Hebeloma hygrophilum Poumarat & Corriol, Fungi Europaei 14 (Lomazzo): 138 (2016)

Cripps, Cathy L., Eberhardt, Ursula, Schuetz, Nicole, Beker, Henry J., Vera S. Evenson, & Horak, Egon, 2019, The genus Hebeloma in the Rocky Mountain Alpine Zone, MycoKeys 46, pp. 1-54 : 36-38

14. Hebeloma hygrophilum Poumarat & Corriol, Fungi Europaei 14 (Lomazzo): 138 (2016) Figures 6A, 20, 23 (14)

Etymology.

hygrophilus, because it is often found in moist, wet, boggy ground.

Description.

Cortina present. Pileus 15-25 mm in diameter, convex to almost plane, smooth, greasy, center dark brown, reddish brown, lighter towards margin to buff; margin entire. Lamellae emarginate and strongly curved outwards, a bit distant, L = 24 plus lamellulae, pale buff becoming milk coffee color; edges lighter or darker. Stipe 25-35 × 1-2 mm, long and thin, undulating, dingy cream in top half, darkening to blackish at base, apex pruinose, below with longitudinal fibrils. Context dingy cream and brownish black in stipe base. Odor raphanoid. Exsiccate: small; pileus, two-toned, dark brown center, cream towards margin; stipe thin, whitish with a darker base.

Basidiospores slightly amygdaliform, a few with a snout, apiculate, not guttulate, finely verrucose (O2), distinctly dextrinoid (D2, D3), no perispore loosening observed (P0), 10-13 × 6-7.5 µm, on average 11.4 × 6.8 µm, Q = 1.67; a few spores larger -16 × -7 µm present. Basidia clavate, 25-30 × 7-9 µm, four-spored, possibly some two-spored because of larger spores present. Cheilocystidia lageniform, with subcapitate apex, long neck (sometimes wiggly), occasionally septate, with gradually swollen base, or almost cylindrical, length 35-70 × 4-6.5 µm or wider at apex, 4-6 µm in middle, and up to 7-13 µm at base, no thickening noticed. Pleurocystidia absent. Epicutis thickness 100-130 µm, with some encrusted hyphae.

Rocky Mountain ecology.

Based on four collections from Colorado and Montana, in the alpine zone; all with Salix , and the presence of Sphagnum is mentioned for one.

Rocky Mountain specimens examined.

U.S.A. COLORADO: Pitkin/Lake County, Sawatch Range, Independence Pass, 6 Aug 2000, under S. planifolia , 3660 m, CLC1462 (MONT), C. Cripps; 7 Aug 2000, Salix planifolia , CLC1476 (MONT), 3660 m, C. Cripps. Summit County, near Summit Lake, with Sphagnum sp. and Salix sp., 3658 m, 10 Aug 2003, DBG-F-021349, V.S. Evenson. MONTANA: Beartooth Plateau, Frozen Lakes, at 3200 m, near S. planifolia , 29 Aug 2002, CLC1948 (MONT), C. Cripps.

Discussion.

Figure 6A supports Beker et al. (2016) in that H. hygrophilum is paraphyletic in relation to the other members of the H. mesophaeum complex based on the ITS sequence, although some genotypes seem to be restricted to this species. The four H. hygrophilum representatives from the Rocky Mountains differ by 2-20 [0-2] bp in their ITS, whereas the intraspecific variation of H. hygrophilum within the sample is 1-22 [0-3] bp (14 sequences). Responsible for the high distance values is sample CLC1476 (HJB15297), which differs from all other conspecifics by 15-22 [0-1] bp and from all sequences of the ingroup by 14-22 [0-2] bp, while all other H. hygrophilum samples differ by only 1-9 [0-2] bp from each other. The morphologically closest taxon occurring in the Rocky Mountains is H. nigellum which differs by 3-10 [0-5] (14-21 [0-2]) bp. The values in round brackets are for CLC1476. An unusually high number of SNP positions in CLC1476 is responsible for the large total differences. However, sequences with numerous SNP positions occur occasionally in Hebeloma and are normally reproducable ( Beker et al. 2016).

Hebeloma hygrophilum was first described from the Pyrenees in non-alpine habitats above 1250 m ( Poumarat and Corriol 2009) and it is known in boreal habitats from northern Europe ( Beker et al. 2016). Thus it is typically in subalpine or subarctic habitats. It appears to have been found mostly with Salix and usually in wet areas with moss, typically Sphagnum . Here we report it for the first time in the alpine habitat (with S. planifolia ); at least one collection was found in Sphagnum moss. It is molecularly close to H. clavulipes , H. nigellum and H. oreophilum (see below). When found in the alpine, it could be confused with H. nigellum , which is morphologically very similar. However, the spore width of H. nigellum is reported typically with an average over 7 µm, while that for H. hygrophilum is reported with an average of less than 7 µm; to add confusion, both appear to have occasional very large spores likely from two-spored basidia.