Protohydnum erumpens A. Savchenko & Spirin, 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 erumpens A. Savchenko & Spirin sp. nov.

Figs 6 E , 11 E

Holotype.

Kenya. Taita-Taveta: Taita Hills, Ngangao Forest , Xymalos monospora (fallen branch), 23.XI.2017 Savchenko 171123 / 1515 * ( H 7008774 ).

Etymology.

Erumpens (Lat., present participle of ‘erumpo’) – erumpent, in reference to the basidiocarp’s growth.

Description.

Basidiocarps effused, up to 3 cm in widest dimension, erumpent, smooth, gelatinous, semitranslucent, bluish-greyish to pale ochraceous, 0.04–0.1 mm thick, in dry condition almost invisible, margin gradually thinning-out. Hyphal structure monomitic, hyphae hyaline or yellowish, clamped; subicular hyphae slightly thick-walled, subparallel, frequently anastomosing, 2–3 μm in diam., subhymenial hyphae thin- to slightly thick-walled, interwoven or ascending, rather loosely arranged, 2–4 μm in diam. Cystidia absent. Hyphidia abundant, richly branched, 0.5–1 μm in diam. at the apex, occasionally forming a continuous layer up to 15 μm thick. Basidia four-celled, longitudinally septate, ovoid-ellipsoid, pedunculate, (12 –) 13–16.5 (– 17) × (9.0 –) 9.2–11.2 (– 11.3) μm (n = 20 / 1), stalk up to 14 × 3–4.5 μm, sometimes strongly reduced, sterigmata gradually tapering, up to 20 × 2–3 μm. Basidiospores smooth, thin-walled, cylindrical to broadly cylindrical, slightly to moderately curved, (8.9 –) 9.3–12.3 (– 13.4) × (5.0 –) 5.1–6.4 (– 6.8) μm (n = 30 / 1), L = 11.12, W = 5.78, Q’ = (1.6 –) 1.7–2.2 (– 2.3), Q = 1.93.

Distribution and ecology.

Africa ( Kenya); partly corticated fallen angiosperm branch.

Remarks.

Morphologically and phylogenetically, P. erumpens is closest to P. livescens (Fig. 1 ). It differs from this species in having thinner basidiocarps, shorter basidia, and slightly smaller basidiospores. Protohydnum erumpens is so far known only from the type locality in Africa, where it was collected from angiosperm wood remnants. In turn, the European species P. livescens seems to be restricted to coniferous hosts.

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 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.