Castanoporus castaneus (Lloyd) Ryvarden

This monotypic genus contains one conifer-dwelling resupinate polypore species from East Asia. With its simple-septate hyphae, monomitic and dense structure (in basal layer) with thick-walled hyphae, middle-sized spores and subulate, encrusted cystidia the species brings into mind Phlebiopsis under the microscope. For a more detailed description see Nuñez and Ryvarden (2000).

Phylogenetically the species comes close to Phlebiopsis flavidoalba and P. pilatii. Together those three species form a sister clade to core Phlebiopsis, typified by P. gigantea (Figures 2 and 3). For now the most practical solution is to include Castanoporus in Phlebiopsis (see discussion under Phlebiopsis). Hjortstam (1987) listed Castanoporus castaneus under Phlebiopsis in his check-list of corticioid fungi, but made no formal combination. If Phlebiopsis would be defined more strictly, then Castanoporus could be put in use.

The genus Cystidiophorus has been described for Castanoporus castaneus, but for nomenclatural reasons described below we think Castanoporus should prevail against Cystidiophorus. Bondartsev and Ljubarsky (1963) described the monotypic genus Cystidiophorus with the species C. merulioideus as the type. Unfortunately, they did not indicate a type specimen for the species, which makes the species name invalid, and also rendered the genus invalid (Melbourne Code Art. 40; the cut-off year for type indication is 1958). Later, Imazeki (Imazeki and Hongo 1965) made the combination Cystidiophorus castaneus based on Merulius castaneus Lloyd, mentioning C. castaneus and C. merulioideus as synonyms. This combination does not qualify as a validation of Bondartsev and Ljubarsky’s genus name, because Imazeki did not provide reference to the genus description, which is clearly separate from the species description in the original paper (Art. 38.1). In such a case, the genus could be considered valid with the condition that no previously described species is mentioned (Art. 38.5a), but this is not the case as Imazeki mentions Lloyd’s species. Thus, we follow Ryvarden (1991) and regard Castanoporus as the correct name for this genus.

Ginns (1969) lectotypified C. castaneus and gave a description of the type, which agrees well with our concept of the species as well as that of Imazeki’s and Bondartsev’s. Also Maas Geesteranus (1974) studied the lectotype from BPI.

Zmitrovich et al. (2006) combined C. castaneus in Australohydnum. We do not have material of Australohydnum from Australia (the type locality of the type species) or any sequences, but judging from the type of cystidia and hyphal structure we think it is unlikely (but possible) that Australohydnum belongs to Phlebiopsis as delineated here (see Oxychaete for further notes on Australohydnum). If Phlebiopsis were to be split, Castanoporus and Australohydnum would probably both persist being morphologically quite distinct.

Hapalopilus nidulans (Fr.) P. Karst. (= H. rutilans (Pers.) Murrill)

Pileate to resupinate polypores with soft to cottony corky, ochre to pink basidiocarps. Hyphal structure monomitic, clamps always present, generative hyphae slightly thick-walled, 2–5.5 µm in diameter, CB−, IKI−, KOH−, covered with granular, golden yellow pigment that dissolves in KOH turning purple. Cystidia absent. Hymenial cells relatively long, 12–25×4.2–5.5 µm. Spores ellipsoid to subcylindrical, thin-walled, 3–5×2–3.2 µm.

Altogether 36 species have been combined to Hapalopilus, most of them bright-colored, soft polypores with a monomitic, clamped hyphal system. The genus type H. nidulans belongs to the Phanerochaetaceae as shown by us (Figure 2) and previous work (Binder et al. 2005, Binder et al. 2013, Floudas and Hibbett 2015). Other species traditionally referred to this genus (H. alborubescens, H. croceus, H. ochraceolateritius etc.) belong to other lineages of the Polyporales (Niemelä et al. 2012, Dvořák et al. 2014), and their phylogeny and taxonomy will be revisited on further occasion.

Here we include four species in Hapalopilus in the strict sense, three of which are new to the genus. According to our data, Hapalopilus rutilans is a holarctic species, H. eupatorii and H. ribicola are found in Europe, and H. percoctus is so far only known from the type locality in Botswana. These species are morphologically very similar, and thus Hapalopilus as a genus is morphologically easy to characterize. The purple KOH reaction of Hapalopilus is shared by its pigmented, corticioid relatives in Rhizochaete (Wu et al. 2010, Chikowski et al. 2016).

