. Pleurocystidia absent. Pileipellis made up of 2.5–5 μm wide clamped hyphae. Habitat under Pinus sylvestris, among Sphagnum sp.

Description

Description of Hebeloma naviculosporum based on 13 collections

• arrow_drop_downarrow_drop_upMacroscopic description
  Pileus: (20) 22–49 (62) mm diameter; shape often umbonate, occasionally convex or broadly umbonate; characters occasionally hygrophanous or remains of universal veil; margin characters often smooth, occasionally crenulate or eroded; viscosity tacky when moist; colour variation usually unicolour, occasionally two color; colour at centre often orange-brown, occasionally yellowish brown.

  Lamellae: attachment usually emarginate, occasionally adnate; maximum depth 3–8 mm; number of complete lamellae 60–88; presence of tears often absent, occasionally visible with x10 lens; white fimbriate edge occasionally present, weak or absent, rarely very strong.

  Cortina presence: no.

  Stipe: (18) 26–67 (80) x 5–13 (15) {median} x 5–12 (14) {basal} mm; stipe Q 3.6–9.2; base shape often cylindrical or tapering, occasionally clavate; floccosity usually pruinose at apex, occasionally fibrillose, floccose or pruinose; rooting usually no, occasionally weak; thick rhizoids at base absent;

  Context: Texture firm; stipe interior often hollow or stuffed; stipe flesh discolouring often no, occasionally yes or weak; slenderness measure 2.7–16.8; smell occasionally cocoa, earthy, fruit, raphanoid or weakly raphanoid; taste often weakly bitter or mild where recorded.

  Spore deposit colour: occasionally ochraceous, brownish olive or umber.

  Exsiccata characters: Not recorded.

• arrow_drop_downarrow_drop_upMicroscopic description
  Spores: shape usually fusoid or navicular, occasionally amygdaloid; colour in microscope often yellow, occasionally brown yellow or yellow pale; guttules variable. papilla often no, occasionally weak, rarely yes; Spore Code: O2 O3; P1 P2; (D2) D3.

  Basidia: (23) 24–34 (35) x (4) 5–8 μm; ave. Q 3.7–5.1; spore arrangement 4 spored;

  Cheilocystidia: main shape cylindrical, occasionally clavate-lageniform or clavate-ventricose, gently clavate or clavate, rarely clavate-stipitate; special features observed occasionally short, clamped septa, irregular, septa or branching, rarely median thickening; cheilocystidia ratios: A/M = 1.07–1.41; A/B = 0.98–1.38; B/M = 0.85–1.17.

  Pleurocystidia: none seen.

  Ixocutis: epicutis thickness (measured from exsiccata) up to 100 μm; ixocutis hyphae width up to 6 μm; ixocutis hyphae encrustation often yes, occasionally no; shape of trama elements beneath subcutis often thickly sausage-shaped or ellipsoid, occasionally circular, cylindrical, ovate or thinly sausage-shaped up to 17 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 naviculosporum's preferred habitat appears to be lawn. Where only one possible associate was recorded, the most commonly recorded associate was Pinus (42.9%) but Picea (42.9%) and Salix (14.3%) were also recorded. In these cases the most commonly recorded families were Pinaceae (88.9%) and Salicaceae (11.1%). We have additional records where Alnus (9.1%) and Betula (9.1%) were recorded as possible associates, but in these cases a number of possible associates were mentioned. Overall the most commonly recorded families are Pinaceae (90.9%), Betulaceae (18.2%) and Salicaceae (18.2%) The growth habit of our collections was scattered and often caespitose.

  According to our current data, the species is found on multiple continents with collections found in Europe (76.9%) and Northern America (23.1%). 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 (46.2%), mediterranean forests, woodlands & scrub (23.1%), temperate conifer forests (15.4%) and boreal forests/taiga (15.4%), specifically including the ecoregions: Western European broadleaf forests (38.5%) and Iberian conifer forests (15.4%). From collector information, it appears collections have been found in the 14.5 Urban Areas (33.3%), 1.4 Forest – Temperate (33.3%), 4.4 Grassland – Temperate (11.1%), 5.11 Wetlands (inland) – Alpine wetlands (inc. temporary waters from snowmelt) (11.1%) and 1.1 Forest – Boreal (11.1%) 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 Centre (Germany, Switzerland and Slovakia) and the Southwest (Spain). Specimens have been collected from 41.2°N to 49.2°N.

  Within Northern America we have records from Eastern Canada (Newfoundland and Labrador), Northeastern U.S.A. (Pennsylvania) and Subarctic America (Nunavut).

• arrow_drop_downarrow_drop_upMolecular results
  Hebeloma naviculosporum is very well supported in the five-locus phylogeny. Also, all single locus apart from V9 support H. naviculosporum as a monophyletic species with or without bootstrap support ≥ 80%. The ITS of the type of H. naviculosporum has been amplified and is included in the H. naviculosporum clade in the ITS tree. We are not aware of any published ITS sequences from outside Europe that are likely to belong to this species, although there appears to be a close relative (in terms of ITS similarity) of H. naviculosporum and H. nanum in Alaska.

• arrow_drop_downarrow_drop_upCommentary
  Hebeloma naviculosporum is a very distinctive Hebeloma species, both macroscopically and microscopically. In the field, it is the colour of the pileus that is the most remarkable feature; an orange brown colour that appears to be confined, in Europe, to this species and the closely related H. catalaunicum and H. nanum. Microscopically, the navicular shaped spores with Q value greater than 2.1 are equally eye catching and not known from any other species with primarily cylindrically shaped cheilocystidia. (Hebeloma cylindrosporum also has spores with a high Q value, but here the spores are much shorter and distinctly cylindrically shaped.) These characters are sufficient to separate H. naviculosporum from all other European Hebeloma spp. The cheilocystidia of this species are more problematic; they are primarily cylindrically shaped, but a number can also appear gently clavate. If one focuses on the gently clavatecheilocystidia, it is apparent that they are much shorter and less clavate than one would expect from species of H. sect. Velutipes. The cylindrical cystidia suggest to place this taxon in H. sect. Scabrispora and indeed it does appear to have some characters in common with species of this section, but our phylogenetic results do indicate that this and a few related taxa (see above) be treated as a separate section and hence we have erected Hebeloma sect. Naviculospora. While H. naviculosporum is rare but widespread within Europe, we already know that it (or a taxon very similar) also exists within North America and indeed we have already examined material from North America of other taxa from this same section (not yet known from Europe) and closely related to H. naviculosporum. We would not be surprised to find this species to be common in North America, but any further discussion is beyond the scope of this book.

Geographic distribution

Phenology

• arrow_drop_downarrow_drop_upAdditional cited collections

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