Taxonomy and Phylogeny of the Fomitopsis pinicola Complex With Descriptions of Six New Species From East Asia

Abstract

Fomitopsis pinicola is a common brown-rot fungal species found in northern hemisphere. It grows on many different gymnosperm and angiosperm trees. Recent studies show that it is a species complex; three species from North America and one species from Europe have been recognized in this complex. In the current study, six new species in the Fomitopsis pinicola complex were discovered from East Asia, based on morphological characters and phylogenetic analyses inferred from the sequence data of the internal transcribed spacer (ITS) regions, the second subunit of RNA polymerase II (RPB2), and the translation elongation factor 1-α gene (TEF). Detailed descriptions of the six new species are provided. Our results also indicates that species of the F. pinicola complex from East Asia usually have limited distribution areas and host specialization.

Introduction

Fomitopsis P. Karst. was established by Karsten and typified by F. pinicola (Sw.) P. Karst. (Karsten, 1881). It is characterized by a perennial or annual growth habit, is sessile to effused-reflexed, has tough to woody hard basidiocarps, has a white to tan or pinkish-colored pore surface with mostly small and regular pores, has a dimitic to trimitic hyphal system with clamped generative hyphae, and has a hyaline, thin-walled, smooth, and ellipsoid to subglobose basidiospores which are negative in Melzer’s reagent; it causes a brown rot (Ryvarden and Johansen, 1980; Gilbertson and Ryvarden, 1986; Ryvarden and Gilbertson, 1993; Núñez and Ryvarden, 2001; Han et al., 2016).

Fomitopsis pinicola has been intensively studied because it has the function of dispelling wind-evil and dampness, and has anti-tumor (Dai et al., 2009; Sun et al., 2016), antifungal, antioxidant, immunomodulation, and neuroprotective activities (Guler et al., 2009; Bao et al., 2015; Sun et al., 2016; Guo and Wolf, 2018). Högberg et al. (1999) showed that all European populations of F. pinicola belong to one intersterility group. Ryvarden and Stokland (2008) described Fomitopsis ochracea Ryvarden & Stokland from Alberta on Populus tremuloides that was distinguished from F. pinicola by substrate preference, basidiospore morphology, and match flame test to the lacquered pilei surface. Subsequently, this species was proven to belong to the F. pinicola complex (Haight et al., 2019). Haight et al. (2016) suggested that F. pinicola is a species complex comprised of at least four well-supported phylogenetic species, three in North America (F. ochracea and two previously undescribed species) and one in Europe (F. pinicola). Haight et al. (2019) described two new species: F. mounceae Haight & Nakasone and F. schrenkii Haight & Nakasone from North America in the F. pinicola complex. Until now, four species have been recognized in the F. pinicola complex; F. mounceae, F. ochracea, and F. schrenkii from North America and F. pinicola from Europe.

In some cases, fungi species boundaries based on morphology misrepresents the number of existing species (Leavitt et al., 2011). Due to geographic isolation, lack of migration, and genetic drift there may be variation among populations, although this genetic variation is not always obvious (Haight et al., 2016). Cryptic species of species complexes are proving to be extremely common in higher fungi, particularly those with wide geographic distributions or host ranges (Haight et al., 2016); they share similar morphological characteristics and phylogenetic relationships to known species. More cryptic species could be discovered by combining evidence of morphological characters, molecular data, host trees, and distribution areas in species complexes (Liu et al., 2021).

In recent years, taxonomic and phylogenetic studies of Fomitopsis have been carried out in China and several new species have been described (Li et al., 2013; Han et al., 2014, 2016; Han and Cui, 2015; Liu et al., 2019), but none have been focused on the F. pinicola complex. Samples collected from China were still identified as F. pinicola complex in these studies. With more and more specimens collected from different areas of China, Vietnam, and of East Asia, six new species of the F. pinicola complex have been discovered based on morphological characters and phylogenetic analysis of ITS + RPB2 + TEF gene regions.

Materials and Methods

Taxa Sampling and Morphological Study

The examined specimens were deposited in the herbarium of the Institute of Microbiology, Beijing Forestry University (BJFC, Beijing, P. R. China). Morphological descriptions and abbreviations used in this study follow Han et al. (2016) and Liu et al. (2019).

DNA Extraction and Molecular Analyses

The procedures for DNA extraction and polymerase chain reaction (PCR) used in this study were the same as described by Chen et al. (2017) and Song and Cui (2017). The primer pairs ITS5 and ITS4 for ITS regions, fRPB2-f5F and bRPB2-7.1R for the RPB2 gene, and EF1-983 F and EF1-1567R for the TEF gene used in this study are the same as in previous studies (White et al., 1990; Rehner, 2001; Matheny, 2005).