Unlike other Phanerochaetaceae polypore genera recognized here, Hapalopilus has a typical polypore subhymenium of sinuous, tightly packed, interwoven hyphae instead of the loose corymb type seen in Oxychaete, Phanerina, Phanerochaete and Riopa. Also Phlebiopsis species (including Castanoporus) have an interwoven subhymenium.

Morphological, ecological and geographic data of Hapalopilus species are summarized in Table 3.

H. eupatorii has completely resupinate, thin basidiocarps on dead herbaceous stems (Arctium, Eupatorium, and Reynoutria). It has been recorded once on thin fallen branches of Robinia in a thicket of Reynoutria. Karsten (1884) described the species from France as Physisporus eupatorii, but it long remained an enigma for mycologists (Lowe 1956, Donk 1974). Recently it was reported from England as Ceriporiopsis herbicola (Fortey and Ryvarden 2007) and Germany as H. nidulans f. resupinata (Dämmrich 2014).

Figure 5. 

Hapalopilus fruiting bodies, a Hapalopilus rutilans, Vlasák Jr. 0407/34-J b Hapalopilus eupatorii, Rivoire 5333.

Figure 6. 

Microscopic characters of Hapalopilus. Hapalopilus percoctus, holotype, a subicular hyphae b tramal hyphae c hymenium and subhymenium d hymenial cells. Spores of e Hapalopilus eupatorii, lectotype f Hapalopilus percoctus, holotype g Hapalopilus ribicola, lectotype h Hapalopilus rutilans, Niemelä 7134.

Botswana. Gaborone, Golf course, -24.652°: 25.936°, strip of natural bush, felled log or tree stump (40 cm in diameter), 28 May 2008, Reijo Miettinen (H 7008581).

Percoctus, parched, scorched; refers to the sun-exposed habitat of the species.

Similar to Hapalopilus rutilans with pileate basidiocarps. Microscopically otherwise identical, but H. percoctus has clearly wider spores and tramal hyphae (Table 3). The spore dimensions come close to H. eupatorii, which has larger pores, effused basidiocarps and grows usually on woody herbs. Its tramal hyphae are also narrower. Hapalopilus percoctus is the only species in the genus known to us from the Southern Hemisphere.

This species was described by Karsten (1881) based on the sole collection from Finland. It had usually been regarded as a form of H. rutilans (Lowe 1956). However, our data show that specimens growing on Ribes spp. in North Europe are distinct from H. rutilans and phylogenetically closer to H. eupatorii. All specimens of H. ribicola studied by us are from Finland, from branches of both wild and cultivated Ribes spp. The species is evidently widely distributed and just overlooked.

This common species has gone under two names, H. rutilans and H. nidulans. Many authors have chosen to use H. nidulans over H. rutilans, (Bondartsev 1953, Gilbertson and Ryvarden 1986, Bernicchia 2005, Ryvarden and Melo 2014), but also the latter name has been in use (Murrill 1904, Donk 1974, Niemelä 2005). Hapalopilus rutilans is an older name than H. nidulans, and since both were sanctioned by Fries, the former has priority (ICBN Melbourne code art. 15.4).

Neither of the names has been typified. Persoon’s original publication includes a rather uninformative painting of the fungus, probably Hapalopilus rutilans or Inonotussensu lato. The original description of H. nidulans is similarly scanty. No material suitable for lectotypification remains of either species, so we have chosen to designate neotypes for both species to fix the nomenclature: H. rutilans based on a French specimen from oak in accordance to the protologue (Persoon 1798) as Persoon got material mainly from Germany and France, and H. nidulans based on a Finnish specimen, since Fries (1821) based his description on his own collection from neighboring Sweden.

Ryvarden (1991) attempted to designate a lectotype for H. nidulans. We dispute his typification, since he used an illustration in Bulliard’s publication from 1791 as the type, whereas Fries’s original work does not refer to Bulliard. The fact that Fries later (1836-1838) referred to Bulliard doesn’t make the drawing available for lectotypification: only the original material is valid under the code (ICBN Melbourne art. 9.2, 9.12).

Oxychaete cervinogilva (Jungh.) Miettinen

Constructed from Oxyporus and Phanerochaete, but can be interpreted as “bearing sharp setae”.

