Hygrocybe mitsinjoensis Ralaiv., Liimat., A.M. Ainsw., Niskanen sp. nov.
Index Fungorum number: IF 902406; Mycobank number: MB 902406; Facesoffungi number: FoF 16067; Figs. 1c, 2b, 3b, 4b
Etymology – The name is derived from the type locality “Mitsinjo Forest” of the species.
Holotype – K-M000251832
Pileus 0.5–1 cm in diam., convex, bright red, smooth. Lamellae adnate to adnexed or subdecurrent, subdistant, thick, white, becoming dark pink or red near the pileal attachment. Stipe 2.5–4.5 cm long, 1–2 mm thick at the apex, light red, becoming yellow towards the base, cylindrical. Odour not recorded. Basidiospores 7–8×4–5(–6) µm, somewhat ovoid to ellipsoid, smooth, hyaline in Melzer’s, monomorphic. Basidia (27.5)37–53×6–7(8.5) µm, sterigmata 3.5–7 µm long, clavate, (1-)4-spored, some clamped, monomorphic. Ratio of basidial to basidiospore length>5. Lamellar trama subregular. Pileipellis a cutis, some clamps seen, hyphae 3–5 µm wide. ITS sequences (GenBank OR785984, holotype): The three specimens studied here as well as a published sequence from UNITE (UDB015243/ SH1243293.09FU, Taolagnaro, Madagascar) form one clade with an intraspecific variation<0.5% and are distinct from other species of Hygrocybe. The sister species from Zambia and Gabon (UDB013832, GenBank no JQ657787) differs by 2.3% (15 indels and substitutions).
Habitat – Humid, tropical, Humid, tropical, evergreen primary forest with no disturbance, dominated by Eugenia, Sarcolaena, Rubiaceae, Fabaceae, Phyllantaceae, on organic soil. Distribution: So far only known from Madagascar.
Material examined – Madagascar. Toamasina, Andasibe, Mitsinjo Forest, tropical humid forest, 23 Feb 2018, T. Niskanen 000251832 (K-M, holotype), MAF18-193. Madagascar. Toamasina. Andasibe, Mitsinjo Forest, tropical humid forest, 23 Feb 2018, T. Niskanen 000251833 (K-M), MAF18-180. Madagascar. Toamasina. Foulpointe, Analalava Forest Reserve, tropical humid forest, 19 Feb 2017, L. Chen 000252098 (K-M), MAF17-242.
GenBank numbers – OR785984
Notes – The species can be identified by the combination of small basidiomata with the red pileus, two-coloured stipe that is pale red at the top and yellow towards the base, and ovoid to ellipsoid basidiospores (7–8×4–5(–6) µm). It belongs to Hygrocybe subgenus Pseudohygrocybe and has the typical characteristics of that subgenus: the mean ratio of basidial to basidiospore length is>5. In addition, the lamellar trama is subregular and the basidia and spores are monomorphic.
Figure 1 – Basidiomata of the Hygrocybe species: a Hygrocybe minimiholatra 000251949 (holotype, K-M), b Hygrocybe parviholatra 000251897 (holotype, K-M), c Hygrocybe mitsinjoensis 000251832 (holotype, K-M), d Hygrocybe solis 000251894 (holotype, K-M), e Hygrocybe solis 000252075 (K-M), f, g Hygrocybe vintsy 000252026 (K-M). Photographs a Javier Galan, b Paul Eguia, c Tuula Niskanen, d Paul Eguia, e Tuula Niskanen, f, g Meilinda Sulastri. Scale bar 1 cm
Figure 2 – Basidiospores Hygrocybe species in Melzer’s. a Hygrocybe minimiholatra (K-M000251949, holotype). b Hygrocybe mitsinjoensis (K-M000251832, holotype). c Hygrocybe parviholatra (K-M000251897, holotype). d Hygrocybe solis (K-M000251894, holotype). e Hygrocybe vintsy (K-M000252026, holotype). Photographs Anna Ralaiveloarisoa. Scale bar=10 µm
Figure 3 – Basidia of the species of the genus Hygrocybe in Melzer’s. a Hygrocybe minimiholatra (K-M000251949, holotype). b Hygrocybe mitsinjoensis (K-M000251832, holotype). c Hygrocybe parviholatra (K-M000251897, holotype). d Hygrocybe solis (K-M000251894, holotype). e Hygrocybe vintsy (K-M000252026, holotype). Photographs Anna Ralaiveloarisoa. Scale bar=10 µm
Figure 4 – Pileipellis of the species of the genus Hygrocybe in Melzer’s. a Hygrocybe minimiholatra (K-M000251949, holotype). b Hygrocybe mitsinjoensis (K-M000251832, holotype). c Hygrocybe parviholatra (K-M000251897, holotype). d Hygrocybe solis (K-M000252026, holotype). e Hygrocybe vintsy (K-M000251894, holotype). Photographs Anna Ralaiveloarisoa. Scale bar=10 µm