The PCR cycling schedules for different DNA sequences of ITS, RPB2, and TEF genes used in this study followed those used in Zhu et al. (2019) and Sun et al. (2020) with some modifications. The PCR procedure for ITS was the initial denaturation at 95°C for 3 min, followed by 35 cycles of denaturation at 94°C for 40 s, annealing at 54°C for 45 s, and extension at 72°C for 1 min, and a final extension at 72°C for 10 min. The PCR procedure for RPB2 was the initial denaturation at 94°C for 2 min, followed by 37 cycles of denaturation at 94°C for 45 s, annealing at 56°C for 90 s, and extension at 72°C for 2 min, and a final extension at 72°C for 10 min. The PCR procedure for TEF was the initial denaturation at 95°C for 3 min, followed by 35 cycles of denaturation at 94°C for 40 s, annealing at 54–57°C for 45 s and extension at 72°C for 1 min, and a final extension at 72°C for 10 min. The PCR products were purified and sequenced at the Beijing Genomics Institute (BGI), China, with the same primers. All newly generated sequences were deposited in GenBank (Table 1). Additional sequences for phylogenetic analyses were downloaded from GenBank (Table 1). All sequences were aligned in MAFFT 7 (Katoh and Standley, 2013)¹ and manually adjusted in BioEdit (Hall, 1999). Alignments were spliced in Mesquite (Maddison and Maddison, 2017). The missing sequences were coded as “N,” ambiguous nucleotides were coded as “N” followed Chen et al. (2017). The final concatenated sequence alignment was deposited in TreeBase² (submission ID: 27439).

TABLE 1.

A list of species, specimens, and GenBank accession numbers of sequences used in this study.

Species name	Sample no.	Locality	GenBank accessions
			ITS	RPB2	TEF
Antrodia tanakae	Cui 9743	China	KR605814	KR610833	KR610743
A. tanakae	Yuan 1106	China	KP715313	KR610835	KP715343
Daedalea quercina	Dai 12152	Czechia	KP171207	KR610809	KR610717
D. quercina	Dai 2260	Sweden	KR605792	KR610808	KR610718
Fomitopsis abieticola	Cui 10532	China	MN148230	MN158174	MN161745
F. abieticola	Cui 10521	China	MN148231	—	MN161746
F. betulina	Cui 10756	China	KR605797	KR610815	KR610725
F. betulina	Dai 11449	China	KR605798	KR610816	KR610726
F. cana	Cui 6239	China	JX435777	KR610761	KR610661
F. cana	Dai 9611	China	JX435776	KR610762	KR610660
F. durescens	Overholts 4215	United States	KF937293	—	—
F. durescens	O 10796	Venezuela	KF937292	KR610766	KR610669
F. hengduanensis	Cui 16259	China	MN148232	MN158175	MN161747
F. hengduanensis	Cui 17056	China	MN148233	MN158176	MN161748
F. kesiyae	Cui 16437	Vietnam	MN148234	MN158177	MN161749
F. kesiyae	Cui 16466	Vietnam	MN148235	MN158178	MN161750
F. massoniana	Cui 2848	China	MN148236	—	MN161751
F. massoniana	Cui 9058	China	MN148237	—	MN161752
F. massoniana	Cui 11288	China	MN148238	MN158179	MN161753
F. massoniana	Cui 11304	China	MN148239	—	MN161754
F. meliae	Dai 10035	China	KR605774	—	KR610683
F. meliae	Ryvarden 16893	Unknown	KR605776	KR610775	KR610681
F. mounceae	AFTOL ID 770	United States	AY786056	AY864874	AY705967
F. mounceae	DR 366	United States	KF169624	KF169693	KF178349
F. mounceae	JAG 08 19	United States	KF169626	KF169695	KF178351
F. mounceae	JEH 78	Canada	KF169629	KF169698	KF178354
F. mounceae	Tuomo Niemelä 2530	Canada	MN148240	—	MN161755
F. mounceae	Teuvo Ahti 60351	Canada	MN148241	—	MN161756
F. mounceae	OM 18782	United States	MN148242	—	MN161757
F. mounceae	Spirin 8367	United States	MN148243	—	MN161758
F. ochracea	HHB 19692	United States	KF169594	KF169663	KF178319
F. ochracea	HHB 19670	United States	KF169593	KF169662	KF178318
F. ochracea	JEH 38	United States	KF169603	KF169672	KF178328
F. ochracea	LT 18	United States	KF169616	KF169685	KF178341
F. ochracea	OM 18568	United States	MN148244	—	MN161759
F. ochracea	OM 18673	United States	MN148245	—	MN161760
F. ochracea	Spirin 8165	United States	MN148246	—	MN161761
F. pinicola	FCUG 2056	Sweden	KF169654	KF169723	KF178379
F. pinicola	HK 19330	Russia	KF169655	KF169724	KF178380
F. pinicola	LT 323	Estonia	KF169651	KF169720	KF178376
F. pinicola	LT 319	Estonia	KF169652	KF169721	KF178377
F. pinicola	AT Fp 1	Sweden	MK208852	MK236362	MK236359
F. pinicola	AT Fp 2	Sweden	MK208853	MK236363	MK236360
F. schrenkii	FP 105881 R	United States	KF169641	KF169710	KF178366
F. schrenkii	JEH 144	United States	KF169621	MK208857	MK236355
F. schrenkii	JEH 150	United States	KF169622	MK208858	MK236356
F. schrenkii	JV 1209/61 J	United States	MN148247	MN158180	MN161762
F. schrenkii	Inkeri Ahonen 58	United States	MN148248	—	MN161763
F. subpinicola	Cui 9836	China	MN148249	MN158181	MN161764
F. subpinicola	Cui 9819	China	MN148250	—	MN161765
F. subpinicola	Dai 11101	China	MN148251	MN158182	MN161766
F. subpinicola	Dai 11206	China	MN148252	MN158183	MN161767
F. subpinicola	Dai 13480	China	MN148253	MN158184	MN161768
F. subpinicola	Yuan 4912	China	MN148254	—	MN161769
F. subtropica	Cui 10578	China	KR605787	KR610791	KR610698
F. subtropica	Cui 10140	China	JQ067651	KR610789	KR610699
F. tianshanensis	Wei 1568	China	MN148255	—	MN161770
F. tianshanensis	Wei 1473a	China	MN148256	—	MN161771
F. tianshanensis	Wei 1462a	China	MN148257	—	MN161772
F. tianshanensis	Cui 16821	China	MN148258	—	MN161773
F. tianshanensis	Cui 16823	China	MN148259	—	MN161774
F. tianshanensis	Cui 16825	China	MN148260	—	MN161775
F. tianshanensis	Cui 16828	China	MN148261	—	MN161776
F. tianshanensis	Cui 16830	China	MN148262	—	MN161777
Laetiporus zonatus	Dai 13633	China	KX354481	KX354676	KX354635
L. zonatus	Cui 10404	China	KF951283	KT894797	KX354639
Niveoporofomes spraguei	JV 0509/62	United States	KR605786	KR610788	KR610697
N. spraguei	4638	France	KR605784	KR610786	KR610696
Rhodofomes roseus	Cui 10520	China	KC507162	KR610783	KR610692
R. roseus	Cui 10633	China	KR605782	KR610784	KR610693
Rhodofomitopsis feei	LR 14115	Costa Rica	KF999923	—	—
R. feei	JV 0610/K9-Kout	Mexico	KF999922	—	KR610673
Rubellofomes cystidiatus	Cui 5481	China	KF937288	KR610765	KR610667
R. cystidiatus	Yuan 6304	China	KR605769	—	KR610668