Effused-reflexed polypores with yellow-brown colors, light cardboard-like consistency and large, shallow pores. Monomitic, simple-septate, with slightly thick-walled hyphae and abundant subulate, naked, thick-walled cystidia of subhymenial origin. Hymenial branching corymb-like. Spores curved cylindrical, large (6–8×3–3.5 µm).

Other hydnoid and poroid genera with simple-septate hyphae and encrusted, thick-walled cystidia include Australohydnum, Phlebiopsis, Flavodon and Irpex. The latter two are phylogenetically distantly related to Oxychaete, and they possess dimitic hyphal structure quite different from the loose monomitic structure of Oxychaete. Phlebiopsis is phylogenetically distinct from Oxychaete (Figure 2), and its hyphal structure is more compact, even agglutinated (basal layer). Hyphae are also winding and covered with abundant brownish encrustation, which is lacking in Oxychaete. Cystidia are tramal in origin (as opposed to hymenial in Oxychaete). Due to the hyphal structure the basidiocarp is tougher and not board-like when cut as in Oxychaete.

Australohydnum is a more difficult case to decide on since there are no good references on the microscopic characters of the type species, Hydnum griseofuscescens Reichardt from Australia. Descriptions vary so much that it is possible that many species and even genera have been recognized as Australohydnum dregeanum (Berk.) Hjortstam & Ryvarden and its supposed synonyms (Jülich 1978, Hjortstam and Ryvarden 1989, Gilbertson and Adaskaveg 1993, Melo and Hjortstam 2002, Zmitrovich et al. 2006). Sometimes the structure is monomitic, sometimes dimitic; cystidia may be subulate or obtuse; basidiocarps may be resupinate with smooth hymenophore or hydnoid with caps.

Reid (1955, 1963) refers directly to Australian material and the type, and provides an illustration (under Irpex vellereus). His A. griseofuscescens is a pileate, hydnoid species with violaceous brownish basidiocarps, very thick-walled, simple-septate hyphae 4–9 µm in diameter, and abundant long, obtuse, poorly differentiated cystidia with tramal origin and fine apical encrustation. Reid states that the hyphal structure is monomitic, but has also drawn long aseptate hyphae. Spores are ellipsoid, medium-sized. The description and illustrations provided by Melo and Hjortstam (2002) from Portugal are very similar to those of Reid, and agree largely with an Indian specimen we have studied.

Morphology suggests that A. griseofuscescens is not congeneric with Oxychaete cervinogilva, the latter being a polypore with regular pores, much looser hyphal structure without wide-spread encrustation, more regular and less-thick-walled hyphae, different type of cystidia with hymenial origin, differently shaped spores and lighter color of the basidiocarp.

Basidiocarp half-resupinate to pileate, annual, upper surface felt-like, yellowish brown with a lighter margin, lower surface brownish yellow or light ochraceous, 1–2 mm thick, caps projecting up to 3 cm, can fuse to form wide fruiting bodies. Consistency light cardboard-like when dry, somewhat flexible but easy to break apart. Pores regular, thin-walled, mouths rather smooth, (1)2–3 per mm. Cap context and subiculum yellowish brown, homogenous, upper surface not differentiated, up to 1 mm thick. Cap with a sharp, 1 mm wide sterile margin.

Hyphal system monomitic, clamps absent. Hyphae homogenous throughout, mostly thick-walled, always with a wide lumen, rather stiff and straight, CB− to CB(+), IKI−, KOH−, CRB lilac. Encrustation absent except on cystidia. Subicular hyphae interwoven, loosely arranged, (3.2)4–5.4(7.5) µm in diameter, walls up to 1.5 µm thick, mostly ≤1 µm. Contextual hyphae mostly horizontally arranged but not strictly parallel, (3.8)4–5.1(5.5) µm in diameter. Tramal tissue loose and easy to study, hyphae rather straight, parallel in lower trama, subparallel and interwoven towards subiculum, (3)3.5–4.8(6.2) µm in diameter, walls mostly 0.8–1.2 µm thick. Subhymenial hyphae thin- to slightly thick-walled, richly branching mostly like a corymb, not much winding.

Cystidia abundant, hymenial, thick-walled, often with an apical crystal cap, (15)20–40(55)×4.5–9, projecting 5–25 µm above hymenium.

