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

Marasmius auranticapitatus J.S. Oliveira, sp. nov. (Figs 9A; 10) Differs from M. haematocephalus by having pale orange pileus and slightly larger basidiospores (xmm = 21.1 [± 0.7] × 3.8 [± 0.3] µm, Qmm = 5.7 [± 0.5] vs xmm = 20.5 [± 0.3] × 3.9 [± 0.2] µm, Qmm = 5.2 [± 0.1]); and more distinctly larger than those of the rose or pale red piliated M. rubicundus (xmm = 21.1 [± 0.7] × 3.8 [± 0.3] µm, Qmm = 5.7 [± 0.5] vs xmm = 18.9 [± 0.5] × 3.8 [± 0.1] µm, Qmm = 5 [± 0.2]). HOLOTYPE. — Brazil. São Paulo State, Santo André City, Reserva Biológica de Paranapiacaba, 2.XII.2009, M. Capelari & L.A.S. Ramos 4554 (holo-, SP[SP 445584]!). ADDITIONAL EXAMINED MATERIAL. — Brazil. São Paulo State, Santo André City, Reserva Biológica de Paranapiacaba, 16.III.2010, J.J.S. Oliveira JO42 (SP[SP 445408]!); 15.X.2010, J.J.S.Oliveira & C.L.A. Pires JO224 (SP[SP 445445]!); 16.X.2010, J.J.S. Oliveira & C.L.A. Pires JO226 (SP[SP 445446]!); 7.XI.2010, J.J.S.Oliveira & A. V. Costa JO276 (SP[SP 445460]!): J.J.S. Oliveira & A. V. Costa JO277 (SP[SP 445461]!); J.J.S. Oliveira & A. V. Costa JO279 (SP[SP 445463]!); 7.XII.2010, J.J.S. Oliveira, A. V. Costa & P.O. Ventura JO282 (SP[SP 445465]!); J.J.S. Oliveira & P.O. Ventura JO300 (SP[SP 445479]!). ETYMOLOGY. — Based on the orange pileus. MYCOBANK. — MB 842535. HABIT AND SUBSTRATE. — Marasmioid (Figs 9A; 10A), dispersed to gregarious on dead eudicotyledonous leaves in the forest litter. DESCRIPTION Pileus 2.4-19 mm diam.(Figs 9A; 10A), initially conical, then campanulate or hemispherical, sulcate, sometimes deeply sulcate, center flat or slightly umbonate, wrinkled when dried, margin decurved, edge entire; when young deep reddish orange (N 10 Y 80 M 30 to N 10 Y 99 M 60, N 40 Y 70 M 70), with center dark orange (N 10 Y 99 M 70), becoming yellowish orange or pale orange (N 00 Y 80 M 30, N 10 Y 99 M 50 to N 20 Y 60 M 50) when mature, sometimes with beige hue (N 00 Y 40-60 M 20-40 to N 10 Y 50 M 50-60) or ferruginous orange (N 20 Y 99 M 60) to reddish brown (N 20 Y 50 M 50) when dried, keeping the same pigmentation at the center or becoming chestnut orange (N 30 Y 99 M 50-70, N 40 Y 99 M 80 or N 50 Y 99 M 70); membranous, context thin (<1 mm); glabrous, dry, dull, subvelutinous, non-hygrophanous. Lamellae (Fig. 9A) Free, subfree to narrowly adnate, subdistant to distant, L = 9-14, equal, simple, rarely biforked or intervenose, l = 0, smooth, pale cream (N 00 Y 10 M 00), edge even, non-marginate, interlamellar hymenium concolorous with the lamellae faces. Stipe (Figs 9A; 10A) 9-56 × 0.3-0.8 mm, central, filiform, thin, equal, regular, with circular caliber, chitinous, flexible, hollow, apex whitish pink (N 00 Y M 20-60) to pale orange, becoming orange or amber brown (N 40 Y 60 M 50) to brown or dark brown (N 70 Y 99 M 60) toward the base, glabrous, smooth, with a silky bright; with a scarce, cream, tomentose basal mycelium. 10-40 Odor Not distinctive. Basidiospores (Fig. 10B) 17.1-24.8 × 2.8-5 µm (xrm = 19.4-22.3 × 3.5-4.2 µm; xmm = 21.1 [± 0.7] × 3.8 [± 0.3] µm; Qrm = 5.1-6.3; Qmm = 5.7 [± 0.5], n / s = 30/8), exceptional spore size of JO226 with 17-21.9 × 3-4.2(-5) µm (xm = 19.4 [± 1.0] × 3.6 [± 0.4] µm; Qm = 5.4 [± 0.7]; n / s = 30, s = 1), oblong, subclavate to fusoid, smooth, hyaline, thin-walled, inamyloid. Basidia Observed in JO279, 20.1-30.4 × 6-7.6 µm, clavate, hyaline, thin-walled, inamyloid, 4-sterigmate, sterigmata coarse or broad, with obtuse apex. Basidioles (Fig. 10C) 21.3-28.8 × 6-8.8 µm, clavate, hyaline, thin-walled, inamyloid. Pleurocystidia (Fig. 10D) (15.1-)22.3-74.3 × 5.2-12.1 µm, clavate, with tapered apex, subacuminate, vesiculose, capitate or papillate, sublageniform, hyaline, thin-walled, refractive. Cheilocystidia (Fig. 10E) Similar to the Siccus-type broom cells of the pileipellis; main body (10-)15-18.8 × 5.6-11.3 µm, clavate to turbinate, hyaline, thin-walled; setulae apical, erect, 2.5-7.5 × 0.8-1.8 µm, cylindrical, regular