Hebeloma avellaneum Kauffman, Papers of the Michigan Academy of Sciences 17: 171 (1933)

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 : 20

5. Hebeloma avellaneum Kauffman, Papers of the Michigan Academy of Sciences 17: 171 (1933) Figures 3, 11, 23 (5)

Etymology.

For the color of hazelnuts, such as Corylus avellana .

Description.

Cortina absent. Pileus 20-40 mm across, hemispherical, convex, can be domed, glabrous-viscid, rich Sayal brown, ochraceous to orange brown, cinnamon brown, with frosty canescence; margin turned down, or rolled in, remaining light colored, downy. Lamellae adnate to subdecurrent, narrow, L = 90 plus lamellulae, pale avellaneous, pale cinnamon, not dark at maturity; edges floccose, beaded. Stipe 25-35 mm × 8-10 mm, equal to clavate, sturdy, white to cream, pruinose at apex, scurfy scales below. Context thick over pileus area, whitish, watery, not changing, or browning a bit in stipe but not from base up. Odor fruity or herbal tones. Exsiccate: medium-sized, cespitose in one group, hemispherical with margin inrolled, evenly colored, ochraceous, smooth to aereolate; stipe white, sturdy.

Basidiospores yellowish brown, amygdaliform, with a small apiculus, weakly ornamented (O1, O2), loosening perispore observed in a few spores (P0, P1), distinctly dextrinoid (D3), 8-11 × 5-6 µm, on average 9.5 × 5.4 µm, Q = 1.76. Basidia 25-34 × 6.5-8.5 µm, two- and four-spored. Cheilocystidia variable, many cylindrical, but also gently clavate, capitate and capitate-stipitate as well as clavate-lageniform, 30-80 × 4 –13(– 15) µm at apex, 3.5-6.5 µm in middle, and 4 –8(– 9) µm at base. Pleurocystidia absent. Epicutis thickness 80-130 µm, no encrusted hyphae recorded.

Rocky Mountain ecology.

Cespitose, or clustered, in low alpine krummholz with conifers and willows. Both collections we have studied are from Colorado.

Rocky Mountain specimens examined.

U.S.A. COLORADO: Summit County, Loveland Pass Lake, 4000 m, under willows, 20 Aug 1999, DBG-F-020434, no conifers mentioned but present in the general area, O.K. Miller Jr; Boulder County, above Mountain Research Station, 3200 m, with small willows ( Salix planifolia ) and one spruce within 2 m, 1 Aug 1998, DBG-F-019533, V.S. Evenson.

Other American specimens examined.

U.S.A. WASHINGTON: Grays Harbor County, Lake Quinault, Olympic National Park, at 75 m, on mossy edge of forest clearing, 8 Nov 1925, MICH 10722, C.H. Kauffman (holotype). CANADA. NEWFOUNDLAND AND LABRADOR: Pinware River at 15 m, under conifers, 7 Sep 2005, HJB14320, leg. J. May.

Discussion.

Based on ITS data, H. avellaneum is monophyletic, but unsupported by bootstrap values (Fig. 3). In terms of phylogeny, its closest relative is H. catalaunicum Beker, U. Eberh., Grilli & Vila, a Mediterranean species. It is also close to H. naviculosporum Heykoop, G. Moreno & Esteve-Rav. and H. nanum Velen. All three species appear to associate with Pinaceae ( Beker et al. 2016). The identification of H. avellaneum is supported by type studies. The fourth collection used in Fig. 3 is from Canada (Newfoundland) and has been presented by Voitk et al. (2016) as " Hebeloma sp. sect. Naviculospora ".

Based on our studies of this taxon and of the habitats where it has been collected, we strongly suspect that this species is typically associated with conifers in temperate to subalpine or subarctic habitats. The holotype was collected in a temperate rainforest within the Olympic Peninsula in western Washington state. The often pruinose pileus with distinctive orange tones is indicative of H. sect. Naviculospora . These specimens were found in the low alpine where conifers are possible, and indeed Picea was noted for one collection, but only willows for the other. In the low alpine of the Rocky Mountains, the species might be confused with H. alpinum , H. velutipes , or H. hiemale because of its robust habit and lack of veil, however there are more orange color tones of the pileus; the spores are smaller and more dextrinoid than one would expect for H. alpinum and H. hiemale .