Hymenium dominated by basidioles and cystidia, cells with constrictions especially in older basidiocarps. Basidia cylindrical to narrowly clavate, collapsing upon spore release and difficult to spot, with 4 sterigmata. Cystidioles absent.

Basidiospores cylindrical, curved, thin-walled, smooth, (5.9)6–8.4(8.9)×2.8–3.7(3.8) µm, L=6.93 µm, W=3.17 µm, Q’=(1.8)1.9–2.5(2.6), Q=2.19, CB−, IKI−, plasma stains in CB.

Figure 7. 

Microscopic characters of Oxychaete cervinogilvus, Schigel 5216, a subicular hyphae b tube trama and hymenium c hymenial cells d hymenial cystidia e spores.

Tropical Asia and Australia (Ryvarden and Johansen 1980). Not common in Indonesia although described from there.

Apparently prefers small-diameter dead wood of angiosperms. According to the description, the type was collected in a wet, shady forest in Javanese mountains. Australian collections we have seen are from drier localities (monsoon forest and city park).

Junghuhn (1838) provides a good painting of the species (Tab. IX), available through Google books (https://books.google.fi/books?id=AFJUAAAAcAAJ).

Phanerina mellea (Berk. & Broome) Miettinen.

Basidiocarps resupinate, yellow, fragile, pores shallow and large (1–4 per mm). Hyphal structure monomitic, simple-septate, loose, hyphae not swollen, wider (4–5 µm in diameter) in subiculum, a bit narrower in trama (3–4 µm). Hymenial branching corymb-like, subulate thin-walled cystidia present. Spores rather large (6–7×3 µm), cylindrical to narrowly ellipsoid.

This monotypic genus comes close to Riopa both morphologically and phylogenetically, though the two do not seem to form a monophyletic group (Figure 2). Morphological differences are summarized in Table 2.

Basidiocarp resupinate, yellow, ranging from yellowish cream to brownish yellow, 1–10×1–5 cm patches, 1(2) mm thick. Consistency fragile when dry. Pores shallow, somewhat irregular, splitting and eventually may turn dentate, 2–4 per mm, larger when split. Subiculum cream-colored, a bit lighter than pore surface, pellicular, cottony under the lens, 0.1–0.3 mm. Margin thinning out, smooth areas of several millimeters similar to tube bottoms may be present.

Hyphal system monomitic, clamps absent. Hyphae cylindrical, not much swollen, branching in sharp angles, rather similar throughout the basidiocarp, CB− to CB(+), IKI−, KOH−, CRB lilac. Large crystal clumps mostly of rhomboidal shape present in trama. Subiculum loose, hyphae interwoven, slightly thick-walled to thick-walled when old, (2)3–5(6.4) µm in diameter, walls mostly <0.5 µm thick, up to 1.2 µm in old basidiocarps. Tramal hyphae subparallel, thin- to slightly thick-walled, (2)3–3.8(4.8) µm in diameter. Subhymenium branching corymb-like, cells not sinuous, relatively easy to study.

Cystidia present but often rare, hymenial, thin-walled, subulate, rarely septate, naked, 40–80×5.8–9.2 µm, projecting 20–50 µm.

Hymenium relatively loose. Basidia clavate, 15–26×5.2–6.8 µm, with 4 wide, spindle-shaped sterigmata, 4–4.8×1.8 µm.

Basidiospores cylindrical to narrowly ellipsoid, usually abundant, with thin but distinct walls, smooth, (5.2)5.8–7.5(7.8)×(2.8)2.9–3.8(4.4) µm, L=6.55 µm, W=3.26 µm, Q’= (1.6)1.8–2.3(2.4), Q=2.01. Spore shape variation is rather large and abnormally broad ellipsoid spores can be present.

Figure 8. 

Microscopic characters of Phanerina mellea. a Subicular hyphae b tube trama c basidia, Miettinen 9134. Hymenial cystidia d Nuñez 503 e Ryvarden 10132. Spores f lectotype g Miettinen 9134 h Nuñez 503.

Described from Sri Lanka. We can confirm it from East Africa (Tanzania, Kenya), Japan (Okinawa), and Indonesia (New Guinea). Sequences of Chinese specimens are also available in the INSDC.

