Three new stipitate hydnoid fungi, Sarcodon coactus, S. grosselepidotus and S. lidongensis, are described and illustrated, based on morphological characteristics and nuc ITS rDNA + nuc LSU rDNA sequence analyses and a new record, S. leucopus, from China is reported. S. coactus is characterised by ellipsoid to round basidiocarps, reddish-brown to dark brown, felted pileal surface with white and incurved margins, simple-septate and partly short-celled generative hyphae and irregular subglobose, thin-walled, brown basidiospores with tuberculate ornamentation (tuberculi up to 1 μm long). S. grosselepidotus is characterised by infundibuliform to round, occasionally deeply fissured pileus, pale orange to dark ruby pileal surface with ascending and coarse scales, simple-septate generative hyphae and irregular ellipsoid to globose, thin-walled, brown basidiospores with tuberculate ornamentation (tuberculi up to 0.7 μm long). S. lidongensis is characterised by plano-convex to somewhat depressed and regular orbicular pileus, light brown to dark brown pileal surface with adhering squamose and purplish-brown, incurved and occasionally incised margin, cylindrical or broadened below stipe, simple-septate generative hyphae and irregular ellipsoid to subglobose, thin-walled basidiospores with tuberculate ornamentation (tuberculi up to 1 μm long). The absence of the clamp connection is the common morphological characteristic of these three new species; however, S. leucopus, a new record from China, has frequently clamped generative hyphae. Molecular analyses confirm the phylogenetic positions of three new and the new record species. The discriminating characters of these three new species and closely related species are discussed and a key to the species of Sarcodon from China is provided.

Bankeraceae, ITS and LSU, new species and record, taxonomy, Thelephorales

The genus Sarcodon Quél. ex P. Karst. (1881), together with Bankera Coker and Beers ex Pouzar (1955), Hydnellum P. Karst. (1896) and Phellodon P. Karst. (1881), belong to Bankeraceae, Thelephorales of Basidiomycota. They are a group of stipitate hydnoid fungi that inhabit the soil (Maas Geesteranus 1975).

Species of Bankeraceae are ectomycorrhizal fungi which associate with many kinds of angiosperm and gymnosperm trees, especially with Pinaceae and Fagaceae, such as Pinus strobus, Picea sitchensis, Fagus grandifolia, Quercus rubra and Castanea sativa (Maas Geesteranus 1975; Harrison 1984; Baird 1986; Baird et al. 2013) and usually occur in natural and comparatively undisturbed forests (Arnolds 1989). They can obtain energy from and transport nutrients to the host plants and are of great ecological significance in promoting forest vegetation recovery (Gardes and Bruns 1996; Erland and Taylor 1999). These fungi are vulnerable to impact due to changes in the environment, such as habitat loss, nitrogen deposition, decrease of host tree species and subsequently increased ground temperatures (Arnolds 1989; Otto 1992; Vesterholt et al. 2000; Newton et al. 2002; Arnolds 2010; Baird et al. 2013). In Europe, stipitate hydnoid fungi have been considered one of the most endangered groups of macrofungi and have been included in Red Data Lists (Hrouda 1999; Walleyn and Verbeken 2000; Hrouda 2005; Nitare 2006; Senn-Irlet et al. 2007), which have been used as indicators that forests need to be protected (Ainsworth 2005; Nitare 2019).

The genus Sarcodon is characterised by solitary to gregarious, stipitate, pileate basidiocarps, hydnaceous hymenophore, the monomitic hyphal system owning inflating or not inflating hyphae, the presence or absence of clamp connections and irregular ellipsoid to globose, tuberculate basidiospores which are brown in mass. Besides, the dry basidiocarps often produce farinaceous to fragrant or acidic odour (Maas Geesteranus 1971; Baird 1986; Arnolds 2003; Baird et al. 2013). In morphology, Sarcodon is closely related to Hydnellum, but the former usually has soft and fleshy basidiocarps and the latter has hard and corky basidiocarps (Maas Geesteranus 1971; Larsson et al. 2019). The macro-morphology of these two genera often depends on their environmental parameters, such as precipitation, temperature or obstructions. Additionally, the variable growth of basidiocarps makes it difficult to distinguish each other. Therefore, it is essential to support and confirm their identities using molecular sequence data (Baird et al. 2013). Recent molecular phylogenetic analyses reveal that Sarcodon and Hydnellum form paraphyletic lineage and suggest using the spore length as the delimitation between the two genera. Hydnellum species had spore lengths in the range 4.45−6.95 µm, while the corresponding range for Sarcodon was 7.4−9 µm (Larsson et al. 2019).

Most species of Sarcodon have been reported from the northern temperate hemisphere (Maas Geesteranus 1971, 1975; Baird 1986; Stalpers 1993; Pegler et al. 1997; Dai 2011) and are commonly found in North America (Harrison 1964, 1984; Baird 1985, 1986; Baird et al. 2013), Netherlands (Maas Geesteranus 1956, 1976), Spain (Pérez-De-Gregorio et al. 2011), France (Pieri and Rivoire 1994), Russia (Baird 1985) and Italy (Caclalli and Caroti 2005). Some species have also been recorded from southern hemisphere, such as New Zealand (Maas Geesteranus 1964, 1971, 1975) and Australia (Mleczko et al. 2011; Magnago et al. 2015; Hahn et al. 2018). Around 59 species have been described or transferred to the genus according to Index Fungorum (http://www.indexfungorum.org/) and MycoBank, but only five taxa have been reported from China (Dai 2011). In addition, some species of Sarcodon have medicinal functions, for instance, lowering cholesterol, antioxidant, antibacterial, anti-tumour, improving immunity etc. (Wu et al. 2019).

