Fomes inzengae (Ces. & De Not.) Cooke, Grevillea 14 (69): 18 (1885).
Basionym: Polyporus inzengae Ces. & De Not., Erb. critt. Ital., ser. 1: no. 636 [typeset description on label with specimen] (1861).
Type: Italy: Sicilia: Palermo, on Populus dilatata, 1860–1861, Inzenga [det. Cesati & De Notaris, Erb. critt. Ital., ser. 1 no. 636 [intermixed with “Mycotheca Universalis”] (SIENA – lectotypus hic designatus; IF556590); Prov. Siena: Radicondoli, Riserva Naturale Cornocchia, on living Quercus cerris, 26 Oct. 2016, U. Peintner & C. Perini (IB20160342, epitypus hic designatus; IF556625).
Diagnosis: Basidiomes macroscopically very similar to F. fomentarius from which it can be differentiated by the following characters: the pluriannual basidiomes have a hymenophore with 32–40 pores / cm; and the basidiospores are (9.0–) 10–12 (− 12.5) x (2.8–) 3.0–3.5 (− 3.8), Q = (2.8–) 3.0–3.6 (− 3.7) μm.
Description: Basidiomes perennial, sessile, ungulate, tough, woody, to 20 cm wide. Upper surface quickly developing a glabrous crust, grey (92LM) with a few dirty olivaceous spots (NP69), dull. Greyish coloured upper part the basidiome crust often conspicuously and irregularly marbled or brown-dotted. Marginal growth zone consisting of a distinctly zoned layer, zones 0.5–3 mm wide, in different shades of reddish brown (PR55), brown (NP67–69) or ochraceous brown (M70–71), minutely tomentose; transitional zone between ochraceous brownish zonate margin and grey older crust sometimes conspicuous and darker brown. Pore surface concave, pale brown, pores circular, 31–34 (− 38) pores / cm, with thick tomentose dissepiments. Tube layers indistinctly stratified, brown (PR59) and becoming stuffed; context tissue layer between the surface crust and the tubular layers, reddish brown (PR45), tough, azonate. Granular core developing at the upper part of the context, next to the substrate. Basidiospores cylindric, hyaline, smooth, not amyloid, (9.0) 10–12 (− 12.5) x (2.8–) 3.0–3.5 (− 3.8) μm, Q = (2.8-) 3.0–3.6 (− 3.7); n = 37; a large proportion germinate immediately. Basidia not observed. Cystidia not observed. Hyphal system trimitic, generative hyphae hyaline, thin-walled, with clamp connections, inconspicuous, 1.5–3.5 μm diam; Contextual skeletal hyphae thick-walled, non-septate, walls yellowish brown in KOH (3%), 3.2–6.9 μm diam, binding hyphae thick-walled, strongly branched, non-septate, 4.0–6.3 μm diam.
Cultures: Colonies reaching 4–6 cm diam after 5 d at 32 °C on 2% MEA; mycelium at first white, the cream to orange pinkish buff, reverse cream to orange, with felty to cottony consistency and fluffy surface structure. Generative hyphae with clamp connections, skeletal and binding hyphae readily formed, diam. of skeletal hyphae 1.3–3.5 μm, thick-walled, wall with yellow-ochraceous pigment. Inflated intercalary and terminal elements readily formed at temperatures of 32 °C and higher.
Habitat and distribution: On trunks of Quercus cerris, Q. pubescens, Castanea sativa, Carpinus betulus, Platanus acerifolia, and Populus spp., exceptionally also Cerasium avium and Abies alba. Based on sequences deposited in public databases, it occurs in Italy, Slovakia, Slovenia, Switzerland, United Kingdom, France, China and Iran. It is likely to be present through the whole Mediterranean area on suitable hosts, but is often misidentified as F. fomentarius (cfr, distribution of F. fomentarius shown in Bernicchia 2005).