Grows on dead dicot trees, both standing and fallen, often in sun-exposed habitats.

East Asian, East African and New Guinean specimens have neither ITS sequence differences nor morphological differences, so we feel it is safe to assume that the type from Sri Lanka belongs to the same species. Morphologically the type specimen agrees very well with other material. Its spores are a little larger on average than in other specimens studied, but considering the large variability in size and shape of spores this is best interpreted as normal variance within species.

Phanerochaete alnea (Fr.) P. Karst.

We have chosen to apply the genus name Phanerochaete for most of the Phanerochaete clade, excluding the three polypore genera Oxychaete, Phanerina and Riopa (Figure 2). Morphologically, species in the Phanerochaete clade share microscopic characters such as simple-septate, relatively simple, loose hyphal structure, mid-sized hymenial cells, mid-sized straight cylindrical to narrow ellipsoid spores, and cystidia of subhymenial origin (Table 1 and 2). However, cystidia are rare and poorly differentiated or absent in three of the polypores (in the genera Phanerina and Riopa), and spores are distinctly curved in two species (Riopa). The third newly introduced polypore genus Oxychaete with its encrusted cystidia and large spores produces pileate and poroid basidiocarps. With the inclusion of these species, the genus Phanerochaete would become difficult to define morphologically.

Ceriporia inflata described by Jia and Cui (2012) belongs to Phanerochaetaceae with P. raduloides as the closest relative (Figure 2). The hymenophore of C. inflata is composed of irregular pores with lacerate mouths, and that of P. raduloides of irregular teeth. Also Ceriporia jianxiensis (no sequence available) described in the same paper as Ceriporia inflata may be closely related. Their identity against P. capitata and P. aculeata along with other species in the P. raduloides group should be checked.

For now we consider Ceriporia inflata a species of Phanerochaete. Splitting the hydnoid-poroid Phanerochaete of this group into a separate genus (possibly Phanerodontia Hjortstam) would make it necessary to split Phanerochaete into many small genera and would place morphologically very similar corticioid species into separate genera. For this reason we strongly prefer a wide concept of Phanerochaete that includes the hydnoid and poroid members, which are microscopically very similar to Phanerochaete sensu typi. See Tables 1 and 2 for characterization of the genus against similar genera in the Phanerochaetaceae.

Hjortstam and Ryvarden (2010) described Phanericium and Phanerodontia for a few species placed traditionally in Phanerochaete. Their Phanerodontia includes four taxa with smooth to hydnoid hymenophores. Phanerodontia is probably a taxonomic synonym of Phanerochaete. Although the type, P. dentata, has not been sequenced, two other members of the genus have (P. chrysosporium and P. magnoliae). They clearly belong to Phanerochaete, and according to the rpb1 dataset to the same subclade within the genus with smooth to poroid members (Figure 3). Phanerodontia dentata does not closely resemble any polypore genus discussed here (except Phanerochaete) with its combination of thin-walled tubular cystidia, long basidia, thick-walled subicular hyphae and ellipsoid spores.

Phanericium is a monotypic genus, and the type P. subquercinum is characterized by hydnoid, effused fruiting bodies, absence of cystidia, hyphae of even width throughout the fruiting body and broad ellipsoid spores. This set of characters does not closely match taxa discussed in detail in this paper, and more detailed study is needed to conclude whether the genus belongs to Phaerochaetaceae.

Phlebiopsis gigantea (Fr.) Jülich.

Phlebiopsis is typified by P. gigantea, a phlebioid species with agglutinated lower subiculum, well-developed basal layer/upper subiculum, thick-walled, simple-septate hyphae and thick-walled, conical, encrusted cystidia (lamprocystidia). Our wider concept of Phlebiopsis dilutes this set of characters, but lamprocystidia, interwoven subhymenium and tightly built subiculum remain as important characters for genus delimitation against similar genera of the Phanerochaetaceae (Table 1).

Hjortstamia crassa has been shown to be a close relative of Phlebiopsis, and has been included in that genus (Floudas and Hibbett 2015). We agree with this conclusion. The type species of Hjortstamia (H. friesii) has not been sequenced, but it is very similar to H. crassa. Thus Hjortstamia should for now be considered as a taxonomic synonym of Phlebiopsis. In addition to the above-mentioned Hjortstamia spp., a third similar species, H. papyrina, is combined to Phlebiopsis on morphological grounds.

