Cortinarius mammillatus Kałucka, Kytöv., Niskanen & Liimat., sp. nov.

Index Fungorum number: IF 558553; MycoBank number: MB 558553; Facesoffungi number: FoF 09967; Figs. 1, 2

Etymology – The name is based on a Latin adjective mammillatus (having the form of a bluntly rounded protuberance) referring to a distinct nipple-like umbo.

Holotype – LOD(F):48001

Pileus 1.5–3 cm in diam., distinctly umbonate, with pronounced,±acute to bluntly rounded umbo, glabrous, finely tomentose-fibrillose towards the margin, fulvous brown, ochraceous orange brown, drying mat with radial lighter stripes to pale grayish/yellowish/orange ochraceous; hygrophanous, striate. Lamellae medium spaced, adnate to emarginate, medium rusty brown, edge concolour or slightly paler, especially near the margin and when young. Stipe 5–9(–11) cm long, 0.2–0.5 cm thick at apex, cylindrical, sometimes slightly wider at the base, whitish silky fibrillose to sparsely flocculose on ochraceous to rusty brown background. Context: in pileus brown, in stipe paler, ochraceous brown. Universal veil white, fibrous to floccose. Odour in lamellae of cedar wood, sometimes with raphanoid note; at the base of stem iodoform-like, best observed when slightly dried. Basidiospores 7.5–8.5(–9) × 4.5–5.5 µm, av.=8 × 5 µm, Q =1–2, Qav.=1.5, narrowly ellipsoid to ellipsoid to ellipsoid-amygdaloid, finely to moderately evenly verrucose, dextrinoid to distinctly dextrinoid, olive yellowish brown in 10% KOH, spore deposit medium brown. Basidia 24–34×6–7 µm, narrowly clavate, with four sterigmata. In KOH, many basidia and basidioles yellowish olivaceous or amber brown. Lamellae edge mostly fertile, with sterile cells close to the cap margin; sterile cells broadly clavate to balloon-shaped, apex 7–13 µm wide, av.=10 µm, usually on short basal cells. Lamellar trama hyphae pale olive yellowish, yellowish to orange brown in KOH, yellowish to orange yellow parietally encrusted, with streaks and lumps of amber-like pigment, numerous hyphae densely finely scabrous. Pileipellis: Epicutis of hyaline, pale, parallel hyphae 5–11 µm, av.=8 µm, smooth, some with yellowish parietal encrustation. Hypoderm consisting of inflated subcellular elements and inflated hyphae, (24–)28–58(–80) × 13–25(–26) µm, av.=41.5 × 18.5 µm, smooth, some yellowish, yellowish ochraceous parietally encrusted, some with fine, spot-like encrustations to scabrous, and some with small lumps of olive ochraceous pigment, especially in deeper parts. Trama ochraceous brown, olive brown, consisting of±parallel hyphae, 6–14 µm wide, av.=10.2 µm, smooth to finely scabrous, with thin to thick parietal encrustation, some with olive brown to amber brown, spot-like encrustations or lumps of pigment, especially near the septa, in deeper layers of subcellular elements 45–68×12–19 µm, av.=56×16 µm with similar pigmentation. ITS sequence (GenBank MZ648201, holotype) differs from other sequences of C. sect. Obtusi known to occur in the Northern hemisphere with more than 20 substitutions and indels.

Ecology and distribution – In boreal and mountainous coniferous forests of the northern hemisphere, growing in groups of sporocarps; basidiomata found in September and October.

