Hebeloma alpinum (J. Favre) Bruchet, Bull. Mens. Soc. Linn. Lyon 39 (6 suppl.): 68 (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 : 24

7. Hebeloma alpinum (J. Favre) Bruchet, Bull. Mens. Soc. Linn. Lyon 39 (6 suppl.): 68 (1970) Figures 4A, 13, 23 (7)

Etymology.

alpinum from the alpine.

Description.

Cortina absent. Pileus 20-35 mm in diameter, convex to broadly domed, buff to pale brown, rarely brown, slightly paler at margin but not two-toned, smooth, cracking when dry; margin turned down or in. Lamellae attached, emarginate, somewhat broad, pale milk coffee, L = 40-70 plus lamellulae; edges white fimbriate, beaded. Stipe 15-30 × 4-10 mm, rather short, equal, sometimes slightly restricted in middle, clavate, white, firm. Context buff. Odor slightly raphanoid. Exsiccate: pileus brown, slightly caramel color; lamellae dark rusty brown; stipe short, cream color.

Basidiospores yellowish brown, amygdaliform with a snout, more symmetrical in side view, apiculate, sometimes guttulate, weakly ornamented (O1, O2), no loosening perispore noted (P0), very slightly dextrinoid (D0, D1), 10-12 × 6-7 µm, on average 11.2 × 6.6 µm, a few large spores present -18 × -8 µm, Q = 1.69. Basidia 32-40 × 8.5-10.5, mainly four-spored, some possibly two-spored. Cheilocystidia mostly clavate-stiptate, 55-75 µm long, apex width 6.5-10.5 µm, median width 4-5.5 µm, base width 3.5-4.5 µm. Pleurocystidia absent. Epicutis thickness 60-160 µm, with some encrusted hyphae.

Rocky Mountain ecology.

Information is based on one collection from Montana, with mixed dwarf and shrub Salix species.

Rocky Mountain specimens examined.

U.S.A. MONTANA: Park County, Lulu Pass, 3000 m in Salix arctica and S. glauca , 11 Aug 2012, CLC2855 (MONT), C. Cripps.

Discussion.

The only confirmed report we have for this species from the Rocky Mountains relies on a single collection of a few specimens found near Cooke City, Montana at an elevation of 3000 m with dwarf and shrub Salix species. In the network Fig. 4A, this single RM representative of H. alpinum appears rather distant from its European counterparts, which are clustered at one of the centers of the network, i.e. the biggest circle, of the H. alpinum complex. An ITS tree including the H. alpinum complex is given in Eberhardt et al. (2015a). Although this collection appears molecularly quite far removed from its conspecifics, 6-10 [1-2] bp, the total distance is largely due to a 5 bp indel repeating a sequence motif generally present in members of the H. alpinum complex. Thus, the molecular results do not argue against this being H. alpinum . This species is quite variable molecularly as well as morphologically (see the discussion of the alpinum -complex in Beker et al. 2016). The spores of this collection are on the lower end of the range for this taxon, as given in Beker et al. 2016, but still comfortably within the range.

Hebeloma alpinum has been reported previously in North America from the Rocky Mountain alpine zone ( Cripps and Horak 2008) and Alaska ( Miller 1998), however, most sightings were not molecularly confirmed. There are three records from the Canadian Arctic collected in 1971 and 1974 ( Ohenoja and Ohenoja 2010), which have been confirmed molecularly ( Beker et al. 2018). Ten collections at the Denver Botanic Garden, originally labeled H. alpinum , are now molecularly confirmed as H. hiemale (see comments for this species).

Favre originally described this species from the Swiss Alps as Hebeloma crustuliniforme var. alpinum Favre ( Favre 1955) and Bruchet (1970) elevated it to species level. Hebeloma alpinum appears confined to arctic-alpine habitats and has been reported from such regions of the European Alps, Carpathians, Pyrenees, Greenland, Iceland, Scandinavia, Svalbard, and Switzerland, primarily with Salix reticulata , S. polaris , S. retusa , and Dryas octopetala as well as Persicaria ( Beker et al. 2016). The species is in H. sect. Denudata , subsect. Crustuliniformia because of the lack of a veil, the clavate-stipitate shape of the cheilocystidia and molecular data ( Eberhardt et al. 2015a). As a relatively robust alpine species, it should be compared to H. hiemale and H. velutipes ; the latter has a robust floccose white stipe.