Leucocoprinus mantadiaensis Ralaiv., Liimat., Niskanen sp. nov.

Index Fungorum number: IF 902404; Mycobank number: MB 902404; Facesoffungi number: FoF 16065; Fig. 1a–g

Etymology – The species epithet is derived from the name of the protected area “Mantadia” where the type specimen was collected.

Holotype – K-M 000251856

Pileus 1.5 cm in diam., convex to plano-convex, with an umbo in the centre, white, brown at the centre and very finely brown squamulose on the other parts. Lamellae free, crowded, white. Stipe 4 cm, white, cylindrical, with an annulus. Odour indistinct. Basidiospores 7–9(–10)×(3.5–)4–5 µm, amygdaloid to ellipsoid, without a germ pore, smooth, hyaline in KOH, strongly dextrinoid in Melzer’s. Basidia 17.5–22.5×8–9 µm, sterigmata 2.5–4 µm long, clavate, 4-spored, rarely 2-spored, not clamped. Cheilocystidia 14–42×9–15 µm, clavate. Pileipellis cutis, hyphae 3–6 µm wide, not clamped.

Habitat – Humid, tropical, evergreen primary forest with no disturbance, on organic soil. Dominated by Cunnoniaceae, Eugenia, Euphorbiaceae, Rubiaceae, Clusiaceae, Phyllanthaceae.

Distribution – So far only known from Madagascar.

Material examined – Madagascar. Toamasina, Andasibe, Mantadia Nature Reserve, tropical humid forest, 24 Feb. 2018, Robert Patrick Brown 000251856 (K-M, holotype), MAF18-231.

GenBank numbers – OR785983

Notes – Leucocoprinus mantadiaensis is placed, but without support, in a big group containing the type species of Leucocoprinus in our phylogenetic analysis. In addition, it does not belong to the well-supported Leucoagaricus s. stricto group with the type species of the genus Leucoagaricus. Therefore, we currently place the species in Leucocoprinus. Leucocoprinus mantadiaensis is a small, white species with a non-plicate pileus and a brown pileus centre. The spores are amygdaloid to ellipsoid 7–9(–10)×(3.5–)4–5 µm and the cheilocystidia are clavate 14–42 × 9–15 µm. ITS sequence (GenBank OR785983, holotype) is distinct from other members of Leucoagaricus/Leucocoprinus group and deviating from the other species (Leucoagaricus infuscatus GenBank no. EU141943, Lepiota flammeotincta GenBank no. OM474006, Leucocoprinus sp GenBank no. OL653095, and Leucoagaricus viriditinctus GenBank EU419375, AF482873) placed in the same well-supported (BS 99%) clade by more than 5%. The species is currently only known from Madagascar.

Figure 1 – Leucocoprinus mantadiaensis (K-M000251856, holotype). a Basidioma. b Basidiospores in Melzer’s. c Basidiospores in Congo red. d Basidiospores in KOH. e Basidia in Congo red. f Cystidia in Congo red. g Pileipellis in Melzer’s. Photographs Robert Patrick Brown, Anna Ralaiveloarisoa. Scale bar: a=1 cm; b–g=10 µm