Protohydnum livescens (Bres.) Spirin & V. Malysheva, 2025

Spirin, Viacheslav, Malysheva, Vera, Viner, Ilya, Alvarenga, Renato Lúcio Mendes, Grebenc, Tine, Gruhn, Gérald, Savchenko, Anton, Grootmyers, Django, Ryvarden, Leif, Vlasák, Josef, Larsson, Karl-Henrik & Nilsson, R. Henrik, 2025, Additions to the taxonomy of the Auriculariales (Basidiomycota) with pedunculate basidia, MycoKeys 120, pp. 339-392 : 339-392

Protohydnum livescens (Bres.) Spirin & V. Malysheva comb. nov.

Figs 6 F , 10 B , 11 H

≡ Sebacina livescens Bres. , Fungi Tridentini 2 (11–13): 64, 1898. Lectotype (selected here, MBT 10025862 ). Italy. Trentino-Alto Adige: Trento, Andalo , Abies alba (rotten log), VIII.1896 Bresadola ( S F 29132 , studied) .

= Exidiopsis livescens (Bres.) Bourdot & Maire , Bulletin de la Société Mycologique de France 36: 71, 1920.

= Sebacina laccata Bourdot & Galzin , Bulletin de la Société Mycologique de France 39: 262, 1924. Lectotype (selected by Hauerslev 1993). France. Aveyron: Millau, L’Hospitalet-du-Larzac , Pinus sp. , 25.IV.1910 Galzin 5743 (herb. Bourdot 7199) ( PC, studied).

Description.

Basidiocarps effused, covering a few cm, smooth or indistinctly tuberculate, gelatinous, first semitranslucent, whitish-greyish or cream-coloured, then greyish- to reddish-brown, opalescent, 0.02–1 mm thick, in dry condition almost invisible or turning to a vinaceous-brown vernicose crust, margin rather sharply delimited, adnate. Hyphal structure monomitic, hyphae hyaline or yellowish, clamped; subicular hyphae thin- to slightly thick-walled, interwoven or subparallel, frequently anastomosing, 2–4 μm in diam., subhymenial hyphae thin- to slightly thick-walled, interwoven or ascending, rather densely arranged and partly glued together, 1–3.5 μm in diam. Cystidia absent. Hyphidia abundant, richly branched, 0.5–2 μm in diam. at the apex, usually forming a continuous layer up to 20 μm thick. Basidia four-celled, longitudinally or rarely obliquely septate, ovoid-ellipsoid, pedunculate, (13 –) 14–20 (– 22) × (9.7 –) 9.8–14.3 (– 14.5) μm (n = 72 / 7), stalk up to 15 × 2–4 μm, sometimes strongly reduced, sterigmata tubular, gradually tapering, up to 20 × 2–3.5 μm. Basidiospores smooth, thin-walled, cylindrical to broadly cylindrical, often slightly curved, (9.1 –) 9.2–15.8 (– 15.9) × (4.7 –) 5.0–7.2 (– 7.3) μm (n = 240 / 8), L = 11.34–13.65, W = 5.71–6.46, Q’ = (1.6 –) 1.7–2.6 (– 2.8), Q = 1.85–2.23.

Distribution and ecology.

Europe ( Austria, France, Greece, Italy, Romania, Slovenia, Spain, and Ukraine); rotten decorticated wood of conifers ( Abies , Pinus ).

Remarks.

The species was originally introduced as a member of Sebacina accompanied by a peculiar conidial stage, Dendrodochium livescens Bres. ( Bresadola 1898). The authentic material is currently stored in two parcels in Stockholm. We studied them both and concluded that these specimens belong to two different species. The Dendrodochium stage is certainly an asexual ( Leucogloea ) stage of a Helicogloea species (cf. Kirschner 2004, Spirin et al. 2018 b); we will address its identity on a separate occasion. The teleomorphic fungus does represent a genuine member of the Auriculariales with four-celled, petiolate basidia, and it is evidently conspecific with Exidiopsis laccata Bourdot & Galzin . According to DNA data, S. livescens belongs to Protohydnum , and it is most closely related to P. erumpens from Africa and two neotropical species, P. cartilagineum (the generic type of Protohydnum ) and P. ocellatum described below. The lack of gloeocystidia and longer basidiospores differentiate P. livescens from P. galzinii , another representative of the genus in central and southern parts of Europe. The lectotype of S. laccata described from southern France ( Bourdot and Galzin 1924) is morphologically indistinguishable from the type of S. livescens and other specimens studied by us; S. laccata is therefore treated here as a synonym of P. livescens .

Neuhoff (1936) misapplied the name S. livescens to another species, which is distributed in northern Eurasia. The correct name for the latter taxon is Exidiopsis succinea K. Wells & Raitviir (see description in Wells and Raitviir 1987). It differs from P. livescens in having sessile (not pedunculate) basidia, larger basidiospores, and it occurs on angiosperms, preferably on wood of Salicaceae . Phylogenetically, these species are not closely related (Fig. 1 ). All previous records of E. livescens from northern Europe seem to refer to E. succinea .

Figures

Figure 1. Bayesian majority-rule consensus ITS + LSU-based tree of the Auriculariales overlaid with bootstrap support values from the maximum likelihood analysis. Support values are given as Bayesian posterior probabilities / ML bootstrap percentages. Species with stalked basidia are marked with a red X. I – Protohydnum clade; II – Elmerina clade; III – Hydrophana clade; IV – Endoperplexa – Mycostilla clade; V – Protoacia – Gelacantha clade; VI – Protomerulius clade; VII – Myxarium clade. The Sebacinales (Ditangium P. Karst., Sebacina, and Serendipita P. Roberts spp.) and Exidiopsis gloeophora were used as outgroups.

Figure 6. Basidiocarps of: A. Hydrophana trichiesiana (holotype); B. Mycostilla chromatica (holotype); C. Myxarium guianense (holotype); D. Protoacia reliqua (holotype); E. Protohydnum erumpens (holotype); F. P. livescens (specimen Spirin 15619); G. Protomerulius amiliavi (holotype); H. P. deceptorius (specimen Spirin 16784). Scale bar: 1 cm.

Figure 10. Microscopic structures of: A. Protohydnum lactescens (specimen TAAM 192048) (hymenial cells and tramal hyphae); B. P. livescens (specimen Spirin 13913) (hymenial cells and subhymenial hyphae); C. P. pallidum (holotype) (gloeocystidia and a basidium); D. P. sucinum (lectotype) (1 – basidia and basidiospores; 2 – gloeocystidia). Scale bar: 10 µm.

Figure 11. Basidiospores of: A. Protohydnum album (specimen Miettinen 196583); B. P. aureum (holotype); C. P. elasticum (holotype); D. P. elevatum (holotype); E. P. erumpens (holotype); F. P. galzinii (three left – specimen Miettinen 15900.4, three right – lectotype of S. galzinii); G. P. lactescens (four left – specimen TAAM 192048, three right – holotype of S. lactescens); H. P. livescens (specimen Spirin 13913); I. P. microperum (holotype); J. P. nudum (holotype); K. P. ocellatum (holotype); L. P. pallidum (holotype); M. P. pululahuanum (three left – lectotype, three right – specimen FH 00783538); N. P. sucinum (three left – lectotype of A. brasiliensis, three right – specimen BPI 701268); O. Protomerulius amiliavi (holotype); P. P. deceptorius (holotype). Scale bar: 10 µm.