The two main differences that have been emphasized to separate Hjortstamia from Phlebiopsis are reflexed basidiocarps and the loose subiculum of the former as opposed to the dense, agglutinated subiculum and totally effused basidiocarps of the latter. A closer look reveals that the difference is not as striking as often described. Whereas the genus type of Hjortstamia — H. friesii — and its close relative H. papyrina are distinctly pileate, basidiocarps of Hjortstamia crassa are much of the time fully resupinate or caps are small. Hjortstamia crassa also has an agglutinated upper subiculum or basal layer similar to agglutinated Phlebiopsis structures, as depicted by Wu and Chen (1992). Hjortstamia friesii has a tight (though not agglutinated) subicular layer composed of parallel hyphae as well (Hjortstam and Ryvarden 1989, Boidin and Gilles 2002). Subicular/cystidial hyphae of the above-mentioned species are strikingly similar, thick-walled, straight, stiff and sparsely septate.

A loose subiculum or pileate fruiting bodies do not seem to be useful characters separating Hjortstamia from Phlebiopsis, since loose and agglutinated species are widely intermixed phylogenetically within Phlebiopsis sensu lato (Figure 2). Hjortstamia crassa for instance is more closely related to the type species of Phlebiopsis than is Phlebiopsis flavidoalba with a very dense structure and effused fruiting bodies.

Sequences made available by Wu et al. (2010) include Phanerochaete brunneocystidiata and Phanerochaete laxa. The former is based on a paratype and the latter on the holotype. Wu combined the species in Hjortstamia due to sequence similarity to H. crassa. We haven’t seen authentic material, but according to original descriptions, they seem to share basic Phlebiopsis characters except that no agglutinated layer was described (Wu 2000, 2004).

Some Phlebiopsis species may turn out to belong to the Hapalopilus-Rhizochaete subclade instead of the Phlebiopsis subclade. For instance Phlebiopsis roumeguerei is nested within Phaeophlebiopsis as defined by Floudas and Hibbett (2015). More in-depth research is needed to settle genus classification for Rhizochaete and Phaeophlebiopsis-like taxa.

Riopa davidii D. A. Reid (=Riopa metamorphosa (Fuckel) Miettinen & Spirin).

White, resupinate polypores with shallow pores, 2–5 per mm. Hyphal structure monomitic, clamps absent. Hyphae thin- to slightly thick-walled, similar throughout the basidiocarp, hyphae not swollen, wider (3–5 µm in diameter) in subiculum, a bit narrower in trama (2.8–3.5 µm). Hymenial branching corymb-like. Thin-walled, poorly differentiated hymenial cystidia and conidia in one species. Spores curved cylindrical, sausage-like, thin-walled, mid-sized (4.5–6.5×2–3 µm).

Reid (1969) described Riopa as a monotypic genus with Riopa davidii D. A. Reid from Corsica as the sole species. Ryvarden (1991) considered R. davidii as a synonym of Ceriporia camaresiana (Bourdot & Galzin) Bondartsev & Singer, in effect making Riopa a synonym of Ceriporia. Pieri and Rivoire (1997) regarded Riopa davidii and Ceriporia camaresiana as separate species, and made the combination Ceriporia davidii. Their concept of the species was mixed, as can be seen already from the spore variation they report. Their specimens from mainland France did seem to represent a species of Ceriporia separate from C. camaresiana, and consequently Ceriporia davidii was adopted by Bernicchia (2005) and Ryvarden and Melo (2014).

We studied the type of Riopa davidii, and it turned out to be a more recent synonym for Ceriporia metamorphosa (Fuckel) Ryvarden & Gilb. After studying the French material of Ceriporia davidii collected by B. Rivoire, we could also conclude that Ceriporia davidii sensu Pieri and Rivoire (1997) needs to be described with a new name (Ceriporia pierii). Ceriporia pierii and also C. camaresiana belong to the Ceriporia clade and are only distantly related to Riopa (Figure 2).

Germany. Oestrich (Nassau): Mittelheimer Vorderwald, rotten trunk of Quercus, “Herbier Fuckel 1894, Herbier Barbey-Boissier”, no. 2008 (S F43290, designated here).

