Marasmius macrocystidiosus Kiyashko & E.F. Malysheva, 2014

Kiyashko, Anna A., Malysheva, Ekaterina F., Antonín, Vladimír, Svetasheva, Tatiana Yu. & Bulakh, Eugenia M., 2014, Fungi of the Russian Far East 2. New species and new records of Marasmius and Cryptomarasmius (Basidiomycota), Phytotaxa 186 (1), pp. 1-28 : 9-12

Marasmius macrocystidiosus Kiyashko & E.F. Malysheva , sp. nov. ( Fig. 2A , Fig. 3)

MycoBank 807119

Characterized by medium-sized collybioid basidiocarps with greyish brown or greyish orange tinges, broadly clavate or sphaeropedunculate, non-setulose pileipellis cells, well-differentiated hymenial cystidia and hyaline, more or less reniform spores with Q = 1.8–2.9. Caulocystidia sparse, sometimes roughly incrusted.

Holotype: RUSSIAN FEDERATION. Primorsky Territory: Sikhote-Alinsky State Nature Reserve, Golubichnaya bay, birch-larch-oak forest ( Betula mandshurica , Larix olgensis , Quercus mongolica ), on birch-larch litter, 44º54′24.3″ N, 136º32′04.0″ E, 21 Aug. 2011, A. Kiyashko ( LE 295996!), GenBank KF774136 for ITS, KF896246 for nrLSU.

Pileus to 30 mm diam. (dry specimen), plano-convex with slightly incurved, undulating and slightly plicate to pitted-rugulose margin, disc smooth to weakly rugulose, surface dull, glabrous, hygrophanous, pallescent from light brown (6D4, 7D4) or greyish brown (6D3) at disc to greyish orange (5 B 3) towards the margin. Flesh thin, whitish, unchanging on exposure. Lamellae adnate to adnexed, (sub)distant (appr. 29 reaching the stipe), broad (3–5 mm), whitish, with slightly eroded concolorous edge. Stipe 33 × 4 mm, cylindrical, slightly broadened towards base, longitudinally fibrillose and twisted, concolorous with the pileus margin, surface dull, dry, pruinose all over, base white tomentose. Odour and taste not defined.

Basidiospores 6.9–10.5(11.2) × 3.3–4.4 µm, χ m = 8.1±1.0 × 3.7±0.3 µm, Q = 1.8–2.9(3), Q m = 2.1±0.3, n = 45, s = 1; more or less ellipsoid, reniform to phaseoliform, smooth, thin-walled, hyaline, inamyloid. Basidia not observed. Lamella edge sterile. Cheilocystidia 28.0–66.3 × 7.7–11.4 μm, broadly fusoid, clavate or sub-cylindrical, sometimes septate, thin-walled, colourless, inamyloid. Pleurocystidia (35.6)78.3–123.0 × (7.5)12.5–13.8 μm, arising from subhymenium, fusiform, fusiform-ventricose, sometimes knobbed, thin-walled, with yellowish refractive content, inamyloid. Pileipellis a hymeniderm made up of Globulares - type cells, 10.9–29.6 × 7.9–21.6 μm, broadly clavate or spheropedunculate, occasionally with swollen, broad, rounded projections, with thickened, slightly pigmented walls or colourless. Stipitipellis consisting of parallel, cylindrical, incrusted hyphae, 3.5–5.0 µm diam., with more or less thinwalled, narrowly clavate, subcylindrical or near filamentous terminal cells. Caulocystidia sparse, various in shape, clavate, lageniform to slightly utriform or ventricose-rostrate, sometimes roughly incrusted, 25.3–41.1 × 6.0–15.4 µm, inamyloid. Clamp connections present in all tissues.

Etymology: Refers to the conspicuous large hymenial cystidia.

Habitat and distribution: Solitary on leaf-needle litter in mixed forest ( Betula mandshurica , Larix olgensis , Quercus mongolica ); Middle Sikhote-Alin and presumably Himalaya mountain systems.

Specimens examined: Holotype.

Observations: There are a few species in the section Globulares having both pleuro- and caulocystidia. The most morphologically similar taxon among them is Marasmius nigrodiscus (Peck) Halling from North America. It has shorter and wider, obovoid to ellipsoid basidiospores (χ m = 7.5±0.3 × 4.4±0.1 μm) with the Q m ratio close to 1.7 ( Desjardin 1989, personal observations of TENN 59556, TENN 49976, TENN 063109). The stipe of M. nigrodiscus is longer, not broadened towards base, pruinose only at apex and silky-striate below; the hyphae of the stipe surface and caulocystidia are not incrusted ( Halling 1983, TENN 59556, TENN 49976, TENN 063109). In the resulting ITS phylogenetic tree, all studied specimens of M. nigrodiscus form one well-supported clade (ML bootstrap = 100 %) clearly separated from M. macrocystidiosus (Fig. 4). The genetic distance between the sequences of these two species amounts to 12 %.