New sequences are shown in bold.

Phylogenetic analyses approaches used in this study followed Han et al. (2016) and Cui et al. (2019). The congruences of the 3-gene (ITS, RPB2 and TEF) were evaluated with the incongruence length difference (ILD) test (Farris et al., 1994) implemented in PAUP^∗ 4.0b10 (Swofford, 2002), under heuristic search and 1000 homogeneity replicates. The sequences of Daedalea quercina (L.) Pers obtained from GenBank were used as outgroups for the phylogeny of the Fomitopsis pinicola complex, and sequences of Laetiporus zonatus B.K. Cui & J. Song were used as outgroups for the phylogeny of the Fomitopsis pinicola complex and related taxa. A maximum parsimony (MP) analysis was performed in PAUP^∗ version 4.0b10 (Swofford, 2002). A maximum likelihood (ML) analysis was performed in RAxmL v.7.2.8 with a GTR + G + I model (Stamatakis, 2006). Bayesian inference (BI) was calculated by MrBayes 3.1.2 (Ronquist and Huelsenbeck, 2003) with a general time reversible (GTR) model of DNA substitution and a gamma distribution rate variation across sites determined by MrModeltest 2.3 (Posada and Crandall, 1998; Nylander, 2004). Clade robustness was assessed using a bootstrap (BT) analysis with 1000 replicates (Felsenstein, 1985). The branch support was evaluated with a bootstrapping method of 1000 replicates (Hillis and Bull, 1993). Branches that received bootstrap supports for the MP and ML, greater than or equal to 75% and Bayesian posterior probabilities (BPP) greater than or equal to 0.95, were considered as significantly supported (Shen et al., 2019; Sun et al., 2020). The phylogenetic tree was visualized using FigTree v1.4.2³.

Results

Molecular Phylogeny

The combined 3-gene (ITS, RPB2, TEF) dataset to infer the phylogeny of species in the Fomitopsis pinicola complex included sequences from 52 fungal samples representing 11 taxa. The dataset had an aligned length of 1750 characters including gaps (553 characters for ITS, 641 characters for RPB2, 556 characters for TEF), of which 1403 characters were constant, 32 were variable and parsimony-uninformative, and 315 were parsimony-informative. Maximum parsimony analysis yielded 12 equally parsimonious trees (TL = 470, CI = 0.785, RI = 0.872, RC = 0.684, HI = 0.215). The best model for the combined ITS + RPB2 + TEF sequences dataset estimated and applied in the Bayesian analysis was GTR + I + G with equal frequency of nucleotides. Bayesian analysis and ML analysis resulted in a similar topology as the MP analysis, and only the MP tree inferred from the combined three-gene dataset is shown in Figure 1.