Nomenclature: Fomes inzengae has long been regarded as a synonym or form of F. fomentarius (Bondartsev 1953; Domański et al. 1967; Donk 1933, 1974; Lécuru et al. 2019; Pilát 1941; Saccardo 1881). The basionym Polyporus inzengae is based on material collected and documented by Giuseppe Inzenga, who sent his material to De Notaris for identification. Cesati and De Notaris published the name with a printed description as no. 636 (see Fig. 10) in Erbario Crittogamico Italiano (Società crittogamologica italiana 1861; Sayre 1969), basing the description on the notes later reworked and twice published by Inzenga (1865, 1866) himself. Inzenga collected P. inzengae from Populus dilatata (now P. nigra) in Palermo (Italy, Sicily). The description from the protologue and description and illustrations from Inzenga’s Funghi Siciliani in black and white (Inzenga 1865: 17, pl. 2 Fig. 1) and reproduced in colour (Inzenga 1866: pl. 7 Fig. 1), agree with our concept of the Mediterranean Fomes lineage. Donk (1933) believed this was a milky white form of F. fomentarius, and others in the 20th century followed.
The original basidiome collected by Inzenga was cut into slices and sent to various herbaria as parts of an exsiccatae set. One part of this original collection no. 636 was later inserted in another set, the Mycotheca Universalis, conserved in Herbarium Universitatis Senensis (SIENA). This collection is interpreted as a syntype (cf. Wetzel and Williams 2018) and is here selected as the lectotype for the name; all other parts deposited elsewhere are therefore now isolectotypes. Cooke (1885b) transferred the name to Fomes in a list that was a continuation of Fomes species started in a previously published fascicle (Cooke 1885a) and is considered to have done so validly (Turland et al. 2018: Art. 35.1 Ex. 5).
The lectotype of Fomes inzengae is damaged by insects, but important diagnostic characters can still be evaluated: the hymenophore has 33–40 pores / cm, and the diameter of the skeletal hyphae ranges from (3.4–) 4.5–7.8 (− 10.0) μm (n = 30) with a mean value of 6.2 μm. A second collection of F. inzengae (Erb. critt. Ital. no. 977) collected in 1871 on Quercus (San Giuliano dal Sanno, Prov. Campobasso, Italy) has 32–38 pores / cm in the hymenium, and the skeletal hyphae range from 5.9 to 8.3 (− 9.4) μm. Unfortunately, we could not amplify DNA from these original collections of Fomes inzengae, and therefore we designate an epitype to fix the application of the name. Piccone (1876) recorded additional information on the second collection by Pedicino noting that it had also been included in Rabenhorst’s (1872) Fungi Europaei exsiccati no. 1508, which also consists of slices. Pedicino (1876) went on to record further observations.
Comments: Fomes inzengae has considerably smaller basidiospores than F. fomentarius. However, spores are difficult to observe in many pluriannual polypores because they are formed either in small quantities or during special, restricted seasonal periods. Additional characters, which are always present, are therefore crucial to distinguish these taxa: Fomes inzengae basidiomes can be separated from those of F. fomentarius on hymenophore pore size, and the diameter of skeletal hyphae. Moreover, substrate, growth rates, and volatile metabolites as well as pure culture characteristics help to distinguish these sister taxa. Barcoding rDNA ITS sequences are informative for species distinction in Fomes.
