Exidia truncata Fr.
Abstract
Exidia truncata Fr., Systema Mycologicum 2: 224, 1822 Figs 23 H, 24 C Neotype (designated here, MBT 10031443). Sweden • Västergötland: Göteborg, Guldheden, Quercus robur (dead hanging branch), 28 Dec 2024, Spirin 18029 * (GB, duplicate – H). Description. Basidiomata annual, button-shaped or adpressed-orbicular, narrowly attached, rarely with a reduced stalk-like base up to 0.5 cm long, later turbinate or nearly cupulate, up to 5 cm in diam., up to 1.5 cm thick, gelatinous. Hymenial surface uneven or indistinctly folded, covered by rather regularly arranged spine-like black projections up to 0.2 mm long, dark gray to brownish-gray, later brownish-black, in dry condition completely black. Abhymenial surface rough, covered by densely arranged blackish dots or sharp outgrowths up to 0.1 mm long, grayish-brown. Margin free, concolourous with hymenial surface, entire, even or indistinctly lobate. Hyphal structure monomitic, hyphae clamped; context hyphae hyaline or rarely grayish, thin- to distinctly thick-walled, predominantly interwoven, anastomosing, 0.5–6 μm in diam., subhymenial hyphae hyaline to grayish or brownish, thin-walled or with a distinct wall, ascending or interwoven, 1.5–4 μm in diam., basidia-bearing hyphae 1.5–5 μm in diam. Hyphidia with a hyaline or grayish-brownish hyphoid stem, 1.5–8 μm in diam., and hyaline or pale grayish apical branches, 0.5–1 μm in diam., forming a continuous layer up to 50 μm thick. Probasidia tapering to subfusiform, 14–22 × 5–10.5 μm. Basidia four-celled, ellipsoid-ovoid, thin-walled, (14.5 –) 15–22 (– 23) × (9.1 –) 9.3–13.3 (– 13.7) μm (n = 30 / 3), sterigmata up to 50 × 1.5–2 μm. Basidiospores narrowly cylindrical to allantoid, distinctly to strongly curved (lunate), (13.0 –) 13.7–20.1 (– 20.4) × (4.3 –) 4.4–6.2 (– 6.3) μm (n = 90 / 3), L = 17.12–18.03, W = 4.89–5.06, Q = 3.44–3.57. Remarks. Exidia truncata was described by Fries (1822). However, its identity remained controversial, mainly because no original specimens or illustrations were extant. Neuhoff (1936 b) applied the name E. truncata to an Exidia with adpressed-orbicular or turbinate basidiomata occurring mainly on Quercus branches in temperate Europe. Our data show that Neuhoff’s concept of E. truncata covers two similar and closely related species. The first species has a hairy abhymenial surface, while it is minutely dotted or scabrose (covered by tiny, densely arranged sharp warts) in the second one. Moreover, the second species has longer basidiospores than the first one. The ongoing convention, including recent DNA studies, attributed the epithet E. truncata to the first species (Weiß and Oberwinkler 2001; Ye et al. 2020; Gruhn et al. 2024). However, this attribution is at odds with Fries’ concept of the species. He described E. truncata as ‘ subtus punctato-scabra’ (Fries 1822: 224) while all forms with a hairy abhymenial surface were addressed by him to E. glandulosa (ibid., ‘ subtus cinerea subtomentosa’). We therefore reintroduce the name E. truncata for the second of the two above-mentioned species; the first species is redescribed and typified above as E. glandulosa. Exidia truncata seems to be rather common in the south-western part of Sweden. The GenBank sequence KU 973844 from Tunisia belongs to this species, too. It means that the species is most likely widely distributed and just overlooked. Fries observed E. truncata growing in the winter, and this fits our observations. The basidiomata of E. truncata start developing in December and completely disappear by the end of April. In contrast, the similar E. glandulosa can be collected throughout the year, although it sporulates mainly in winter or early spring. All our records of E. truncata came from hanging or recently fallen branches of Quercus robur. Fries (1822) stated that he collected E. truncata from Tilia twigs. It is so far uncertain whether he misidentified the host tree or whether E. truncata can inhabit host trees other than Quercus. The third, equally possible option is that Fries’ concepts of both E. glandulosa and E. truncata were intertwining – a suggestion made by Donk (1966) and discussed above under E. glandulosa. Whichever the case is, it does not influence the neotype selection guided by the most reliable feature distinguishing the two species, namely the character of the abhymenial surface.
Authors 13
-
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
-
Komarov Botanical Institute of the Russian Academy of Sciences
Affiliation as printed
Komarov Botanical Institute, Prof. Popova str. 2, 197022 St. Petersburg, Russia
-
Affiliation as printed
Organismic Botany and Mycology, Institute of Plant Science and Microbiology, Ohnhorststraße 18, 22609 Hamburg, Germany
-
Affiliation as printed
Naturalis Biodiversity Center, Darwinweg 2, 2333 CR Leiden, Netherlands
-
Affiliation as printed
Société Linnéenne de Lyon, 33 rue Bossuet, 69006 Lyon, France
-
Affiliation as printed
Österplana Skattegården 2, 53384 Hällekis, Sweden
-
Affiliation as printed
Globe Institute, Department of Biology, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen Ø, Denmark
-
Affiliation as printed
Institute of Biological Sciences, University of Oslo, P. O. Box 1045, Blindern, N- 0316 Oslo, Norway
-
University of Tennessee at Knoxville
Affiliation as printed
Department of Ecology and Evolutionary Biology, University of Tennessee, 1406 Circle Drive, Knoxville, Tennessee 37996, USA
-
Affiliation as printed
Ecology and Genetics Research Unit, University of Oulu, P. O. Box 3000, FI- 90014 Oulu, Finland
-
Czech Academy of Sciences, Biology Centre
Affiliation as printed
Biology Centre, Academy of Sciences of the Czech Republic, Branišovská 31, CZ 37005, České Budějovice, Czech Republic
-
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
-
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
Cited by 0 stored of 0
No patents citing this paper on Lens.org (checked 2026-10-11).