FIGURE 1.

Maximum parsimony tree illustrating the phylogeny of the Fomitopsis pinicola complex based on the combined sequences dataset of ITS + RPB2 + TEF. Daedalea quercina served as the outgroup. Branches are labeled with maximum likelihood bootstrap higher than 50%, maximum parsimony bootstrap proportions higher than 50% and Bayesian posterior probabilities more than 0.95. Bold names = New species.

The combined three-gene (ITS, RPB2, TEF) dataset infer the phylogeny of species in the Fomitopsis pinicola complex and the related group included sequences from 74 fungal samples representing 21 taxa. The dataset had an aligned length of 1848 characters including gaps (641 characters for ITS, 641 characters for RPB2, 566 characters for TEF), of which 1063 characters were constant, 41 were variable and parsimony-uninformative, and 744 were parsimony-informative. MP analysis yielded 10 equally parsimonious trees (TL = 2428, CI = 0.521, RI = 0.762, RC = 0.397, HI = 0.479). The best model for the concatenate sequence dataset estimated and applied in the Bayesian inference was GTR + I + G with an equal frequency of nucleotides. Bayesian analysis and ML analysis resulted in a similar topology as the MP analysis, and only the MP tree inferred from the combined three-gene sequences dataset is shown in Figure 2.

FIGURE 2.

Maximum parsimony tree illustrating the phylogeny of the Fomitopsis pinicola complex and related group based on the combined sequences dataset of ITS + RPB2 + TEF. Laetiporus zonatus served as the outgroup. Branches are labeled with maximum likelihood bootstrap higher than 50%, maximum parsimony bootstrap proportions higher than 50% and Bayesian posterior probabilities more than 0.95. Bold names = New species.

The phylogenetic trees (Figures 1, 2) generated by Maximum parsimony, Maximum likelihood and Bayesian analyses showed that the six new species, Fomitopsis abieticola, F. hengduanensis, F. kesiyae, F. massoniana, F. subpinicola, and F. tianshanensis grouped together with F. mounceae, F. ochracea, F. pinicola, and F. schrenkii, thus, the species number of the F. pinicola complex increased to 10 around the world.

Taxonomy

Fomitopsis abieticola B.K. Cui, M.L. Han & Shun Liu, sp. nov. (Figures 3A,B, 4).

FIGURE 3.

Basidiocarps of the Fomitopsis pinicola complex species. (A,B) F. abieticola; (C,D) F. hengduanensis; (E,F) F. kesiyae; (G,H) F. massoniana; (I,J) F. subpinicola; (K,L) F. tianshanensis. Bars: A,B,D,E,F = 2 cm; G,H = 1 cm; C,I,J = 3 cm; K,L = 5 cm.

FIGURE 4.

Microscopic structures of Fomitopsis abieticola (drawn from the holotype). (A) Basidiospores; (B) Basidia and basidioles; (C) Cystidioles; (D) Hyphae from trama; (E) Hyphae from context. Bars: A–E = 10 μm.

MycoBank: MB 838908

Fomitopsis abieticola is characterized by its large pores (2–4 per mm), long cystidioles (17.5–50.2 × 4.3–9.5 μm), long basidia (20.8–40.5 × 5.5–11.5 μm) and big basidiospores (7–9 × 4–5 μm), and grows on Abies.

Type. — CHINA. Yunnan Province, Shangri-La County, Pudacuo National Park, on stump of Abies, 24 September 2011, Cui 10532 (Holotype, BJFC 011427).

Etymology. —Abieticola (Lat.), refers to the host tree genus Abies.

Basidiocarps. —Annual to perennial, pileate, sessile, solitary, hard corky, without odor or taste when fresh, woody hard and light in weight upon drying. Pilei semicircular to ungulate, projecting up to 6.5 cm long, 8.5 cm wide, 2.5 cm thick at base. Pileal surface cream to pinkish buff when fresh, becoming honey-yellow to grayish brown when dry, glabrous, small nodules appear near the base, rough, azonate; margin cream, slightly paler than pileal surface, obtuse. Pore surface cream to pinkish buff when fresh, becoming buff to curry-yellow when dry; sterile margin distinct, white to cream when fresh, becoming olivaceous buff to clay-buff when dry, up to 10 mm wide; pores round to angular, 2–4 per mm; dissepiments slightly thick to thick, entire. Context cream to straw-yellow, woody hard, up to 1.5 cm thick. Tubes concolorous with pore surface, woody hard, up to 1 cm long.

