Exidiopsis Vuillemin
Abstract
Exidiopsis (Bref.) Vuillemin, Bulletin des Séances de la Société des Sciences de Nancy 2 (3): 30, 1890 ≡ Exidia subgen. Exidiopsis Bref., Untersuchungen aus dem Gesammtgebiete der Mykologie 7: 94, 1888. Description. Basidiomata annual, effused, waxy-gelatinous, watery-grayish, often with pink or lilac hues. Hymenial surface smooth or spinulose. Hyphal structure monomitic; hyphae clamped, hyaline, gelatinized and often agglutinated, basidia-bearing hyphae usually well-differentiated. Crystals rare or usually absent. Cystidia absent. Hyphidia present, not encrusted, at least partly covering basidial cells. Basidia four-celled, ellipsoid-ovoid, sessile, thin-walled, usually embedded, often with a distinct stalk-like base. Basidiospores thin-walled, cylindrical or allantoid, distinctly curved. On dead wood of angiosperms. Generic type. Exidia effusa Bref. Our data show that the generic type of Exidiopsis, E. effusa, is not closely related to any other previously described Exidiopsis species. Instead, it is sister to Heteroradulum (Figs 1, 2; see Results) and, probably, Heterochaete s. typi (Malysheva and Spirin 2017); however, their phylogenetic relationships must be investigated further, with a much larger taxon sampling than used in the present study. In the current scope, the genus contains two species, E. effusa and E. perflua, introduced below. These two species differ from other species previously assigned to Exidiopsis in having pale and thin, waxy-gelatinous basidiomata, usually with a pink or lilac hue, ellipsoid-ovoid basidia with a clearly tapering base, long and curved basidiospores, as well as in lacking cystidia and distinctive encrustation. The taxonomic history of the genus is complicated. Exidiopsis was first introduced by Brefeld (1888) as a subgenus of Exidia for a single species, Exidia effusa. However, the species name was given in his text as ‘ Exidiopsis effusa ’, and this naming became the source of subsequent controversy. Donk (1958) correctly cited Brefeld’s binomial as Exidia effusa and considered it as validly published. However, he changed his mind eight years later (Donk 1966) and cited Brefeld’s species as Exidiopsis effusa Bref. ‘ n. v. p. ’ (= not validly published). The reasons for this later interpretation were not provided. Most likely, Donk switched to a more literal interpretation of Brefeld’s description and considered Exidiopsis effusa as a new species described by Brefeld without introducing the appropriate genus for it, i. e. as invalid. This viewpoint was accepted by Index Fungorum and MycoBank (as of December 1 st, 2025), both listing Brefeld’s binomial as the invalidly published Exidiopsis effusa. However, Brefeld’s explanations in the protologue of Exidiopsis effusa clearly show that he found no grounds to raise Exidiopsis to the genus rank and even argued against this option (Brefeld 1888: 94–95). It is therefore evident that Brefeld ascribed his new species to Exidia and merely followed the fashion of the time in using subgenera along with generic names in the species descriptions. Hence, Exidia effusa. Vuillemin (1890: 30) was the first author who used the name Exidiopsis at the genus level. He introduced a new species under the name Exidiopsis quercina and compared it with ‘ Exidiopsis effusa Bref. ’ By using the latter binomial, Vuillemin in fact created a new combination, Exidiopsis effusa (Bref.) Vuillemin, as was already noted by Donk (1958). Donk (ibid.) further stated that the new species E. quercina and the new combination E. effusa were not validly published by Vuillemin because he ‘ did not mention separately’ the generic name, i. e. Exidiopsis, at its new rank. However, this is not necessary under the current version of the Code: the indication ‘ Exidiopsis effusa Bref. ’ in Vuillemin’s description constitutes an indirect reference not only to Exidia effusa Bref. (Art. 38.14) but also to Exidiopsis as a validly published subgenus of Exidia (Art. 41.3). In other words, Vuillemin simultaneously combined Exidia effusa in Exidiopsis and raised the latter name to genus rank, thus fulfilling the requirements of Art. 41.2. Therefore, the generic name must be cited as Exidiopsis (Bref.) Vuillemin, while Exidiopsis (Bref.) Möller is merely its later isonym.
Authors 13
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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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Komarov Botanical Institute of the Russian Academy of Sciences
Affiliation as printed
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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Affiliation as printed
Société Linnéenne de Lyon, 33 rue Bossuet, 69006 Lyon, France
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Affiliation as printed
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
Affiliation as printed
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
Affiliation as printed
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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