Material examined – POLAND, Sudetes, Stołowe Mountains National Park, Czerwona Woda River valley, Picea abies old-growth forest, among Polytrichum moss, 15 September 2017, leg. I.L. Kałucka 17–140, (LOD(F):48001, holotype; K(M), isotype); loc. cit., among Sphagnum and Polytrichum mosses, 19 October 2017, leg. I.L. Kałucka 17–153 (LOD(F):48002); loc. cit., among Sphagnum and Polytrichum mosses, 18 September 2017, leg. I.L. Kałucka 17–159 (LOD(F):48003); loc. cit., among litter, grass and mosses, 7 September 2017, leg. I.L. Kałucka 17–160 (LOD(F):48004). FINLAND, Uusimaa, Sipoo, Paippinen, 14 Sep 2004, leg. K. Liimatainen and T. Niskanen 04–814 (H:6030110); Satakunta, Säkylä, Virttaankangas, Porsaanharju, pine (Pinus sylvestris) heath forest on sandy soil, 19 October 2006, leg. K. Liimatainen and T. Niskanen 06–249 (H:6029329). UK, Scotland, Woodcock Hill Plantation, in conifer plantation, under Picea, 21 October 2018, leg. D.J. Savage 488/18 (K(M):262938). CANADA, Ontario, Nipissing, Algonquin Provincial Park, Wildlife research station, chit lake trail, mixed forest of deciduous (e.g. Betula) and coniferous trees (e.g. Abies balsamea), 13 September 2007, leg. K. Liimatainen and T. Niskanen 07–172 (H:7000834); Newfoundland, west coast Gros Morne National Park, N end of the Bonne Bay’s Eastern Arm, James Callaghan hiking trail to Gros Morne Mountain, mesic to moist Abies balsamea dominated forest with some Picea, Alnus, and Betula, collected under Alnus, 21 September 2007, leg. K. Liimatainen and T. Niskanen 07–272 (H:7000935); Newfoundland, Avalon Peninsula, Salmonier Nature Park, mesic to moist Picea dominated forest with some Abies, Betula and Larix, 26 September 2007, leg. K. Liimatainen and T. Niskanen 07–299 (H:7000963); Newfoundland, 26 September 2007, leg. A. Voitk 2–101 (K(M)); Newfoundland, west coast Gros Morne National Park, N end of the Bonne Bay’s Eastern Arm, James Callaghan hiking trail to Stuckless Pond, mesic to moist Abies balsamea dominated forest with some Picea, Alnus, and Betula, 19 September 2010, leg. K. Liimatainen and T. Niskanen 10–106 (H). USA. Washington, Snohomish county, Barlow past, Mt. Baker Snoqualmie National Forest, mixed coniferous forest, mainly Tsuga heterophylla with some Pseudotsuga menziesii and Abies amabilis, 10 October 2009, leg. K. Liimatainen and T. Niskanen 09–077 (H).

GenBank number – LOD(F):48001: ITS= MZ648201; LOD(F):48002: ITS = MZ648202; (LOD(F):48003): ITS = MZ648203; LOD(F):48004: ITS = MZ648204; H:6030110: ITS=MZ648205; H:6029329: ITS=MZ648206; H:7000834: ITS=MZ648208; H:7000935: ITS=MZ648209; H:7000963: ITS = MZ648210; K(M): A. Voitk 2–101: MZ648211; H: K. Liimatainen and T. Niskanen 10–106: MZ648212; H: K. Liimatainen and T. Niskanen 09–077: MZ648213; K(M):262938: ITS=MZ648207.

Notes – The type collection and other three collections from Poland come from the mossy old-growth spruce (Picea abies) forest growing along the mountain stream (Pielech et al. 2018). In Finland, the species was found in pine (Pinus sylvestris) heath forest on sandy soil. All the North American collections are from mixed coniferous forests, with Abies, Picea and Betula on the east coast and Tsuga, Pseudotsuga and Abies on the west coast. A number of sequences available in GenBank and UNITE repositories, which do not differ from the type sequence by more than 3 substitutions and indels, come from the ECM roots of Pinus sylvestris (AY641464, Scotland) and Picea rubens (MK131478, MK131479, Canada), soil DNA from Cedar-Hemlock and Hemlock-Amabilis Fir Forests (KP889457, Canada) as well as sporocarps identified as C. obtusus from Picea abies forests (KY287715, KY287718, KY287698, Tatra Mts, Slovakia; AJ238035=UDB000127, Norway). Cortinarius mammillatus has distinctly umbonate, fulvous brown, striate hygrophanous cap, glabrous with tomentose margin, slender, whitish silky fibrillose stipe and narrowly ellipsoid to ellipsoid-amygdaloid, verrucose spores (Figs. 1 and 2). It most resembles C. obtusus and C. acutus. The former is somewhat fleshier and has more slender spores with coarser ornamentation; the latter has a usually more conical cap with pointed umbo, lighter gills and thinner, more brittle stipe; both species have a greater proportion of gill edge whitish fimbriate. C. fulvescens has darker cap centre, pale pink universal veil and slightly longer spores. Cortinarius mammillatus formed a well-supported clade (100% MLBS; Fig. 3) and based on the molecular and morphological data is described here as new.

Figure 1 – Cortinarius mammillatus (LOD(F):48001, holotype). a Basidiomata. b Basidiospores. c Pileipellis structure. Scale bars: a=20 mm, b=10 µm, c=20 µm

Figure 2 – Cortinarius mammillatus—additional collections (basidiomata). a H:7000935. b H:7000963. c LOD(F):48003. d LOD(F):48004. e LOD(F):48002. f LOD(F):48002a. Notes: Photographs: a, b K. Liimatainen, c–f I.L. Kałucka

Figure 3 – 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