Hyphal structure. —Hyphal system dimitic; generative hyphae bearing clamp connections; skeletal hyphae IKI–, CB–; tissues unchanged in KOH.

Context. —Generative hyphae infrequent, hyaline, thin-walled, rarely branched, 2.5–5 μm in diam; skeletal hyphae dominant, yellowish brown to cinnamon brown, thick-walled with a narrow lumen to subsolid, rarely branched, straight, interwoven, 2.3–8.2 μm in diam.

Tubes. —Generative hyphae infrequent, hyaline, thin-walled, rarely branched, 1.9–3.2 μm in diam; skeletal hyphae dominant, hyaline, thick-walled with a wide lumen, occasionally branched, more or less straight, interwoven, 2.2–7.2 μm in diam. Cystidia absent, but fusoid cystidioles occasionally present, hyaline, thin-walled, 17.5–50.2 × 4.3–9.5 μm. Basidia clavate, bearing four sterigmata and a basal clamp connection, 20.8–40.5 × 5.5–11.5 μm; basidioles dominant, in shape similar to basidia, but smaller.

Spores. —Basidiospores oblong-ellipsoid to ellipsoid, hyaline, thin-walled, smooth, IKI–, CB–, 7–9(–9.2) × (3.2–)4–5 μm, L = 7.85 μm, W = 4.26 μm, Q = 1.83–1.89 (n = 60/2).

Type of rot. —Brown rot.

Additional specimen (paratype) examined: CHINA. Yunnan Province, Shangri-La County, Pudacuo National Park, on stump of Abies, 24 September 2011, Cui 10521 (BJFC 011416).

Fomitopsis hengduanensis B.K. Cui & Shun Liu, sp. nov. (Figures 3C,D, 5).

FIGURE 5.

Microscopic structures of Fomitopsis hengduanensis (drawn from the holotype). (A) Basidiospores; (B) Basidia and basidioles; (C) Cystidioles; (D) Hyphae from trama; (E) Hyphae from context. Bars: A–E = 10 μm.

MycoBank: MB 838909

Fomitopsis hengduanensis is characterized by laccate pileus with pale dark gray to reddish brown surface at base and cream to flesh-pink toward the margin when fresh, oblong-ellipsoid to ellipsoid basidiospores (5.2–6 × 3.2–3.6 μm) and is distributed in high altitude areas of the Hengduan Mountains.

Type. —CHINA, Yunnan Province, Lanping County, Tongdian, Laojunshan of Hengduan Mountains, Luoguqing, on dead tree of Picea, 18 September 2017, Cui 16259 (Holotype, BJFC 029558).

Etymology. —Hengduanensis (Lat.), refers to the species distributed in the area of Hengduan Mountains.

Basidiocarps. —Annual to perennial, pileate, sessile, solitary, hard corky, without odor or taste when fresh, woody hard and light in weight upon drying. Pilei applanate, semicircular to ungulate, projecting up to 7.5 cm long, 9 cm wide, 3 cm thick at base. Pileal surface laccate, colors varied but usually pale dark gray to reddish brown at base and cream to flesh-pink toward the margin when fresh, curry-yellow, mouse-gray to reddish brown at base and buff to clay-buff toward the margin when dry, glabrous, sulcate, concentrically zonate; margin acute to obtuse. Pore surface white to cream when fresh, becoming buff to straw-yellow when dry; sterile margin distinct, cream, up to 4 mm wide; pores round to angular, 6–8 per mm; dissepiments thick, entire. Context cream to straw-yellow, woody hard, up to 1.4 cm thick. Tubes concolorous with pore surface, woody hard, up to 0.5 cm long.

Hyphal structure. —Hyphal system dimitic; generative hyphae bearing clamp connections; skeletal hyphae IKI–, CB–; tissues unchanged in KOH.

Context. —Generative hyphae infrequent, hyaline, thin- to slightly thick-walled, rarely branched, 1.9–4.3 μm in diam; skeletal hyphae dominant, hyaline to pale yellowish, thick-walled with a narrow lumen to subsolid, rarely branched, straight, interwoven, 2–8.5 μm in diam.

Tubes. —Generative hyphae infrequent, hyaline, thin-walled, rarely branched, 1.3–3.5 μm in diam; skeletal hyphae dominant, hyaline, thick-walled with a wide lumen, occasionally branched, more or less straight, interwoven, 1.7–7.5 μm in diam. Cystidia absent, but fusoid cystidioles occasionally present, hyaline, thin-walled, 13.2–36.5 × 2.5–5.4 μm. Basidia clavate, bearing four sterigmata and a basal clamp connection, 16.6–34.5 × 5.4–10.2 μm; basidioles dominant, in shape similar to basidia, but smaller.

Spores. —Basidiospores oblong-ellipsoid to ellipsoid, hyaline, thin-walled, smooth, IKI–, CB–, (5–)5.2–6(–6.2) × (3–)3.2–3.6(–4) μm, L = 5.44 μm, W = 3.41 μm, Q = 1.57–1.63 (n = 60/2).

