Hebeloma subconcolor Bruchet, Bull. Mens. Soc. Linn. Lyon 39 (6, suppl.): 127 (1970)

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 : 17

3. Hebeloma subconcolor Bruchet, Bull. Mens. Soc. Linn. Lyon 39 (6, suppl.): 127 (1970) Figures 5, 9, 23 (3)

Etymology.

concolor for the similar coloration of pileus and stipe, which is not a consistent feature.

Description.

Cortina absent. Pileus 15-20 mm, convex, with or without a low broad umbo, becoming plane, smooth, moist, light to medium brown, pruinose with a grayish tint or sheen, lighter towards margin but not distinctly two-toned; margin turned down or not, entire. Lamellae adnexed, subdistant, well-separated, medium broad to broad, L = 25-32 plus lamellulae, dull brown, light brown; edges lighter. No beaded drops reported. Stipe 15-30 × 3-4 mm, equal, apex somewhat lighter tan and pruinose, below totally covered with longitudinal white fibers over a brownish ground base. Context buff. Odor astringent. Exsiccate: pileus medium brown, not two-toned, with grayish tint, dull; lamellae broad, warm cinnamon; stipe long, dull brown, narrow.

Basidiospores yellowish brown, amygdaliform, with a small apiculus, weakly ornamented (O2), loosening perispore observed in a few spores (P0, P1), distinctly dextrinoid (D2, D3), 10.5-12.5 × 6.5-7.5 µm, on average 11.6 × 7.1 µm, Q = 1.65. Basidia 25-34 × 8-10 µm, four-spored. Cheilocystidia gently clavate, some slightly swollen at apex and base, 40-60 × 6-11 µm at apex, 4.5-7 µm in middle, and 4-7 - (8) µm at base. Pleurocystidia absent. Epicutis thickness 60-75 µm, with some encrusted hyphae.

Rocky Mountain ecology.

Two collections reported under willow at alpine elevations of 4000 m in Colorado; noted as cespitose to gregarious.

Rocky Mountain specimens examined.

U.S.A. COLORADO: Clear Creek County, Summit Lake Park, under Salix , some in moss, at 4000 m, 22 Aug 2012, DBG-F-022785; DBG-F-022786, L. Gillman.

Discussion.

The sequences of the two collections for H. subconcolor from the Rocky Mountains are identical. The RM sequence differs by 1-4 [0] bp from the H. subconcolor collections described in Beker et al. (2016) and Grilli et al. (2016), where the ITS ML results were also shown. The closest H. velutipes sequence included in the dataset used in Fig. 5 differs in 3 [0] bp. Hebeloma velutipes is the only species of Hebeloma that cannot be distinguished from H. subconcolor by ITS sequence ( Beker et al. 2016; Grilli et al. 2016; Fig. 5). However, morphologically these two species are very different and can be easily separated.

This small species has a grayish cast not found in other taxa in sections Denudata and Velutipes that we report from the Rocky Mountains; also, the lamellae are well separated and few in number. It should be compared to the other non-veiled, small species such as H. aurantioumbrinum and H. vaccinum . Hebeloma velutipes has a different coloration and is larger with many more full length lamellae. Hebeloma subconcolor is known from arctic and alpine locations in the European Alps, Greenland, Iceland and Scandinavia ( Beker et al. 2016, 2018).