Helvella rivularis Dissing & Sivertsen

Helvella rivularis Dissing & Sivertsen (FIGURE 3) Description:—Apothecia compressed cup shaped or discoid when young, later saddle-shaped or irregularly expanded to flat, 5–20 mm across, margin free and often inrolled, hymenium more or less pubescent, dark-greyish to brown with bluish-brown tints, receptacle surface finely villose especially when young, same color as hymenium or somewhat darker (FIGURE 3A). Stipe 2–15 mm long, 1–5 mm broad, solid, slightly curled cylindrical sometimes expands towards the pileus, conspicuously pubescent, whitish to cream or pale grey (FIGURE 3A). Ectal excipulum 190–230 µm thick, of textura angularis or textura prismatica, outer cells cylindrical or clavate, hyaline. Medullary excipulum 320–350 µm thick, of textura intricata, hyphae 3–4 µm thick, septate and branched, hyaline. Asci 300–360 × 16–24 μm, 8-spored, uniseriate, cylindrical, tapers towards the base, almost all pleurorhynchus (Figs 3B, C, D). Paraphyses filiform, septate, somewhat branched, 3–4 µm thick, thickened at the tip to 5–10 µm, slightly exceeding the asci (Figs 3B, C). Ascospores (16) 17.5–22 (23) × 11–14.5 µm, Q = (1.4) 1.5–1.8, ellipsoid, smooth, hyaline and uniguttulate (Figs 3E, F, G). Specimen examined: — Türkiye, Erzurum-Kars province, Şenkaya district, under conifer trees, 40°34’51”N 42°23’43”E 2373 m, 03.06.2021, ME 714, VANF 7891. Habitat and distribution: —Grow often 10–20 gathered or rarely solitary, at the subalpine to alpine zones, among hygrophilous mosses and on the calcareous sand (Dissing & Sivertsen 1980, Carbone 2011, Skrede et al. 2017). Notes: — Helvella rivularis shares morphological, ecological and phylogenetic similarities with H. multiformis and H. sublicia. However, these species can be distinguished by several features. Helvella multiformis has lighter-colored caps and shorter, thinner ascospores, with a maximum length of 20 µm and a width of 13 µm, resulting in smaller asci (Mao et al. 2023). Helvella sublicia can be distinguished by its near-white to greyish hymenium surface, sub-pubescent to villose receptacle, and narrower ellipsoid ascospores (Skrede et al. 2017, 2020). Molecular data, including combined and three single-locus datasets, further supports the separation of H. rivularis from its close relatives (FIGURE 1 and S1-S 3). In the aligned concatenated dataset, 98 nucleotide differences were identified between H. rivularis and H. multiformis (ITS: 63, LSU: 17, TEF 1-α: 18), and 98 variations between H. rivularis and H. sublicia (ITS: 60, LSU: 18, TEF 1-α: 20).