Additional specimens examined: Italy: Prov. Siena: Radicondoli, Riserva Naturale Cornocchia, on living tree of Quercus cerris, 29 Oct. 2013, M. N. D’Aguanno (IB20130333); loc. cit., on Q. cerris, 26 Oct. 2016, C. Perini, R. Kuhnert-Finkernagel & U. Peintner (IB20160343); loc. cit., on living tree of Q. cerris, 1 Dec. 2017, C. Perini (IB20170300); Monticiano Riserva Naturale di Tocchi, on Castanea sativa, 28 Oct. 2016, C. Perini, R. Kuhnert-Finkernagel & U. Peintner (IB20160349); loc. cit., on dead deciduous tree, 28 Oct. 2016, C. Perini, R. Kuhnert-Finkernagel & U. Peintner (IB20160350); loc. cit., on Carpinus betulus, 28 Oct. 2016, C. Perini, R. Kuhnert-Finkernagel & U. Peintner (IB20160351); loc. cit., on Quercus cerris, 14 Jan. 2017, C. Perini (MSIENA8138); loc. cit., on living tree of Quercus pubescens, 14 Jan. 2017, C. Perini (MSIENA8062). Prov. Campobasso: San Giuliano dal Sanno, on Quercus, Sep.1871, N. Pedicino (SIENA, Mycotheca Univ., Erb. critt. Ital. no. 977).
Fomes fomentarius (L.) Fr., Summa veg. Scand. 2: 321 (1849); nom. sanct. Syst. mycol. 1: 374 (1821)
Basionym: Boletus fomentarius L., Sp. Pl. 2: 1176 (1753).
(Figs 4, 11)
Type: Bulliard, Herb. Fr. tab. 491 fig. II C–F (1791, sub Boletus ungulatus Bull. (lectotypus hic designatus IF556624) (Fig. 11). Austria: Tirol: Innsbruck, Magdeburger Hütte, alt. 1300 m, on living Fagus sylvatica, 20 Jul. 2013, K. Rosam & U. Peintner, (IB20130019, epitypus hic designatus, IF556623; GenBank KM360127 (ITS)).
Diagnosis: Fomes fomentarius basidiomes usually form on Fagus or Betula in boreal or temperate habitats. The pluriannual basidiomes have hymenophores with 27–30 pores / cm; the basidiospores are 12–18 × 4–7 μm.
Description: Basidiomes perennial, sessile, ungulate, tough, woody, to 25 cm wide. Upper surface quickly developing a glabrous greyish crust. Margin light brown, minutely tomentose; pore surface concave, pale brown, pores circular, 27–30 pores / cm, with thick tomentose dissepiments. Tube layers indistinctly stratified, reddish brown and becoming filled; context tissue a layer between the surface crust and the tubular layers, yellowish brown, tough, azonate. Granular core developing at the upper part of the context next to the substrate. Basidiospores cylindrical, hyaline, smooth, not amyloid, (12.5–) 13.5–18 (− 20.5) × 4.5–6.5 (− 7.5) μm, Q = (2.5–) 3.0–3.6 (− 3.5); n = 480. Usually produced in the spring in large quantities, difficult to observe during the rest of the year. Hyphal system trimitic, skeletal hyphae thick-walled, non-septate, with yellowish brown wall in 3% KOH, 3.0–6.4 μm diam, binding hyphae thick-walled, strongly branched.
Pure cultures: Colonies reaching 2–4 cm diam after 5 d at 32 °C, mycelium first white, the cream to orange-pinkish buff, reverse cream to orange, with a velutinous-felty to cottony consistency. Generative hyphae with clamp connections, skeletal and binding hyphae readily formed, skeletal hyphae 1.5–3.7 μm diam, thick-walled, wall with yellow-ochraceous pigment. Inflated intercalary and terminal elements formed at temperatures > 32 °C.
Habitat and distribution: In temperate habitats associated with Fagus sylvatica, and Betula spp., occasionally also with Picea abies, Acer negundo, Populus sp. or Alnus incana. Widely distributed in northern and central Europe, including Latvia and Russia. In Russia also on Quercus. The records from Russia and Alaska (Betula neoalaskana) indicate a potential circumpolar distribution. Occurring also in southern Europe on Fagus.