Czech Republic. Moravia: Lanžhot, Ranšpurk virgin forest, rotten trunk of Quercus robur, 5 Oct 1988 Pouzar (PRM871894, designated here, duplicate H 7008579).

Basidiocarp resupinate, white, cream or straw-colored, consistency fragile when dry. Forms patches of a few cm that can fuse to extensive basidiocarps, up to 2(-3) mm thick. Pores rounded angular, soon splitting and then irregular and sinuous, mouths smooth, 2–3(4) per mm, up to 2 mm wide when split. Subiculum very thin, arachnoid to pellicular, white to cream, often lighter than pores. Margin thinning out, usually no sterile margin.

Hyphal system monomitic, simple septate, hyphae rather homogenous throughout. Subicular hyphae interwoven, tissue loose, hyphae thin-walled to slightly thick-walled, (2.8)3.2–4.4(6.4) µm, walls rarely up to 1 µm in diameter. Tramal hyphae thin- to slightly thick-walled, interwoven but mostly vertically arranged, (2.2)2.9–3.5(4.0) µm in diameter. Subhymenium relatively loose, structure uncharacteristically simple for a polypore, composed of branching corymb-like, straight hyphae similar to those in trama. Crystals present as irregular aggregates of rhomboidal plates of various sizes, also fine encrustation present in subiculum. Shiny, hyaline, amorphous droplets floating around in CB.

Cystidia thin-walled, cylindrical, projecting above hymenial layer 5–20 µm, often covered with spores, (15)20–50×4–6.2 µm, born in subhymenium, poorly differentiated, appear as elongated basidioles, rare.

Hymenium loosely arranged, cells thin-walled. Basidia clavate, often projecting slightly above the rest of the hymenium, 15–28(35)×4–5.5(6.2) µm, with 4 sterigmata.

Basidiospores curved cylindrical, thin-walled, (4.2)5–6.6(8.2)×(2)2.2–3.1(3.5) µm, L=5.69 µm, W=2.59 µm, Q=2.19.

Anamorph known as Sporotrichum aurantiacum Link present or absent. Most but not all basidiocarps produce at least conidia in subiculum. When the anamorphic stage is well developed, it appears as an orange mass of conidia similar in shape to Haplotrichum aureum, in conjunction with basidiocarps or separately. Microscopically composed of thick-walled, ellipsoid to constricted conidia (8.2–12.2×5.2–7.8 µm, n=36/3) born singly as apical parts of slightly to clearly thick-walled, partly encrusted hyphae, (3.2)3.6–4.5(7.2) µm in diameter, walls ≤1.5 µm. The conidia and hyphae are yellow, the plasma of the conidia stains in CB, and the walls are CB− to CB(+) and slightly dextrinoid. In KOH the conidia stain pinkish red in masses. Wakefield (1952) proved in the lab that the polypore and conidial stages belong to the same organism.

Figure 9. 

Microscopic characters of Riopa. Riopa metamorphosa, epitype: a subicular hyphae b tube trama and hymenium c anamorph (Sporotrichum aurantiacum) d basidioles and basidia showing the characteristic corymb branching e hymenial cystidia. Spores of f Riopa metamorphosa drawn from the holotype of R. davidii g epitype of R. metamorphosa h holotype of R. pudens.

Temperate Europe: Germany, Poland, Slovakia, Czech Republic, Russia (Nizhny Novgorod), France (mainland, Corsica) (Vampola and Pouzar 1996, Pieri and Rivoire 1997). Northernmost records from Southern Norway (Ryvarden and Melo 2014) and Stockholm, Sweden (Romell 1926).

Grows preferably on rotten oak trunks. We have seen it on Eucalyptus and Salix caprea, also reported on Castanea, Juglands and Malus (Bourdot and Galzin 1928, Ryvarden and Gilbertson 1993, Pieri and Rivoire 1997).

Fuckel’s herbarium is in Wiesbaden (WIES), but its material is not available for loan. A duplicate of an original Fuckel specimen in Stockholm is chosen as the lectotype here. It represents an almost completely destroyed anamorphic stage. For practical reasons we also select an epitype from the Czech Republic.

Conidia have been reported from few other members of the Phanerochaetaceae: Phanerochaete chrysosporium (Burdsall and Eslyn 1974) and Hyphodermella rosae (Rahimlou et al. 2015). Riopa metamorphosa conidia are similar to the conidia of these species, particularly Hyphodermella rosae.

