Phlegmacium fennicum Kekki, Kytöv., Niskanen & Liimat., sp. nov.

Index Fungorum number: IF 900310; Mycobank number: MB 900310; Facesoffungi number: FoF 14867; Figs. 1a, 2a, 3

Etymology – The species has thus far only been found from Finland.

Holotype – K-M 001434119.

Pileus 4.5–7 cm in diam, at first hemispherical, then low convex to almost plane, yellowish brown with brown fibrils, with hygrophanous streaks. Lamellae subcrowded, pale brown to pale greyish brown when young, brown when old. Stipe 6–8 cm long, 1–1.5 cm thick at the apex, up to 3 cm at base, bulbous with a somewhat marginate to more rarely rounded bulb, at first very pale yellowish brown, later pale yellowish brown, fibrillose. Context pale yellowish brown. Universal veil pale brown, at the margin of the bulb. Mycelium white. Odour indistinct. Taste somewhat bitter. KOH reaction in pileus, in the context of bulb and in bulbipellis negative. Basidiospores (8.5–)9–10(–10.5)×5–6(–6.5) µm, amygdaloid-citriform to citriform, coarsely verrucose. ITS sequence (GenBank ON843423, ex holotype) distinct from other members of Phlegmacium and with 92% similarity to the closest known species.

Habitat and distribution – In Picea abies forest on calcareous ground and so far known only from Finland.

Material examined – Finland, Perä-Pohjanmaa, Keminmaa, Kallinkangas, W part, herb-rich Picea abies forest on calcareous ground, 28 June 2015, T. Kekki 1774, 215553 (TUR). loc. cit., 25 June 2019, T. Kekki 3657, 001434119 (holotype in K-M; isotype in OULU).

GenBank numbers – TK1774: ITS=ON843434; TK3657: ITS=ON843423.

Notes – Phlegmacium fennicum is a precocious species producing basidiomes already in June. It can be recognized by the combination of yellowish brown basidiomes without bluish tints, amygdaloid-citriform to citriform, coarsely verrucose basidiospores and habitat with Picea on calcareous ground. It belongs to the P. subgenus Bulbopodium sect.
Arcifolia. The two other known species of the section, P. arcifolium and P. subhygrophanum, occur with Fagus in Europe.

Figure 1 – Basidiomes of the species of the genera Phlegmacium and Thaxterogaster. a Phlegmacium fennicum (K-M 001434119, holotype). b Phlegmacium pallidocaeruleum (K-M 001434120, holotype). c Thaxterogaster americanoporphyropus (K-M 001434121, holotype). d Thaxterogaster obscurovibratilis (K-M 001434124, holotype). Photographs: a Tapio Kekki, b–d Kare Liimatainen

Figure 2 – Basidiomes of the species of the genera Phlegmacium and Thaxterogaster. a Phlegmacium fennicum (K-M 001434119, holotype). b Phlegmacium pallidocaeruleum (K-M 001434120, holotype). c Thaxterogaster americanoporphyropus (K-M 001434121, holotype). d Thaxterogaster obscurovibratilis (K-M 001434124, holotype). Drawings: Tuula Niskanen. Scale bars: 10 µm

Figure 3 – The best scoring RAxML tree of the genera Phlegmacium and Thaxterogaster based on the ITS region. Related sequences were retrieved from GenBank. Twenty-six specimens were included in the analysis of the ITS region which comprises 671 characters after alignment. The tree is rooted with Thaxterogaster. Estimated base frequencies were: A=0.246332, C=0.202234, G=0.200934, T=0.350500; substitution rates AC=1.534815, AG=3.904253, AT=1.485681, CG=0.452034, CT=6.187457, GT=1.000000, gamma distribution shape parameter α=0.257017. Maximum likelihood bootstrap values higher than 50% are given at the nodes. The holotype specimens retrieved from the GenBank are in bold and black. The new species are in bold and blue. The section of the species is indicated after the collection/GenBank no. of each specimen