Exidia plumbescens Spirin 2026, comb. nov.
Abstract
Exidia plumbescens (Burt) Spirin comb. nov. Figs 19 I, 20 D ≡ Sebacina plumbescens Burt, Annals of the Missouri Botanical Garden 3: 241, 1916 (nomen novum for S. plumbea Burt). = Sebacina plumbea Burt, Annals of the Missouri Botanical Garden 2: 765, 1915 (nom. illeg., non S. plumbea Bres. & Torrend). Holotype. USA. Washington: Klickitat Co., Bingen, Populus trichocarpa (fallen decorticated log), 18 Nov 1902, Suksdorf 862 (H – isotype, studied). = Sebacina burtii Trotter, Sylloge Fungorum 23: 573, 1925. = Exidiopsis plumbescens (Burt) K. Wells, Lloydia 20: 53, 1957. = Exidiopsis succinea K. Wells & Raitv., Transactions of the British Mycological Society 89: 341, 1987. Holotype. Russia. Krasnoyarsk Reg.: Yenisseysk Dist., Yartsevo, Salix fragilis, 10 Aug 1958, Parmasto (TAAM 7008 *, studied). Description. Basidiomata annual, effused, up to 10 cm in the widest dimension, gelatinous, opalescent, 0.5–1.5 mm thick. Hymenial surface smooth or indistinctly tuberculate, grayish to pale ochraceous in fresh condition, sometimes with reddish hues, corneous and amber-yellow to reddish-brown in herbarium; mineral inclusions abundant, white, first small and visible only under lens, in senescent basidiomata prominent and easily detectable. Margin rather clearly delimited, adnate, gradually thinning, concolourous with hymenial surface. Hyphal structure monomitic, hyphae clamped; subicular hyphae hyaline, thin-walled or with variably thickened, gelatinized walls, tightly interwoven or subparallel, anastomosing, 1.5–4 μm in diam., subhymenial hyphae hyaline, thin-walled, predominantly ascending, tightly arranged, 1.5–3.5 μm in diam., occasionally inflated up to 6 μm in diam., basidia-bearing hyphae well-differentiated, 3–5 μm in diam., occasionally showing a zigzag-like branching pattern. Crystals present as large, rosette-like agglomerations, up to 25 μm in diam. Hyphidia richly branched, with a hyphoid or subfusiform stem, 15–35 × 5–7.5 μm, and hyaline apical branches, 1–1.5 μm in diam., partly covering basidia. Probasidia broadly clavate to subglobose, 10–18 × 6–10.5 μm. Basidia four-celled, ellipsoid-ovoid, more rarely subglobose, sessile, occasionally slightly tapering to the base, (14 –) 15–22 (– 23) × (10.0 –) 10.3–17.4 (– 18.0) μm (n = 70 / 7), thin- or slightly thick-walled, exposed or embedded, in older hymenium often surrounded by gelatinous substance, sterigmata up to 35 × 2.5–3 μm. Basidiospores thin-walled, narrowly to broadly cylindrical, often distinctly curved, (11.7 –) 12.1–19.4 (– 20.2) × (4.3 –) 4.5–7.8 (– 8.0) μm (n = 240 / 8), L = 14.11–16.17, W = 5.19–6.62, Q = 2.21–3.13. Remarks. This species was first described as Sebacina plumbea based on a single specimen from the US North-West (Burt 1915). Burt’s name turned out to be a younger homonym of S. plumbea described by Bresadola and Torrend two years earlier (see above, under synonyms of D. thuretiana). Consequently, it was validated by Burt (1916) as S. plumbescens. Trotter (Saccardo and Trotter 1925) also reintroduced S. plumbea under a new name, Sebacina burtii. However, it must be rejected as a homotypic synonym of S. plumbescens. This species was accepted by Wells (1957) as a member of Exidiopsis and combined therein. A few years later, Wells (1961) included E. plumbescens in his broadly interpreted E. grisea and then resurrected it as a good species again (Wells and Wong 1985). We studied type material of both S. plumbescens and Exidiopsis succinea described from Siberia (Wells and Raitviir 1987) and concluded that they are conspecific. DNA data place S. plumbescens in the redefined Exidia (Figs 1, 2). Exidia plumbescens is widely distributed in the northern hemisphere although it is not common. In boreal forests, it occurs on dead branches and stems of Salix spp., more rarely on Populus spp. In more southern areas, it may inhabit other angiosperm trees (Fagus and Ulmus). Wells and Wong (1985) gave a long list of substrates for Exidiopsis plumbescens from the North American Pacific coast. It is, however, not clear to us whether all these