Indonesia. Riau: Indragiri Hulu, Bukit Aluran Babi, -0.838: 102.226, selectively logged forest slope, piece of a dicot log (15 cm in diameter, decay stage 2–4/5), 1 Jul 2004, Miettinen 8772 (ANDA, isotype H 7008582).

Pudens (adj., L), shy, modest, refers to the scarcity of distinct characters.

Basidiocarp resupinate, annual, cream, young parts white, up to half a meter wide, up to 4 mm thick. Consistency resistant to breaking but not tough. Pores thin-walled, mouths finely dentate, splitting when older, angular, 4–5 mm, 2–3 per mm when split/fused, 0.5–1.2 mm long. Subiculum white, 0.1–0.4 mm thick. Margin thinning out.

Hyphal system monomitic, clamps absent. Hyphae not swollen, rather similar in all parts. Subicular tissue loose, hyphae interwoven, thin- to thick-walled, mostly slightly thick-walled, (2.8)3.4–4.8(6.2) µm in diameter, walls rarely up to 1 µm thick. Tramal hyphae vertical, subparallel to interwoven, only moderately winding, thin-walled or slightly thick-walled, (2.4)2.8–3.2(4.2) µm in diameter. Shiny hyaline resin droplets floating around, fine-grained crystalline-amorphous substance glued on tramal hyphae in CB.

Cystidia not seen.

Hymenium relatively loosely arranged, basidia very thin-walled, collapsing soon, basidioles 10–14×3–4.2 µm.

Basidiospores curved cylindrical, thin-walled, (4.2)4.3–5.6(6.2)×(1.8)1.9–2.2(2.3) µm, L=5.01 µm, W=2.08 µm, Q=2.41.

Southeast Asia. Known from Riau, Sumatra and Fujian, China (the INSDC sequence JX623931, Cui 3238, ‘Ceriporia camaresiana’).

Grows on fairly rotten angiosperm wood. The type comes from low-land rainforest.

The species lacks any distinct characters. Cream-colored basidiocarp with non-inflated hyphae and corymb-subhymenium help to distinguish this species from Ceriporia spp. It is similar to Phanerochaete inflata and Ceriporia jianxiensis, but differs in having long-celled, narrower subicular hyphae (mostly <5 µm in diameter). The relatively small cylindrical curved spores exclude Oxyporus spp. and Emmia spp. Except for the smaller pores and the lack of cystidia and a conidial stage it is very similar to Riopa metamorphosa.

Sporotrichum aureum Link (= Riopa metamorphosa (Fuckel) Miettinen & Spirin)

Hughes (1958) lectotypified the genus with S. aureum. The original description of S. aureum does not permit accurate identification of the fungus in question, and no type seems to exist (Stalpers 1984). Fries (1932) considered S. aureum a synonym of Trichoderma aurantiacum Pers. 1796 (=Sporotrichum aurantiacum (Pers.) Fr). In his monograph of Sporotrichum Stalpers (1984) chose to follow Fries. He also considered S. aureum as an anamorphic stage of Riopa metamorphosa.

To formally settle the names Sporotrichum, S. aureus and S. aurantiacum we need to designate neotypes for the two species in question. In line with Stalper’s interpretation, we designate here the collection Vlasák 0511/15 (H 7008577) as the neotype of S. aureum Link, and collection Spirin 2456 (H 7029505) as the neotype of S. aurantiacum.

This makes Sporotrichum an older name available for Riopa under the ICBN Melbourne code article 59.1. However, adoption of Sporotrichum, traditionally a very heterogeneous set of anamorphs, for a small genus of polypores would only create confusion. Stalpers (1984) described the genus as a “litterbag” of conidiogenous fungi, and accepted only three species. According to him the teleomorphs of those three species are in separate genera (Laetiporus, Phanerochaete and Pycnoporellus/Riopa) that we now know are phylogenetically distinct. Although the type species Riopa produces an anamorph, we have seen no conidia in the other species of the genus (R. pudens). In this situation it is better to coin Riopa, a name without identity problems, for this polypore genus. We suggest conservation of the teleomorphic name Riopa D. A. Reid 1968 over the anamorphic Sporotrichum Link 1809.