Type of rot. —Brown rot.

Additional specimen (paratype) examined: CHINA. Yunnan Province, Lijiang, Yulong xueshan of Hengduan Mountains, on fallen trunk of Picea, 16 September 2018, Cui 17056 (BJFC 030355).

Fomitopsis kesiyae B.K. Cui & Shun Liu, sp. nov. (Figures 3E,F, 6).

FIGURE 6.

Microscopic structures of Fomitopsis kesiyae (drawn from the holotype). (A) Basidiospores; (B) Basidia and basidioles; (C) Cystidioles; (D) Hyphae from trama; (E) Hyphae from context. Bars: A–E = 10 μm.

MycoBank: MB 838910

Fomitopsis kesiyae is characterized by its buff yellow to orange-yellow buff pileal surface when fresh, reddish brown to yellowish brown when dry, and grows on Pinus kesiya and is distributed in tropical areas of Vietnam.

Type. — VIETNAM. Dam Dong Province, Da Lat, Bidoup Nui Ba National Park, on living tree of Pinus kesiya, 15 October 2017, Cui 16437 (Holotype, BJFC 029736).

Etymology. — Kesiyae (Lat.), refers to the host tree species Pinus kesiya.

Basidiocarps. — Annual, pileate, sessile, hard corky, without odor or taste when fresh, woody hard and light in weight upon drying. Pilei applanate, semicircular to sectorial, projecting up to 4.7 cm long, 6.5 cm wide, 4 cm thick at base. Pileal surface laccate, buff yellow to orange-yellow buff when fresh, becoming reddish brown to yellowish brown when dry, glabrous, sulcate, azonate; margin cream, distinctly paler than the pileal surface, obtuse. Pore surface white to cream when fresh, olivaceous buff to cinnamon-buff when dry; sterile margin distinct, buff to honey-yellow, up to 3 mm wide; pores round to angular, 6–8 per mm, dissepiments thick, entire. Context cream to straw-yellow, corky, up to 1.2 cm thick. Tubes concolorous with pore surface, hard corky, up to 1 cm long.

Hyphal structure. — Hyphal system dimitic; generative hyphae bearing clamp connections; skeletal hyphae IKI–, CB–; tissues unchanged in KOH. Small polyhedric or irregular crystals present among context and tubes.

Context. — Generative hyphae infrequent, hyaline, thin- to slightly thick-walled, rarely branched, 1.9–4.2 μm in diam; skeletal hyphae dominant, yellowish brown to cinnamon brown, thick-walled with a wide to narrow lumen, occasionally branched, straight to flexuous, interwoven, 2.2–9.2 μm in diam.

Tubes. — Generative hyphae infrequent, hyaline, thin-walled, occasionally branched, 1.9–3 μm in diam; skeletal hyphae dominant, hyaline to pale yellowish, thick-walled with a wide to narrow lumen, rarely branched, more or less straight, interwoven, 1.7–6.2 μm in diam. Cystidia absent, but fusoid cystidioles occasionally present, hyaline, thin-walled, 11.5–30.4 × 2.6–6 μm. Basidia clavate, bearing four sterigmata and a basal clamp connection, 16–20.3 × 4.8–7.2 μm; basidioles dominant, in shape similar to basidia, but smaller.

Spores. — Basidiospores oblong-ellipsoid to ellipsoid, hyaline, thin-walled, smooth, IKI–, CB–, (4.5–)4.8–5.3(–6) × (2.8–)3–3.5(–4) μm, L = 5.04 μm, W = 3.11 μm, Q = 1.60–1.65 (n = 60/2).

Type of rot. — Brown rot.

Additional specimen (paratype) examined: VIETNAM. Dam Dong Province, Da Lat, Bidoup Nui Ba National Park, on fallen trunk of Pinus kesiya, 16 October 2017, Cui 16466 (BJFC 029765).

Fomitopsis massoniana B.K. Cui, M.L. Han & Shun Liu, sp. nov. (Figures 3G,H, 7).

FIGURE 7.

Microscopic structures of Fomitopsis massoniana (drawn from the holotype). (A) Basidiospores; (B) Basidia and basidioles; (C) Cystidioles; (D) Hyphae from trama; (E) Hyphae from context. Bars: A–E = 10 μm.

MycoBank: MB 838911

Fomitopsis massoniana is characterized by its effused-reflexed to pileate basidiocarps, applanate to triquetrous or irregular pilei with buff-yellow to apricot-orange pileal surface when fresh, buff to grayish brown when dry, a white to cream pore surface when fresh, cream to buff when dry, and grows on Pinus massoniana.

Type. — CHINA. Fujian Province, Wuping County, Liangyeshan Nature Reserve, on dead tree of Pinus massoniana, 25 October 2013, Cui 11304 (Holotype, BJFC 015420).