Comments: Fomes fomentarius s. str. is a temperate species with distinct morphological characters and host preference for Fagus and Betula, but in Russia it also grows on Populus and Quercus. The original diagnosis of Linné (1753) refers to a polypore growing on Betula. Fries (1821), in the sanctioning work, described the fungus as growing on Fagus. He also mentioned its use as tinder and as remedy against bleeding: “pro fomite aptissima. In haemeragiis laudatus”. He also cited several illustrations, which can be used to select a lectotype as under Art. F.3.9 material cited in the protologue of a sanctioning work is treated as original material for the purposes of lectotypification. The illustration published by Bulliard (1791) was selected as lectotype here as it best represents the current concept of Fomes fomentarius. Moreover, it is easily available online (https://doi.org/10.5962/bhl.title.5365). A epitype is designated here in order to precisely fix the application of the name. We selected a collection from Austria on Fagus as epitype because all data are available for this collection, including a pure culture.
Additional specimens examined: Austria: Tirol, Achenkirch, Christlum, on Fagus, 26 Aug. 1991, U. Peintner (IB19910934); loc. cit., on Fagus, 21 May 2017, U. Peintner (IB20170012); Gnadenwald, Gunggl, towards Maria Larch, on Fagus, 1 May 1991, U. Peintner (IB19910047); Innsbruck, Hötting, alt. 817 m, on Fagus, 10 Jul. 2013, K. Rosam & U. Peintner (IB20130011, IB20130016); loc. cit., Stangensteig, alt. 820 m, on Picea, 25 Sep. 2013, K. Rosam & U. Peintner (IB20130022); Kärnten, Eberstein, on Fagus sylvatica, 13 Jun. 1990, U. Peintner (IB19901036). – Finland: Utsjoki, Kevo, Kevojokki, on dead Betula, 18 Aug. 1998, M. Moser (IB19980038). Sweden, Småland, Femsjö, Hägnan, Fagus, 21 Aug. 1976, M. Moser, IB19760143. – Italy: Corleto Monforte, Salerno, Parco Nazionale del Cilento e Vallo di Diano, 12 May 2008, Pecoraro (MSIENA8156); loc. cit., 12 May 2008, Pecoraro (MSIENA8157); loc. cit., 12 Nov. 2014, M. N. D’Aguanno (IB20140121). – Russia: Moskow Oblast: on Betula, 18 Oct. 2014, A. Shiryaev (SVER 926310); Sverdlovsk Oblast, Ekaterinburg City, on Betula, 4 Oct. 1978, N.T. Stepanova-Kartavenko (SVER 49614); loc. cit., Populus, 4 Aug. 1973, A. Sirko (SVER 10032); Orenburg Oblast, Orenburg State Nature Reserve, Populus, 1 Oct. 2017, A.G. Shiryaev (SVER 926313); Volgograd Oblast, Volzhsky, Populus, 8 Oct. 2001, A.G. Shiryaev (SVER 420865); Novgorod Oblast, Ilmen, Populus, 18 Aug. 1973, N.T. Stepanova-Kartavenko (SVER 229302); Smolensk Oblast, Dneper valley, Populus, 26 Sep. 2016, A.G. Shiryaev (SVER 867100); loc. cit., Vyazma, Quercus robur, 22. Aug. 1978, V. Ipolitov (SVER 155532); Samara Oblast, Zhiguli Nature Park, Q. robur, 10 Sep. 1983, F. Igorev (SVER 303495); Bashkiria: on Betula, 18 Aug. 1963, N.T. Stepanova-Kartavenko (SVER 19051); loc. cit., Nature Park Bashkiria, Q. robur, 19 Aug. 2012, A.G. Shiryaev (SVER 926313); Krasnodar Krai, on Betula, 5 Oct 1975, N.T. Stepanova-Kartavenko (SVER 22302); Perm Krai, Solikamsk, Populus, 23 Sep. 1999, A.G. Shiryaev (SVER 72466); Kabardino-Balkar Republic, Q. robur, 27 Sep. 2006, A.G. Shiryaev (SVER 784532); Karelia Republic, Kivach Nature Reserve, Betula, 20 Sep. 2017, A.G. Shiryaev (SVER 926311); Tatarstan Repubic, Betula, 30 Sep. 1971, A. Sirko (SVER 38225).