records refer to Exidia plumbescens sensu typi. Exidia plumbescens is one of four entirely effused Exidia s. str. species dealt with in this paper. Of them, E. delita, differs from E. plumbescens in having thinner basidiomata, narrower hyphidia and on average smaller basidia and basidiospores (see above). Two other European species, E. repleta and E. saturata, differ from E. plumbescens in having thicker basidiomata covered by easily removable, whitish-grayish deposit. Both mentioned species possess a distinct epihymenial layer and they have cystidia. Moreover, hyphae of E. plumbescens are more or less evenly outlined while they are often clearly inflated in E. repleta and E. saturata. Exidia plumbescens can also be confused with effused forms of Descidia thuretiana. The easiest way to distinguish between them is to check the basidiome margin: it is always adnate, gradually thinning in E. plumbescens and elevated, often partly detaching from the substrate in D. thuretiana. Spirin et al. (2025) showed that earlier records of Exidiopsis livescens from North Europe belong to Exidiopsis succinea (Exidia plumbescens here). Previous reports and descriptions of Exidiopsis griseobrunnea from Norway (Torkelsen 1972; Hansen and Knudsen 1997) also refer to E. plumbescens.
Authors 13
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University of Helsinki · Finnish Museum of Natural History
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Finnish Museum of Natural History, University of Helsinki, PO Box 7, 00014 Helsinki, Finland
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Komarov Botanical Institute of the Russian Academy of Sciences
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Komarov Botanical Institute, Prof. Popova str. 2, 197022 St. Petersburg, Russia
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Affiliation as printed
Organismic Botany and Mycology, Institute of Plant Science and Microbiology, Ohnhorststraße 18, 22609 Hamburg, Germany
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Affiliation as printed
Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, Netherlands
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Société Linnéenne de Lyon, 33 rue Bossuet, 69006 Lyon, France
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Österplana Skattegården 2, 53384 Hällekis, Sweden
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Affiliation as printed
Globe Institute, Department of Biology, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen Ø, Denmark
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Affiliation as printed
Institute of Biological Sciences, University of Oslo, P. O. Box 1045, Blindern, N- 0316 Oslo, Norway
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University of Tennessee at Knoxville
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Department of Ecology and Evolutionary Biology, University of Tennessee, 1406 Circle Drive, Knoxville, Tennessee 37996, USA
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Affiliation as printed
Ecology and Genetics Research Unit, University of Oulu, P. O. Box 3000, FI- 90014 Oulu, Finland
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Czech Academy of Sciences, Biology Centre
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Biology Centre, Academy of Sciences of the Czech Republic, Branišovská 31, CZ 37005, České Budějovice, Czech Republic
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National University of Misiones
Affiliation as printed
Instituto de Biotecnología Misiones (InBioMis), Facultad de Ciencias Exactas, Químicas y Naturales, Universidad Nacional de Misiones, Ruta Nacional N 12, km 7.5, Posadas, Misiones, CP 3304, Argentina & Instituto Misionero de Biodiversidad (IMiBio), Ruta Nacional N 12, km 5, Puerto Iguazú, Misiones, CP 3370, Argentina
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University of Helsinki · Finnish Museum of Natural History
Affiliation as printed
Finnish Museum of Natural History, University of Helsinki, PO Box 7, 00014 Helsinki, Finland
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