Etymology. — Massoniana (Lat.), refers to the host tree species Pinus massoniana.

Basidiocarps. — Annual, effused-reflexed to pileate, sessile, hard corky, without odor or taste when fresh, woody hard and light in weight upon drying. Pilei applanate to triquetrous or irregular, projecting up to 4 cm long, 4.2 cm wide, 1.5 cm thick at base. Pileal surface laccate, buff-yellow to apricot-orange when fresh, becoming buff to grayish brown when dry, glabrous, sulcate, azonate; margin white to cream, obtuse. Pore surface white to cream when fresh, turning cream to buff when dry; sterile margin distinct, cream, up to 4 mm wide; pores round, 5–7 per mm, dissepiments thick, entire. Context cream to straw-yellow, woody hard, up to 0.8 cm thick. Tubes concolorous with pore surface, woody hard, up to 0.4 cm long.

Hyphal structure. — Hyphal system dimitic; generative hyphae bearing clamp connections; skeletal hyphae IKI–, CB–; tissues unchanged in KOH.

Context. — Generative hyphae infrequent, hyaline, thin- to slightly thick-walled, occasionally branched, 2–4.5 μm in diam; skeletal hyphae dominant, hyaline, thick-walled with a narrow lumen to subsolid, rarely branched, straight, interwoven, 2.2–8.2 μm in diam.

Tubes. — Generative hyphae infrequent, hyaline, thin-walled, rarely branched, 1.8–4 μm in diam; skeletal hyphae dominant, hyaline, thick-walled with a narrow lumen to narrow lumen, occasionally branched, more or less straight, interwoven, 2–7.2 μm in diam. Cystidia absent, but fusoid cystidioles occasionally present, hyaline, thin-walled, 14.8–36 × 3.8–6 μm. Basidia clavate, bearing four sterigmata and a basal clamp connection, 17–26.5 × 5.5–7.9 μm; basidioles dominant, in shape similar to basidia, but smaller.

Spores. — Basidiospores oblong-ellipsoid, hyaline, thin-walled, smooth, IKI–, CB–, (5.8–)6.2–7.3(–7.6) × (3–)3.3–4 μm, L = 6.91 μm, W = 3.53 μm, Q = 1.93–1.99 (n = 90/3).

Type of rot. — Brown rot.

Additional specimens (paratypes) examined: CHINA. Fujian Province, Wuping County, Liangyeshan Nature Reserve, on dead tree of Pinus massoniana, 25 October 2013, Cui 11288 (BJFC 015404); Wuyishan County, Longchuan Valley, on dead tree of Pinus massoniana, 16 October 2005, Cui 2848 (BJFC 000719); Guangdong Province, Fengkai County, Heishiding Nature Reserve, on fallen trunk of Pinus massoniana, 2 July 2010, Cui 9058 (BJFC 007996).

Fomitopsis subpinicola B.K. Cui, M.L. Han & Shun Liu, sp. nov. (Figures 3I,J, 8).

FIGURE 8.

Microscopic structures of Fomitopsis subpinicola (drawn from the holotype). (A) Basidiospores; (B) Basidia and basidioles; (C) Cystidioles; (D) Hyphae from trama; (E) Hyphae from context. Bars: A–E = 10 μm.

MycoBank: MB 838912

Fomitopsis subpinicola is characterized by its apricot-orange, scarlet to fuscous pileal surface when fresh, reddish brown to dark brown when dry, occasionally septated skeletal hyphae and is distributed in Northeast China.

Type. — CHINA. Heilongjiang Province, Yichun, Fenglin Nature Reserve, on fallen trunk of Pinus koraiensis, 2 August 2011, Cui 9836 (Holotype, BJFC 010729).

Etymology. — Subpinicola (Lat.), refers to the new species resembling F. pinicola in morphology.

Basidiocarps. — Annual, pileate, sessile, hard corky, without odor or taste when fresh, woody hard and light in weight upon drying. Pilei applanate, circular to sectorial, projecting up to 7.5 cm long, 8.5 cm wide, 4.5 cm thick at base. Pileal surface laccate, apricot-orange, scarlet to fuscous when fresh, becoming reddish brown to dark brown upon drying, glabrous, sulcate, azonate; margin white to cream, distinctly paler than the pileal surface, obtuse. Pore surface white to cream when fresh, turning buff yellow to buff when dry; sterile margin distinct, white to cream, up to 6 mm wide; pores round, 6–8 per mm, dissepiments thick, entire. Context cream to straw-yellow, woody hard, up to 1.2 cm thick. Tubes concolorous with pore surface, woody hard, up to 0.5 cm long.

Hyphal structure. — Hyphal system dimitic; generative hyphae bearing clamp connections; skeletal hyphae IKI–, CB–; tissues unchanged in KOH.