Another species, also considered as a variety of M. nigrodiscus ( Desjardin 1989) , Marasmius lilacinitinctus Mešić & Tkalčec , differs in the darker colour of the basidiocarps with distinct lilac tints, the smaller ellipsoid to obovoid or lacrimoid basidiospores (6.5–8 × 4–5 μm), and the wider (45–60 × 13–23 μm) saccate to broadly clavate cheilocystidia ( Halling 1983). Marasmius brunneospermus Har. Takah. , from East Asia, possesses a unique brown spore print, smaller basidiospores (χ m = 7.4 × 3.4 μm) as well as shorter (up to 75 μm) pleurocystidia ( Antonín et al. 2010a). It occupies a sister position to M. macrocystidiosus on the ITS tree with limited statistical support (Fig. 4). The pairwise base differences between their sequences is high (9.5 %). Marasmius notandus Corner from Borneo is distinguished from M. macrocystidiosus by the absence of clamps as well as a darker pileus, cheilo- and pleurocystidia with a short or long tip and large caulocystidia with a filiform tip ( Corner 1996). Other species with collybioid basidiocarps such as M. cystidiosus (A.H. Sm. & Hesler) Gilliam , M. goossensiae Beeli and M. fusicystidiosus Antonín, R. Ryoo & H.D. Shin differ in having glabrous, polished stipes without caulocystidia ( Singer 1964, Desjardin 1989, Antonín et al. 2010a). These species also have smaller, non-reniform basidiospores as well as shorter pleurocystidia. Marasmius oreades (Bolton) Fr. is somewhat similar in appearance but has clavate to cylindrical caulocystidia and can be easily distinguished from the new species by its lack of hymenial cystidia and large basidiospores ( Antonín & Noordeloos 2010).

The phylogenetic analysis (Fig. 4) showed that the ITS sequence of Marasmius macrocystidiosus matched one sequence of a specimen identified as M. albimyceliosus Corner (GenBank no. HF546218 ), obtained during a project on molecular characterization and identification of gilled fungi from Himalayan moist temperate forests in Pakistan (Razaq et al., unpubl. data). The pairwise base differences (genetic distance) between both sequences was only 0.9%, indicating their high similarity. However, according to the observed morphological features, our specimen cannot belong to M. albimyceliosus ( Corner 1996, Wannathes et al. 2009b). It differs from M. albimyceliosus by having more robust collybioid basidiocarps with a non-striate pileus margin, non-intervenose lamellae and a twisted pruinose stipe, larger basidiospores (χ m = 8.1±1.0 × 3.7±0.3 µm vs. χ m = 6.8±0.5 × 4.0±0.3 µm) and a different Q ratio (2.1 vs. 1.7), as well as the presence of conspicuous large pleurocystidia with yellowish refractive content. In addition, our ITS sequence differs strongly from another sequence of M. albimyceliosus (GenBank EU935544 ) generated by N. Wannathes and co-authors ( Wannathes et al. 2009b) from Northern Thailand material. Unfortunately we did not have the opportunity to examine any specimens of M. albimyceliosus , but N. Wannathes and co-authors have given a detailed description of their specimens ( Wannathes et al. 2009b), which absolutely corresponds to Corner’s point of view ( Corner 1996). Therefore it is more likely that the Pakistan specimen and our collection belong to a different and previously unknown taxon which is described herein.

FIGURE. Microscopic features of Marasmius macrocystidiosus sp. nov. (LE 295996). A. Spores. B. Cheilocystidia. C. Pleurocystidia. D. Elements of pileus surface. E. Caulocystidia.―Scale bar = 10 μm.

FIGURE. Best tree from the ML analyses of the nrITS data set for Marasmius . Bootstrap support values (ML/MP) are given above the branches. Thick branches designate clades having PP>0.95 (Bayesian posterior probabilities calculated for 2,500,000 generations). All tips are labelled with taxon name, GenBank accession number and country of the specimen’s origin.

Figures

FIGURE 2. Mature basidiocarps. A. Marasmius macrocystidiosus sp. nov. (LE 295996). B–C. Marasmius insolitus sp. nov. (LE 289497). D. Marasmius cohaerens var. mandshuricus var. nov. (LE 295987). E. Marasmius cf. ochroleucus (LE 295978). F. Cryptomarasmius aucubae (LE 289499). G. Marasmius occultatiformis (LE 295976). Scale bar = 1 cm.