Hebeloma oreophilum Beker & U. Eberh., Mycologia 107: 1295 (2016) [2015]

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 : 35-36

13. Hebeloma oreophilum Beker & U. Eberh., Mycologia 107: 1295 (2016) [2015] Figures 6A, 19, 23 (13)

Etymology.

From oreophilus, mountain loving to emphasize its presence in alpine habitats.

Description.

Cortina present. Pileus 15-30 mm in diameter, convex, hemispherical, not umbonate, smooth, dry or greasy, medium brown, bay brown, reddish brown, dark black brown, with white to cream rim of fibrillose veil remnants at margin, with hoary coating; margin even or weakly scalloped. Thick waxy pellicle mentioned in one collection. Lamellae emarginate, subdistant, L = 40-50 plus lamellulae, cream at first then milk coffee color, pinkish cinnamon; margin floccose, white. Stipe 15-60 × 3-8 mm, equal or slightly enlarged at base, a bit curved or undulating, whitich, tan, brown, in top part and darkening to blackish brown at base, pruinose in top half and fibrous below, with patches of fibrils. Context watery buff with yellow tint, and blackish brown in base, stipe hollow. Odor raphanoid. Exsiccate pale brown all over, not dark.

Basidiospores amygdaliform, with a small snout, apiculate, not guttulate, finely verrucose (O1, O2), distinctly dextrinoid (D2, D3), no perispore loosening observed (P0), 10-14 × 6-8 µm, on average 11.7 × 6.9 µm, Q = 1.68. Basidia clavate, 25-35 × 8-10 µm, mostly four-spored. Cheilocystidia lageniform, with subcapitate apex, long neck (sometimes wiggly), with gradually swollen base, sometimes septate, length 30-70 × 4-7 µm at apex, 3-6.5 µm in middle, and up to 13 µm at base, no thickening noticed. Pleurocystidia absent. Epicutis thickness 40-75 µm, with no encrusted hyphae recorded.

Rocky Mountain ecology.

In low alpine with Salix species in Montana and Colorado.

Rocky Mountain specimens examined.

U.S.A. COLORADO: Clear Creek County, Denver Mountain Park, Summit Lake, 3911 m, in Salix arctica and S. glauca , 20 Aug 2013, DBG-F-027674, L, Gillman; Summit Lake Park, 3912 m, with Salix sp., 22 Aug 2012, DBG-F-022788, L. Gillman; Arapaho National Forest, Nature Trail, Mount Goliath, 3658 m, in Salix sp, 1 Sept 1999, DBG-F-020558, V.S. Evenson; Pitkin County, White River National Forest, junction of Montezuma Basin and Pearl Pass, in Salix sp., 3658 m, 6 Aug 1999, DBG-F-020053, V.S. Evenson. MONTANA: Carbon County, Beartooth Plateau, Frozen Lakes, with dwarf Salix , 26 July 1997, 3200 m, CLC1102 (MONT), C. Cripps; site 2, 3100 m, 8 Aug 2002, CLC1937 (MONT), with Salix planifolia , C. Cripps; Billings Fen, in moss near S. planifolia , 3048 m, 23 Aug 2017, CLC 3607 (MONT). WYOMING: Beartooth Plateau, Wyoming Creek, with Salix planifolia , 3176 m, 6 Aug 2008, HJB12449, C. Cripps; Beartooth Plateau, Hell-roaring Plateau, near Salix sp., 14 Aug 2007, ZT12733 (ETH), E. Horak.

Discussion.

Hebeloma oreophilum is a member of the H. nigellum complex that cannot always be distinguished from H. nigellum based on ITS data (Fig. 6A). In terms of differences, the H. oreophilum sequences from the sample (9 RM, 10 FE) differ by 0-9 [0-3] bp; 0-8 [0-1] bp within the RM sample. Most similar to H. oreophilum is H. clavulipes , which in this sample differs by 1-11 [0-3] bp. The two species do not share the same habitats. The differences between species sharing the same habitats ( H. nigellum and H. spetsbergense ) are 3-10 [0-5] bp. Morphologically, the easiest way to separate H. oreophilum from H. hygrophilum and H. nigellum is by the number of full length lamellae, always at least 40 for H. oreophilum and less than 36 for the others. Hebeloma clavulipes is not known from arctic-alpine habitats and has spores with an average width at most 6.6 µm while the average spore width for H. oreophilum is on average at least 6.8 µm. Hebeloma oreophilum has a persisting cortina and the lageniform/ventricose cheilocystidia of H. sect. Hebeloma .

This species was first described from the western Carpathians (Slovakia) with Salix reticulata , S. retusa , or Dryas octopetala on calcareous soil ( Eberhardt et al. 2015b). It has since been reported from Canada, Greenland, Scandinavia, Svalbard, and the Rocky Mountains ( Beker et al. 2016; Beker et al. 2018).