Investigations of hydnaceous fungi in China have been carried out in recent decades and many Sarcodon specimens have been collected. During the study of these specimens, three undescribed species and a new record species have been identified using morphological characters and phylogenetic analyses of nuc rDNA ITS1-5.8S-ITS2 combined with nuc 28S rDNA sequences. Here, we describe them in this paper.

Three new species of Sarcodon were described, based on the morphological characteristics and molecular data and were the first new species described from China. Phylogenetic analyses of the nuc ITS rDNA + nuc LSU rDNA dataset by ML, MP and Bayes in this study showed a low level of support in the deeper nodes of the topology, but high support at the species level. The result is in keeping with previous reports (Baird et al. 2013; Larsson et al. 2019).

The felted pileal surface is the main feature of Sarcodon coactus and this is consistent with S. repandus and S. thwaitesii. However, S. repandus differs from S. coactus by a larger pileus (up to 50 mm vs. 35 mm in S. coactus) with longer spines (up to 4 mm vs. 2.1 mm in S. coactus), clamped hyphae and wider hyphae in the context (up to 25 µm) (Maas Geesteranus 1971). S. thwaitesii resembles S. coactus in having an azonate pileal surface, central and hollow stipe when old and thin-walled hyphae in trama. However, S. thwaitesii differs from S. coactus by slightly longer (up to 3 mm vs. 2.1 mm in S. coactus) and not decurrent spines, blue-green tissues in KOH, clamped hyphae in all parts of the basidiocarp, wider basidia (10–11 µm vs. 6.2–9 μm in S. coactus) with longer sterigmata (5.4–9 µm vs. 3.1–5.2 μm in S. coactus) and larger basidiospores (8.1–9.4 × 5.8–7.2 µm vs. 5.7–7 × 4.7–5.9 μm in S. coactus) (Maas Geesteranus 1971).

Sarcodon grosselepidotus presents a distinct characteristic: pileal surface with ascending and coarse scales, that coincide with that of S. imbricatus and S. lepidus (Maas Geesteranus 1975; Baird et al. 2013). However, S. imbricatus is differentiated from the new species by having longer spines (up to 8 mm vs. 1.4 mm in S. grosselepidotus), clamped hyphae in all parts of the basidiocarp, presence of gloeoplerous-like hyphae and larger basidiospores (8–9 × 7–8 μm vs. 5.1–6.4 × 4.1–5.9 μm in S. grosselepidotus) (Maas Geesteranus 1971; Baird et al. 2013). S. lepidus differs from S. grosselepidotus by having longer spines (up to 3 mm vs. 1.4 mm in S. grosselepidotus), farinaceous odour, wider hyphae in the context and narrower basidiospores (3.6–4.3 µm vs. 4.1–5.9 μm in S. grosselepidotus) (Maas Geesteranus 1975).

Sarcodon coactus and S. grosselepidotus are closely related in the phylogenetic tree and share similar morphological and anatomical characteristics: solitary to gregarious basidiocarps with round pileus, central and columniform stipe, decurrent spines, context tissue becoming olivaceous in KOH and isolated or grouped tuberculi. However, S. grosselepidotus can be differentiated by infundibuliform basidiocarps, fissured pileus, coarse and scaly pileal surface, shorter spines (up to 1.4 mm vs. 2.1 mm in S. coactus) and slightly shorter tuberculi (up to 0.7 μm vs. 1 μm in S. coactus).

Sarcodon lidongensis and S. scabrosus reveal a close phylogenetic relationship according to the phylogenetic tree. In morphology, S. lidongensis is similar to S. scabrosus in having a single or gregarious basidiocarp with convex to planar or depressed pileus, brown and scaled pileal surface, central and terete stipe, olivaceous tissues in KOH and basidiospores of similar shape. However, S. scabrosus is differentiated by a larger pileus (up to 15 cm across) with longer spines (up to 8 mm vs. 1 mm in S. lidongensis), wider basidia (7–9 μm vs. 3.0–7.2 μm in S. lidongensis) with longer sterigmata (4–5 μm vs. 2–3 μm in S. lidongensis) and larger basidiospores (6–7 × 5–7 μm vs. 4.1–6 × 4–5 μm in S. lidongensis) (Maas Geesteranus 1971; Baird 1986; Baird et al. 2013).

Sarcodon joeides is similar to S. lidongensis in having simple basidiocarps with plano-convex or depressed pileus, mottling or tear-like pileal surface, appressed scales, central and terete stipe, olivaceous tissue in KOH, inflated and interwoven hyphae in the context and tuberculate basidiospores of similar shape. However, it differs from S. lidongensis in having longer, decurrent to strongly decurrent spines (up to 3 mm vs. 1 mm in S. lidongensis), presence of gloeoplerous-like hyphae, longer basidia sterigmata (4–5 μm vs. 2–3 μm in S. lidongensis) and wider basidiospores (5–6 μm vs. 4–5 μm in S. lidongensis) (Baird et al. 2013).

The specimens, involved in this study, were collected from the forests dominated by Fagaceae trees such as Quercus acutissima, Lithocarpus dealbatus, Castaopsis orthacantha and a small portion of coniferous trees, for instance, Pinus armandii. We speculated that these species may form an ectomycorrhizal association with Fagaceae trees. The new record sample was fully identical with S. leucopus described by Mleczko et al. (2011) in morphology and molecular analysis and pine and spruce were primary ectomycorrhizal companions of this fungus.

This research was financed by the National Natural Science Foundation of China (Project Nos. 31770028 & 31970017) and the Biodiversity Investigation, Observation and Assessment Program (2019–2023) of the Ministry of Ecology and Environment of China.