in outline, solid, apex acute. Lamellar trama Dextrinoid, irregular, interwoven, hyphae cylindrical, 1.6- 10 µm diam., regular in outline, branched, smooth, hyaline, thin-walled. Pileus trama Similar to the lamellar trama, hyphae 2-6.3 µm diam. Pileipellis Hymeniform, composed of Siccus-type broom cells (Fig. 10F), abundant, pale yellow when grouped; main body 9.4- 18.8 × 7-10.6 µm, clavate to frequently turbinate, sometimes inflated, or irregular in outline, hyaline,thin-walled, weakly dextrinoid; setulae apical, erect, 3.8-7.5 × 0.6-1.3 µm, filiform,thin, regular in outline, sometimes branched,solid,hyaline, apex acute. Stipe trama Dextrinoid, cortical hyphae parallel, 3-13.8 µm diam., cylindrical, regular in outline, rarely branched, smooth, pale brown, thick-walled; internal hyphae 2.5-7.5 µm diam., hyaline, thin-walled. Clamp connections Present in all tissues. REMARKS Marasmius auranticapitatus J.S. Oliveira, sp. nov. is very similar to M. haematocephalus (blood red pileus) but has more pale yellowish orange pileus (reddish when young) and slightly longer basidiospores (xmm = 21.1 [± 0.7] × 3.8 [± 0.3] µm, Qmm = 5.7 [± 0.5] vs xmm = 20.4 [± 0.3] × 3.9 [± 0.1] µm, Qmm = 5.3 [± 0.1]). Yet, the ranges of the basidiospores sizes are largely overlapping. Marasmius auranticapitatus J.S. Oliveira, sp. nov. is 0.2-1 % dissimilar to M. haematocephalus based on the nrITS and 0.6-1 % dissimilar on the nrLSU.However, M. auranticapitatus J.S. Oliveira, sp. nov. is closer and sister to M. rubicundus (Singer) J.S. Oliveira, stat. nov. (Figs4; 5). Based on the nrITS data, M. auranticapitatus J.S. Oliveira, sp. nov. is 0.7-1.7% dissimilar to M. rubicundus (Singer) J.S. Oliveira, stat. nov., 0.2-0.6 % dissimilar in the nrLSU, 4.7-5.2% dissimilar in the rpb 2 and 1.4-1.9 dissimilar in the ef 1 - α. Marasmius auranticapitatus J.S. Oliveira, sp. nov. differs from M. rubicundus (Singer) J.S. Oliveira, stat. nov. in the pale yellowish orange pileus (vs rose, pink or pale red) and longer basidiospores (xmm = 21.1 [± 0.7] × 3.8 [± 0.3] µm, Qmm = 5.7 [± 0.5] vs xmm = 18.9 [± 0.5] × 3.8 [± 0.1] µm, Qmm = 5 [± 0.2]). With a transitional/ intermediate pattern and possibly a hydrid, the exceptional spore sizes of JO226 (more compatible with M. rubicundus (Singer) J.S. Oliveira, stat. nov.) strengthens the plausibility of the most recent common ancestry between M. auranticapitatus J.S. Oliveira, sp. nov. and M. rubicundus (Singer) J.S. Oliveira, stat. nov., a bridge of intercompatibility and gene flow or an ancestry trace. QuotingTaylor et al. (2000): “Even when BSR (Biological Species Recognition) can be applied to fungi, there is evidence that the criterion of reproduction lumps together groups of fungi that are genetically isolated in nature, but that retain the ancestral character of interbreeding”. Marasmius auranticapitatus J.S. Oliveira, sp. nov. is similar to M. siccus in the pileus pigmentation. However, based on the holotype, M. siccus has smaller basidiospores 15.2- 20 × 3.2-4.6 µm (Desjardin 1989). Also, M. siccus s.l. has more robust basidiomata (Gilliam 1976; Noordeloos 1987; Antonín & Noordeloos 2010; Antonín et al. 2012;) and temperate distribution. In the phylogenetic trees (Fig. 1), M. auranticapitatus J.S. Oliveira, sp. nov. is close to M. haematocephalus (embedded in haemat_cp1) and distant from M. siccus. Marasmius auranticapitatus J.S. Oliveira, sp. nov. is part of the haemat_cp2a (Fig. 3), only fully resolved in Figure 5. Marasmius haematocephalus var. anomaloides Desjardin originally described from the Tennessee, United States, also has orange pileus but differs from M. auranticapitatus J.S. Oliveira, sp. nov. in having much shorter basidiospores (14.4-19.2 × 3.4-4.6µm) (Desjardin 1991). The new species is neighter similar to any of the varieties of M. haematocephalus in Singer (1976) nor to any of the heterotypic sysnonyms once listed under M. haematocephalus (Appendix).

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