Leucoagaricus madagascarensis Ralaiv., Liimat., Niskanen sp. nov.

Index Fungorum number: IF 902403; Mycobank number: MB 902403; Facesoffungi number: FoF 16064; Fig. 1a–g

Etymology – The species epithet is derived from the name of the country (Madagascar) from which the type specimen was collected.

Holotype – K-M 000251887

Pileus 5 cm in diam., at first low convex, then almost plane with a low and broad umbo; brownish pinkish orange, fibrillose-striate, black at the centre, background cream white. Lamellae free, crowded, white. Stipe 6.5 cm, white, clavate, annulus membraneous. Odour strong mushroom smell. Basidiospores (6–)6.5–9.5(–10)×3.5–5(–6.5) µm, amygdaloid to ellipsoid, without germ pore, smooth, hyaline in KOH, moderately dextrinoid in Melzer’s. Basidia (in Congo red) 12–15×6.5–9 µm, sterigmata 1.5–2.5 µm long, broadly clavate, usually 4-spored, rarely 2-spored, not clamped. Cheilocystidia (11.5–)22–50.5×(7.5–)10–2 0 µm, cylindrical to clavate. Pileipellis cutis, hyphae up to 3.5–6 µm wide, not clamped.

Habitat – Humid, tropical, evergreen primary forest with no disturbance, on organic soil.

Distribution – So far only known from Madagascar.

Material examined – Madagascar. Toamasina, Andasibe, Mantadia Nature Reserve, tropical humid forest, 25 Feb. 2018, P.A. Hagl 000251887 (K-M, holotype), MAF18-249 (TAN, isotype).

GenBank numbers – OR785982

Notes – Leucoagaricus madagascarensis groups with 100% bootstrap support with the type species of Leucoagaricus. The species is characterised by brownish pinkish orange, at the centre blackish pileus, membraneous annulus and amygdaloid to ellipsoid 6.5–9.5×3.5–5 µm basidiospores. ITS sequence is distinct from other species of Leucoagaricus s. str. and deviating from them by>3% (>20 substitutions and indels). It is the first Leucoagaricus species described from Madagascar and is currently not known to occur elsewhere.

Figure 1 – Leucoagaricus madagascarensis (K-M000251887, holotype). a Basidioma. b Basidiospores in Melzer’s. c Basidiospores in Congo red. d Basidiospores in KOH. e Basidia in Congo red. f Cystida in Melzer’s. g Pileipellis in Melzer’s. Photographs P.A. Hagl, Anna Ralaiveloarisoa. Scale bars: a=1 cm; b–g=10 µm