Tricholosporum madagascariense Ralaiv., Liimat. & Niskanen, in Cao et al., Fungal Diversity 132: 522 (2025)

Index Fungorum number: IF 903128; MycoBank number: MB 903128; Facesoffungi number: FoF 17108; Figs. 1, 2

Etymology – This is the first Tricholosporum described from Madagascar.

Holotype – K-M 252063.

Pileus 3–5.5 cm in diam., at first convex, then very low convex, later almost plane and slightly depressed in the center, at first purple then becoming pale brown in the center, surface smooth, dry, waxy, not hygrophanous. Lamellae adnate, edge even, crowded with lamellulae, at first very pale to pale purple, turning pale brown when bruised. Stipe 2.5–3.5 cm long, up to 1.5 cm wide, whitish purple, swollen at base, mycelium white. Context not recorded. Odor and Taste not recorded.

Basidiospores 3.5–5.5 × 2.5–5 µm, cruciform to stauriform, thin-walled, hyaline in Melzer’s reagent. Basidia 19–27 × 5–6.5 µm, sterigmata 1–2 µm long, clavate, (2-)4-spored, clamped or not. Cheilocystidia and Pleurocystidia similar, 16–25.5 × 9.5–12.5 µm, clavate, thin-walled, with gray-violet to brownish green pigment, sometimes with an acute apex. Pileipellis cutis with parallel, irregular, non-septate hyphae, 4 µm wide, pale lime-green to yellow-olive in color.

Habitat – Dry, deciduous, tropical forest, on sandy soil.

Distribution – So far only known from Madagascar.

Material examined – MADAGASCAR, Mahajanga, Ankarafantsika National Park, tropical dry forest, dominated by Euphorbiaceae, Rubiaceae, Malvaceae, Celastraceae, Ebenaceae, 14 Feb 2017, coll. Shannon Skarha, MAF17-121 (K-M 252063, holotype). Mahajanga, Ankarafantsika National Park, tropical dry forest, 14 Feb 2017, coll. Melinda, MAF17-113 (K-M 1434141).

GenBank – K-M 252063: PQ636521 (ITS); K-M 1434141: PQ636522 (ITS).

Notes – The generic limits of Tricholosporum and Asproinocybe have not been fully resolved. The phylogenetic analysis of Mou and Bau (2021) showed that the genus Tricholosporum forms a well-supported clade whereas Asproinocybe is non-monophyletic. Our species belongs to a group (BS 86%) with other species of Tricholosporum. In addition, it has the typical basidiospores of the genus, whereas the spores of Asproinocybe are tuberculate to stellate. Therefore, we place our species in the genus Tricholosporum. ITS sequences (GenBank PQ636521, holotype; GenBank PQ636522): the two sequences are identical and group with low support (69% BS) with species Tricholosporum cossonianum (MW367843) from Italy and Tricholosporum sp. (OM022094) from USA and deviate from them by more than 5% (> 40 substitutions and indels). The Malagasy species belongs to the group of species with small spores, usually under 6 µm in length, subgroup of species with pigmented hymenial cystidia, which are gray-violet or brownish but differs from the other members of the group, which occur in the other continents, by having smallest cystidia.

Figure 1 – Tricholosporum madagascariense (K-M252063, holotype). a Basidiomata. b Basidiospores. c Basidia. d Pileipellis. Scale bars: a = 1 cm, b–d = 10 µm. Credit: Shannon Skarha (a), Anna Ralaiveloarisoa (b–d).

Figure 2 – The best scoring RAxML tree with a final likelihood value of -3861.641074 of the genus Tricholosporum and Asproinocybe based on the ITS region. Related sequences were retrieved from GenBank. Twenty-three specimens were included in the analysis of the ITS region which comprises 811 characters after alignment. The tree is rooted with Entoloma costatum (LN850578) and Entoloma sericeum (KF897025). The matrix had 418 distinct alignment patterns, with 20,26% of undetermined characters or gaps. Estimated base frequencies were: A = 0.267154, C = 0.184148, G = 0.191398, T = 0.357300; substitution rates AC = 0.961632, AG = 2.682519, AT = 1.405174, CG = 0.340012, CT = 2.939152, GT = 1.000000. Maximum Likelihood bootstrap values greater than 50% are given near to each branch. The type specimens are in bold. The new species are in blue. Names, other than those originating from the type specimens, are only indicative and not confirmed via comparison with sequences from type specimens.