Hebeloma dunense L. Corb. & R. Heim, Mem . Soc. Natn. Sci. Nat. Math. Cherbourg 40: 16 (1929)

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 : 29-32

10. Hebeloma dunense L. Corb. & R. Heim, Mem. Soc. Natn. Sci. Nat. Math. Cherbourg 40: 16 (1929) Figures 6B, 16, 23 (10)

Etymology.

Originally found in sand in dunes.

Description.

Cortina present. Pileus 10-28 mm in diameter, convex, slightly conic-convex, with or without a slight umbo (one papillate), or almost applanate, some sunken in center, smooth, greasy, pale pinkish buff at first, becoming caramel color in center, outwards remaining pale, with a hoary coating, some flecks of white in outer part, mostly appearing pale unicolor; margin turned in or down, covered with white veil tissue or not. Lamellae emarginate to subdecurrent, or pulling away, variable, L = 25-48 plus lamellulae, a bit distant, cream buff to pinkish buff at first, then milk coffee; edges white fimbriate. Stipe 20-50 × 2-6 mm, equal or narrowing a bit at base, dingy whitish buff in top part, sometimes pruinose and base darkening to golden color then blackish brown (not always obvious unless cut open), with fibrils on lower part and /or a few 'patches of tissue’. Context dingy white, watery buff, dark at base, sometimes splitting, often hollow when mature; tough in base. Odor faintly raphanoid or absent. Exsiccate: mostly pale; pileus buff or more ochraceous buff, center a bit caramel or not; lamellae pale light ocher; stipe buff, not obviously darker at base.

Basidiospores yellowish gray in Melzer’s, mostly elliptical, a few slightly amygdaliform but typically without much snout, no big apiculus, not guttulate, look smooth but may be slightly rough in Melzer’s (O1, O2), not or only very slightly dextrinoid (D0, D1), and no perispore loosening (P0), 9.5-11.5 × 5.5-7 µm, on average 10.3 × 6.2 µm, Q = 1.65. Basidia 20-30 × 8-9 µm, clavate, four-spored mostly. Pleurocystidia absent. Cheilocystidia cylindrical in the upper part and slightly swollen to more swollen at the base, 40-55 µm long × 4.5-6 µm at apex, 4-6 µm in middle, and 7-10.5 µm wide at base, with occasional thickening of the apical wall, some septate and clamped; many with dense yellow contents. Epicutis thickness 25-75 µm, with some encrusted hyphae.

Rocky Mountain ecology.

In the alpine zone of the San Juan Mountains, with dwarf willows S. reticulata and S. arctica , and shrub willow S. planifolia , some in moss or near streams.

Rocky Mountain specimens examined.

U.S.A. COLORADO: San Juan County, San Juan Mountains, Cinnamon Pass, 3700 m, with dwarf Salix near stream, 29 July 2000, CLC1411 (MONT), C. Cripps; with Salix reticulata , 8 Aug 2000, CLC1434 (MONT), C. Cripps; 29 July 2000 with Salix reticulata , ZT9001 (ETH), E. Horak; Stony Pass, 3840 m, with S. arctica , 28 July 2002, CLC1821 (MONT), C. Cripps; Mineral Basin, with S. arctica and S. planifolia , in moss, 3835 m, 30 July 2002, CLC1845 (MONT), C. Cripps.

Discussion.

Based on ITS data, Hebeloma dunense is phylogenetically not clearly distinguishable, but neither is it molecularly identical to other members of the H. mesophaeum complex (Fig. 6B). The intraspecific variation is 0-10 [0-2] bp (17 sequences), within the RM dataset (5 sequences), 1-7 [0-1] bp. The exclusively RM circle in Fig. 6B is a result of the data selection; this corresponds to ITS variants that do occur in the FE dataset, but did not come up in the random selection of sequences for this species.

For the Rocky Mountain collections, so far, H. dunense has been found more often with dwarf willows S. arctica , S. reticulata , and shrub willow S. planifolia in contrast to H. mesophaeum and H. excedens , which were more often with S. glauca . Originally described from low-elevation dunes with Salix , this species has been more recently recognized in arctic and alpine habitats and from Canada, Greenland, Svalbard, the European Alps, and the Carpathians ( Beker et al. 2016; Beker et al. 2018; Eberhardt et al. 2015b).

Rocky Mountain specimens of H. dunense are pale, often with narrow subdecurrent lamellae; the cortina can be scant or absent, some cheilocystidia have dense yellow contents, and the spores, which are ellipsoid and distinctly but not strongly ornamented, are slightly larger than those of H. mesophaeum and H. excedens .