Cortinarius alutarius Kałucka & Liimat., sp. nov.

Index Fungorum number: IF 558552; MycoBank number: MB 558552; Facesoffungi number: FoF 09966; Fig. 1

Etymology – The name is based on a Latin adjective alutarius (made of soft leather), referring to the suede-like cap surface.

Holotype – LOD(F):47001

Pileus 1.5–2.5 cm in diam., at first conical, later low conical to almost plane, with±distinct umbo, tomentose, floccose to finely scaly, dark rusty brown, cinnamon brown, usually darker at the centre and paler, ochraceous to buff, towards the margin, light brown or ochraceous when dry; hygrophanous. Lamellae fairly distant to medium spaced, adnate to emarginate, medium brown to dark brown, the edge may be paler, at least when young. Stipe 3–4 cm long, 0.2–0.4 cm thick, cylindrical, fibrillose, ochraceous buff-brown, becoming brownish to dark brown from base upwards with age or after handling. Context brown, darkening when old or bruised. Universal veil white to cream buff, distinct on the cap margin, forming fine stripes and incomplete girdles on the stipe. Odour not recorded. Basidiospores 6.5–7.5×4.5–5 µm, av.=7×5 µm, Q =1–1.5, Qav.=1.5, ellipsoid to somewhat obovoid, finely to moderately verrucose, especially at the apex, indextrinoid to weakly dextrinoid (developing dextrinoid reaction very slowly to dextrinoid after a few hours), fulvous brown in 10% KOH, spore deposit rusty brown. Basidia 19–25×6–9 μm, clavate, with four sterigmata; sterile cells distinct on the gill edge, clavate, apex 5–12 µm wide, av.=8 µm. Lamellar trama hyphae light ochraceous brown, smooth, with parallel streaks of parietal to encrusting dark brown, amber-like pigment, at places with pigment lumps in the corners near septa. Pileipellis: Epicutis thin, of hyaline, pale, ±parallel hyphae 4–11 µm, av.=7 µm, smooth, with yellowish parietal pigment, with frequent ascending bundles consisting of appressed thick-pigmented hyphae or/and thin-walled hyphae slightly constricted at septate, mixed with hypoderm elements, some with end cells swollen, 13–23 µm wide, av.=16.5 µm (bundles visible as fine flocs under the dissecting microscope). Hypoderm consisting of inflated elements 21–52 × 10–21 µm, av.=31 × 14 µm, smooth, some thin-walled and some with parietal pigment, in deeper parts with fine, spot-like encrustations. Trama pale brown, consisting of parallel hyphae 3–7(–8) µm wide, av.=5 µm, smooth with numerous spots and streaks of parietal to encrusting dark brown, amber-like pigment and lumps of pigment near the septate, in deeper layers of subcellular elements 37–44 × 13.5–23.5 µm, av.=41 × 18 µm, with much less distinct spot-like encrustations and yellowish pigment. ITS sequence (GenBank MZ648197, holotype) differing from the most similar sequences available with at least 9 substitutions and indels. Distinct from other members of Cortinarius sect. Rubricosi and deviating from them with at least 17 substitutions and indels.

Ecology and distribution – In temperate (possibly also boreal) pine forests on acid soil, growing in groups of sporocarps; basidiomata found in August. So far known from one locality and one collection only.

Material examined – POLAND, Mt Kamieńsk lignite mine spoil heap near Bełchatów, young Pinus sylvestris plantation on strongly to slightly acid loamy sand, 0–0.45% CaCO3, 2 August 2011, leg. I.L. Kałucka 00220 (LOD(F):47001, holotype), K(M), isotype.

GenBank number – ITS=MZ648197.

Notes – This species is only known from one locality in Poland, on Mt Kamieńsk, the outer spoil heap of the Bełchatów opencast lignite mine, in ca. 20 year old pine plantation (Pinus sylvestris L.), on mineral soil among short mosses, lichens and pine needles, on strongly to slightly acid loamy sand, 0–0.45% CaCO3. The presence of Betula or Salix in the vicinity cannot be excluded. As at the same locality many rare species of northern distribution have been found (Kałucka et al. 2016), we suspect that the species can occur also in Northern Europe. Cortinarius alutarius has finely tomentose-floccose dark rusty brown cap drying to light ochraceous brown, ochraceous brown stipe darkening from base upwards and ellipsoid-obovoid moderately verrucose spores (Fig. 1). It is distinct from known closely related species, like C. subscotoides, C. scotoides, C. minusculus, C. rubricosus and C. comptulus and can be relatively easily distinguished based on the combination of the basidiomata habit, spore measurements and habitat type. Cortinarius alutarius fits well in the C. sect. Rubricosi Bidaud, Moenne-Locc. & Reumaux (Fig. 2). Based on the molecular and morphological data, the species is described here as new.

Figure 1 – Cortinarius alutarius (LOD(F):47001, holotype). a Basidiomata. b Basidiospores. c Pileipellis structure. d, e Ascending elements of pileipellis. Scale bars: a=20 mm, b=10 µm, c–e=20 µm

Figure 2 – Phylogram resulting from the RAxML (Stamatakis 2014) analysis of ITS region. Bootstrap values equal to or greater than 50% are indicated above the nodes. The specimens in boldface represent the type specimens of the species. The newly generated sequences are in blue