Marasmius tangerinus Wannathes, N. Suwannarach, J. Kumla & Lumyong, sp. nov.
Index Fungorum number: IF 840380; MycoBank number: MB 840380; Facesoffungi number: FoF 10683; Fig. 1
Etymology – tangerinus’=tangerine colour, refers to the pileus colour
Holotype – BKF10249
Pileus 2–3 mm diam., hemispherical to convex, umbilicate, with a tiny dark brown papilla at center; dull, dry, glabrous, striate; orange red (8A8) overall when young, orange red (8A8) at disc, orange (6B7) to tangerine (6B8) at margin in age. Context thin, white. Lamellae adnate to a small collarium, distant (10–11), narrow (0.5 mm), pale orange (5A3), marginate with orange. Stipe 13–20×0.3 mm, cylindrical, central, glabrous, dull, dry, insititious, golden brown (5D7) overall, sometimes stipe arising directly from golden brown rhizomorph.
Basidiospores 8–10 × ( 4 – ) 4 . 5 – 5 µm [x=8.56±0.71×4.92±0.28, Q=1.6–2.0, q=1.74±0.16, n=25] ellipsoid, fusoid, smooth, hyaline, inamyloid, thin-walled. Basidia 16–18×6–8 µm, clavate, with 4 sterigmata, thin-walled, inamyloid. Cheilocystidia abundant, of Siccus- type broom cells; main body 10–14×5–7 µm, cylindrical to clavate, sometime branched, hyaline, inamyloid, thin-walled; apical setulae 1–4 ×1(–2) µm, cylindrical to conical, obtuse, pale yellow, thin- to thick-walled. Pleurocystidia absent. Pileipellis hymeniform, not mottled, composed of 2 type of cells: (a) Siccus-type broom cells; main body 18–38×10–16 µm, clavate to broadly clavate or turbinate, irregular in outline, hyaline to pale yellow, inamyloid, thin- to thick-walled; apical setulae 2–10×1–4 µm, cylindrical to conical, regular in outline, obtuse, yellow to pale brown, inamyloid, thick-walled; (b) non-setulose cell, 8–32 × 10–15 µm, clavate to broadly clavate, sometime branched, yellow to pale brown, inamyloid, thick-walled. Pileus trama interwoven, inamyloid. Lamellar trama interwoven, hyphae 4–8 µm diam., cylindrical, inflated, smooth, hyaline, inamyloid, thin-walled, non-gelatinous. Stipitipellis subparallel, hyphae 4–6 µm diam., cylindrical, pale brown, smooth, dextrinoid, thick-walled (up to 1 µm), nongelatinous. Stipe trama subparallel, hyphae 2–4 µm diam., cylindrical, hyaline, smooth, dextrinoid, thin-walled, nongelatinous. Caulocystidia absent. Clamp connections present in almost all tissues.
Material examined – Thailand, Nakhon Ratchasima Provinve, Khao Yai National Park, 33 km marker on Hyw 2090, 22 Sep 2018, collectors N Wannathes, N Suwannarach J Kumla, S Lumyong, BKF10249 (holotype), NW1224 (isotype).
Habit, habitat and known distribution – Gregarious on dicotyledonous wood, known only from Thailand.
GenBank numbers – MZ452087 (ITS).
Notes – Marasmius tangerinus is characterized by a tiny, hemispherical, bright orange pileus, with dark brown papilla at the center, collariate, distant lamellae, thin stipe, sometimes arising directly from the rhizomorph, ellipsoid to fusoid basidiospores with mean 8.6×4.9 µm, pileipellis composed of mixed Siccus type broom cell and non-setulost cells, with the presence of cheilocytidia, and ligicolous habit. Marasmius tangerinus is morphologically similar to M. trichorhizus Speg. which has been characterized from a neotropic realm. The latter species differ by forming more lamellae (12–15), longer stipe (4–71 mm long), and smaller basidiospores with mean 6.9×3.4 µm (Oliveira 2020). The phylogenetic analyses of the ITS sequence data (Fig. 2)
indicate that M. tangerinus is a distinct species from other related morphological species and other taxa within this genus.
Figure 1 – Marasmius tangerinus BKF10249 (holotype). a Basidiomata, b Basidiospores, c Basidium, d Checlocystidia, e Pileipellis cell. Scale bars: a=5 mm, b–e=10 μm. Photographs and drawing by N. Wannathes
Figure 2 – Phylogenetic tree derived from maximum likelihood analysis of a combined ITS gene of 65 sequences and the aligned dataset was comprised of 1116 characters including gap. The average standard deviation of the split frequencies of the BI analysis was 0.00825. Marasmius siccus KG 039 and KG 119 were used as outgroup. Numbers above branches are the bootstrap statistics percentages (left) and Bayesian posterior probabilities (right). Branches with bootstrap values ≥70% are shown at each branch and the bar represents 0.1 substitutions per nucleotide position. Hyphen (-) represents support values ≤70%/0.95. Extype strains are in black bold. The newly generated sequences are indicated in blue and bold type species