Thaxterogaster americanoporphyropus Niskanen, Liimat. & Ammirati, sp. nov.
Index Fungorum number: IF 900312; Mycobank number: MB 900312; Facesoffungi number: FoF 14869; Figs. 1c, 2c, 3
Etymology – The species is known from North America and is reminiscent of T. porphyropus.
Holotype – K-M 001434121.
Pileus 4–8 cm in diam, at first hemispherical, then low convex, pale silvery grey to ochraceous, viscid- sticky to glutinous. Lamellae medium spaced, at first purplish grey, pale brown with age, becoming strongly purple when touched. Stipe 5–8 cm long, 0.8–1.3 cm thick at the apex, up to 2 cm at the base, clavate, whitish grey, with more or less purplish tints, especially when young, becoming strongly purple when touched. Context completely purple or only in parts of the pileus, cortex and at the base of the stipe, and then other parts white. Universal veil white, sparse. Mycelium white. Odour at the base of the stipe honey-like. Basidiospores 8.5–9.5 × 5–6 µm, amygdaloid to obovoidly amygdaloidellipsoid, strongly verrucose. Basidia hyaline in 5% KOH. ITS sequence (GenBank ON843425, ex holotype) distinct from other members of T. subgen. Scauri sect. Purpurascentes and with 98.5% similarity to the closest known species, T. porphyropus and T. occidentalis.
Habitat and distribution – In mixed coniferous forests and so far known from North America: Alberta, British Columbia, Quebec and Washington.
Material examined – Canada, Alberta, Hinton, 5 September 2011, K. Liimatainen, T. Niskanen 11–392, 001434123 (K-M). USA, Washington, Mount Baker, Easy Pass trailhead, coniferous forest with Tsuga heterophylla, Abies and some Picea engelmannii, 28 September 2009, K. Liimatainen, T. Niskanen 09-020, 001434122 (K-M). Snohomish Co., Barlow past, Mount Baker-Snoqualmie national forest, mixed coniferous forest with mainly Tsuga heterophylla and some Pseudotsuga mentziesi and Abies amabilis, 3 October 2009, K. Liimatainen, T. Niskanen 09-042, 001434121 (holotype in K-M; isotype in H).
GenBank numbers – TN09-042: ITS=ON843425; TN09-020: ITS=ON843426; TN11-392: ITS=ON843427.
Notes – In the field the species looks like T. porphyropus and also their basidiospores are similar. Thus far, T. porphyropus is not known from the Western side of the Rocky Mountains and there the default identification would be T. americanoporphyropus. In the east side an ITS sequence is needed for unambiguous identification. The closely related C. occidentalis differs by having purple basidiomes and somewhat smaller (7–9×4.5–5.5 µm), slightly to moderately verrucose basidiospores.
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