Marasmius castanocephalus J. S. Oliveira 2022, sp. nov.

Marasmius castanocephalus J.S. Oliveira, sp. nov. (Figs 9B; 11) Differs from Marasmius davidii Antonín in having non-marginate lamellae, slightly smaller basidiospores (20-26 × 3-4 µm vs 20-27 × 4-6 µm), in having yellowish pleurocystidia, and in growing on dried leaves. HOLOTYPE. — Brazil. São Paulo State, Iporanga City, Parque Estadual Turístico do Alto Ribeira, 29.II.2012, J.J.S. Oliveira & D.E. Desjardin JO523 (holo-, SP[SP 445573]!). ETYMOLOGY. — From Greek Καστανός (kastanos) and ΚΕΦάλι (kephali), based on the brownish pileus. MYCOBANK. — MB 842536. HABIT AND SUBSTRATE. — Marasmioid (Figs 9B; 11A 1), close, on dried eudicotyledonous leaves in the forest litter. DESCRIPTION Pileus (Figs 9B; 11A 1) 7.5-15.7 mm diam., hemispheric to conical-campanulate, sulcate, center flat or slightly umbonate, margin decurved, edge entire to crenate; center to mid disc light chestnut to buff brown (N 50 Y 60-80 M 30-40), margin pale sepia brown (N 40 Y 40 M 30) to pale buff brown or brownish beige (N 20 Y 30 M 20 to N 10 Y 30- 40 M 10); membranous, context white, thin (<1 mm); glabrous, dry, dull, papyraceous to subvelutinous, non-hygrophanous. Lamellae (Fig. 11A 2) Free to adnexed, subclose to subdistant, L = 11-12, equal, narrow to slighty broad, simple, l = 0, opaque, smooth, pale cream (N 00 Y 10 M 00), edge even, non-marginate, interlamellar hymenium concolorous with the lamellae faces. Stipe (Figs 9B; 11A 1) 61-80 × 0.5-0.8 mm, central, filiform, thin, equal, with circular caliber, chitinous, tough, hollow, apex concolorous with the lamellae, amber (N 60 Y 50 M 30) to dark brown (N 90 Y 70-99 M 50), or almost black downwards, glabrous, smooth, with a silky bright; with a scarce, cream, tomentose basal mycelium. Odor Not distinctive. Basidiospores (Fig. 11B) 20-26 × 3-4 µm (xm = 22.6 [± 1.2] × 3.7 [± 0.3] µm, Qm = 6.1 [± 0.5], n / s = 32/1), oblong, clavate to subfusoid, smooth, hyaline, thin-walled, inamyloid. Basidia Not observed. Basidioles (Fig. 11C) (16.3-)20-25 × 5-8 µm, clavate, rarely tending to acuminate, smooth, hyaline, thin-walled, inamyloid. Pleurocystidia (Fig. 11D) 33-50 × 9.8-13.8 µm, abundant, broadly clavate, sometimes tapered towards the apex, some capitate, or with a small apical vesicle, or mucronate, smooth, refractive, with faint content, somewhat fuscous, yellowish, thin-walled, inamyloid. Cheilocystidia (Fig. 11E) Similar to the Siccus-type broom cells in the pileipellis, pale brown when grouped, main body 8-22.5 × 5-15 µm, clavate to slightly turbinate, or pyriform to almost globose, sometimes ventricose, thin-walled; setulae apical, erect, short to generally elongate, 2.5-8.8 × 0.6-1 µm, cylindrical, filiform, thin, rarely digitiform, regular in outline, simple, pale yellow to hyaline, solid, apex somewhat obtuse or more frequently acute. Lamellar trama Dextrinoid, irregular, interwoven, hyphae cylindrical, 2.5- 17.5 µm diam., regular or irregular in outline, branched, hyaline, smooth, thin-walled. Pileus trama Dextrinoid, irregular, hyphae interwoven, cylindrical, 1.3-8 µm diam., similar to the lamellar trama, but with some inflated hyphal segments. Pileipellis Hymeniform, composed of Siccus - type broom cells (Fig. 11F), abundant, yellowish to pale chestnut when grouped; main body 8.8-18.8 × 5.6-14 µm, clavate to turbinate, rarely globose or branched, hyaline, thin-walled; setulae apical, erect, 2-7.5 × 0.5-1.3 µm, cylindrical, thin, filiform, simple, regular in outline or contorted, yellowish, solid, apex acute or slightly obtuse. Stipe trama Dextrinoid, cortical hyphae parallel, cylindrical, 1.8- 8.8 µm diam., regular in outline, branched, brownish, smooth, thick-walled; internal hyphae hyaline, thin-walled, 2.5-8 µm diam. Clamp connections Present in all tissues, except in the cortical hyphae of the stipe. REMARKS Marasmius castanocephalus J.S. Oliveira, sp. nov. is mainly characterized by the buff brown to brownish beige pileus, the large basidiospores (20-26 × 3-4 µm) and somewhat fuscous to yellowish pleurocystidia (33-50 × 9.8-13.8 µm). It seems a member of stirps Helvolus (Singer 1976) in ser. Haematocephali (sensu Singer 1976) because of the brown pileus as in M. helvolus Berk. Marasmius castanocephalus J.S. Oliveira, sp. nov. is closer to M. davidii from Sri Lanka (Indo-Malayan realm), initially described as M. helvolus var. brunneolus Berk. & Broome (Berkeley & Broome 1873). Pegler (1986) elevated this variety to M. brunneolus (Berk. & Broome) Pegler. Marasmius helvolus has much smaller basidiospores (11-15 × 2.8-4 µm) and not projecting, inconstant, smaller (19-25 × 5-10.2 µm), opaque and thick-walled pleurocystidia (Singer 1976). Due to the homonym with M. brunneolus (Beeli) Singer, in sect. Globulares (traditional sense) (Singer 1964), Antonín (2003) replaced M. brunneolus (Berk. & Broome) Pegler with M. davidii. This species differs from M. castanocephalus J.S. Oliveira, sp. nov. mainly in having very distant, marginate lamellae (brown edge), slightly larger basidiospores (20-27 × 4-6 µm), only hyaline pleurocystidia and brownish cheilocystidia (setulae), and basidiomata found on dead sticks (Pegler 1986). Marasmius brunneolus var. fuliginosus Desjardin & E.Horak was described having dark brown to fuliginous pileus (Desjardin & Horak 1997). Marasmius castanocephalus J.S. Oliveira, sp. nov. is close to M. haematocephalus var. leucophyllus Singer, and to M. musicola Murrill, M. allocystis Singer, and M. oleiger Singer (stirps Oleiger) because of the brownish pigmentation of the pileus within ser. Haematocephali sensu Singer (Singer 1976). All these taxa, however, have much shorter basidiospores (up to 20.5 µm) and the last three have distinct pleurocystidia with oil-like content. No other formally published variety under M. haematocephalus seems close. Marasmius semipellucidus Berk. & Broome is discarted as conspecific with M. castanocephalus J.S. Oliveira, sp. nov. (Appendix) by the translucent stipe and geography of the original collection. In the phylogenetic trees(Figs1;3), M.castanocephalus J.S.Oliveira, sp. nov. appears close to M. roseus J.S. Oliveira, sp. nov., but with unsupported resolution. Both species branched in haemat_cp1. Marasmius castanocephalus J.S.Oliveira, sp.nov. is close to M. haematocephalus but is 4.4%dissimilar in nrITS and2.6%in nrLSU and differs by the pale brown pileus and larger basidiospores.

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