Hebeloma islandicum Beker & U. Eberh.; Beker, Eberhardt & Vesterholt, Fungi Europ. (Alassio) 14: 414, 2016.

Eberhardt, Ursula, Beker, Henry J., Borgen, Torbjorn, Knudsen, Henning, Schuetz, Nicole & Elborne, Steen A., 2021, A survey of Hebeloma (Hymenogastraceae) in Greenland, MycoKeys 79, pp. 17-118 : 17

Hebeloma islandicum Beker & U. Eberh.; Beker, Eberhardt & Vesterholt, Fungi Europ. (Alassio) 14: 414, 2016. Fig. 35

Macroscopic description.

Cap 2.0-4.0 cm in diameter, convex to umbonate, margin involute when young, smooth, tacky when moist, not hygrophanous, uniformly colored or bicolored, at center dark olive buff to yellowish brown, at margin cream, innately fibrillose, sometimes with remnants of universal veil. Lamellae initially pale clay, in age often brownish, emarginate, maximum depth 5 mm, number of lamellae {L} 40-50, droplets visible with naked eye, with white fimbriate edge. Stem 1.7-2.5 × 0.4-0.6 {median} × 0.5-0.7 {base} cm, stem Q 3.4-5.5, whitish pale, finely flocculose-tomentose in the entire length with clavate base. Context firm, stem interior stuffed, later hollow, flesh usually discoloring from base. Smell raphanoid. Taste mild or slightly bitter. Spore deposit not recorded.

Microscopic description.

Spores amygdaloid, often limoniform, papillate, on ave. 11.0-12.5 × 6.5-7.0 µm, ave. Q = 1.7-1.8, yellow to yellow brown, guttulate, at most weakly ornamented ((O1) O2), perispore not or somewhat loosening (P0P1), weakly to rather strongly dextrinoid (D2D3). Basidia 28-40 × 6-9 µm, ave. Q = 3.7-4.9, mostly four-spored. Cheilocystidia irregular, a mixture of clavate-stipitate, clavate-lageniform, ventricose and slenderly clavate, with occasional characters, geniculate, septate (sometimes clamped) or rostrate, on ave. 44-55 × 6.5-8.5 (apex) × 4-5 (middle) × 4-8 (base) µm, ratios A/M = 1.63-1.98, A/B = 1.04-1.85, B/M = 1.05-1.73. Epicutis an ixocutis, up to 120 µm thick (measured from exsiccata), maximum hyphae width 6 µm, some encrusted, trama elements beneath subcutis ellipsoid, cylindrical, thick sausage-shaped up to 20 µm wide. Caulocystidia irregular like cheilocystidia up to 140 µm long.

Collections examined.

S-Greenland: Paamiut, N of town, 62.01°N, 49.4°W, 5 Sep 1986, T. Borgen (TB86.291, C-F-103573), 10 m, with Salix herbacea in snowbed.

Distribution.

Only one record, from southern Greenland. Until recently only known from the type from the north-western, arctic part of Iceland. As discussed above, two more collections have been discovered from herbarium exsiccata at O; both, collected in Norway at above 60°N at altitudes of more than 1000 m ( Eberhardt et al. in press). The above record from Greenland is from an arctic area and extends the distribution to North America. It is seemingly a very rare species. Although T.B. investigated the area around Paamiut regularly for 20 years, he only collected it once.

Habitat and ecology.

All four known collections appear to have been associated with Salix herbacea in a wet snowbed.

Notes.

Hebeloma islandicum was the only species recorded during the course of this study, which was not belonging to H. sects Denudata , Hebeloma or Velutipes . This species was described in Beker et al. (2016) on the basis of a single, but distinctive, collection from Iceland. The authors placed it within H. sect. Naviculospora . However, the authors acknowledged that it did not sit comfortably within any of their accepted sections. Within this section, this is the only species known to associate with Salix . Since its publication, two further collections have been discovered in Norway ( Eberhardt et al. in press).

Molecularly, this species is unambiguous. The ITS of the collection presented here is almost identical with the ITS of the type (693/694 pos. identical, all positions are matching (one G/T in the type sequence matched by a clean G). Most similar, but always less than 98% similar, are H. naviculosporum and H. nanum (both H. sect. Naviculospora ).

Figures

Figure 35. Hebeloma islandicum A TB 19.81, photograph T. Borgen B distribution of cited collections; C spores x 1600 and D cheilocystidia x 1000 of TB 86.291 in Melzer's reagent. Scale bars: 5 µm; microphotographs H. K. J. Beker.