Context. — Generative hyphae infrequent, hyaline, thin- to slightly thick-walled, rarely branched, 2–3.2 μm in diam; skeletal hyphae dominant, yellowish brown to cinnamon brown, thick-walled with a narrow lumen to subsolid, occasionally branched, straight, interwoven, 2.2–6.8 μm in diam.

Tubes. — Generative hyphae infrequent, hyaline, thin-walled, rarely branched, 1.8–3 μm in diam; skeletal hyphae dominant, yellowish brown to cinnamon brown, thick-walled with a wide to narrow lumen, occasionally septate, without clamps, rarely branched, straight, interwoven, 1.9–6.2 μm in diam. Cystidia absent, but fusoid cystidioles occasionally present, hyaline, thin-walled, 14.5–34.6 × 3.2–7.2 μm. Basidia clavate, bearing four sterigmata and a basal clamp connection, 16–24.5 × 4.5–9 μm; basidioles dominant, in shape similar to basidia, but smaller.

Spores. — Basidiospores oblong-ellipsoid to ellipsoid, hyaline, thin-walled, smooth, IKI–, CB–, (4–)4.3–5.5(–5.9) × (2.5–)2.7–3.3(–3.5) μm, L = 4.94 μm, W = 2.97 μm, Q = 1.65–1.69 (n = 90/3).

Type of rot. — Brown rot.

Additional specimens (paratypes) examined: CHINA. Heilongjiang Province, Yichun, Fenglin Nature Reserve, on fallen trunk of Pinus koraiensis, 1 August 2011, Cui 9819 (BJFC 010712); Tangyuan County, Daliangzihe Forest Park, on living tree of Pinus koraiensis, 26 August 2008, Yuan 4912 (BJFC 015654); Inner Mongolia, Genhe, Greater Khingan Mountains Nature Reserve, on Larix, 28 August 2009, Dai 11101 (BJFC 015660), Dai 11206 (BJFC 015661); Jilin Province, Antu County, Changbaishan Nature Reserve, on fallen trunk of Betula, 7 September 2013, Dai 13480 (BJFC 014941).

Fomitopsis tianshanensis B.K. Cui & Shun Liu, sp. nov. (Figures 3K,L, 9).

FIGURE 9.

Microscopic structures of Fomitopsis tianshanensis (drawn from the holotype). (A) Basidiospores; (B) Basidia and basidioles; (C) Cystidioles; (D) Hyphae from trama; (E) Hyphae from context. Bars: A–E = 10 μm.

MycoBank: MB 838913

Fomitopsis tianshanensis is characterized by its effused-reflexed to pileate basidiocarps with soft corky texture when fresh, large pores (1–3 per mm) and long tubes (up to 2.5 cm), grows on Picea and is distributed in Tianshan Mountains Xinjiang, China.

Type. — CHINA. Xinjiang Autonomous Region, Fukang County, Tianshan Tianchi Nature Reserve, on fallen trunk of Picea schrenkiana, 4 July 2018, Cui 16821 (Holotype, BJFC 030120).

Etymology. — Tianshanensis (Lat.), refers to the species located at the Tianshan regions.

Basidiocarps. — Annual to perennial, effused-reflexed to pileate, sessile, soft corky, without odor or taste when fresh, hard corky and light in weight upon drying. Pilei applanate, semicircular to ungulate, projecting up to 11 cm long, 20 cm wide, 7 cm thick at base. Pileal surface dark bluish gray to yellowish brown when fresh, becoming fawn to deep olive when dry, slightly velutinate, small nodules appear near the base, rough, azonate; margin cream to cinnamon, obtuse to acute. Pore surface cream to pinkish buff when fresh, becoming faint yellow to light pink when dry; sterile margin distinct, cream to buff, up to 3 mm wide; pores mostly round, occasionally angular, 1–3 per mm, dissepiments thick, entire. Context cream to buff, corky, up to 3.5 cm thick. Tubes concolorous with pore surface, hard corky, up to 2.5 cm long.

Hyphal structure. — Hyphal system dimitic; generative hyphae bearing clamp connections; skeletal hyphae IKI–, CB–; tissues unchanged in KOH.

Context. — Generative hyphae infrequent, hyaline, thin- to slightly thick-walled, rarely branched, 2–4 μm in diam; skeletal hyphae dominant, yellowish brown to cinnamon brown, thick-walled with a narrow lumen to subsolid, occasionally branched, straight to flexuous, interwoven, 2.2–7.2 μm in diam.

Tubes. — Generative hyphae infrequent, hyaline, thin-walled, rarely branched, 1.9–3.2 μm in diam; skeletal hyphae dominant, hyaline to pale yellowish, thick-walled with a wide lumen, occasionally branched, straight to flexuous, 2–6.9 μm in diam, interwoven. Cystidia absent, sometimes skeletal hyphae penetrated into the hymenium, but not forming typical catahymenium; cystidioles present, fusoid, hyaline, thin-walled, 15.5–44 × 3.3–6.5 μm. Basidia clavate, bearing four sterigmata and a basal clamp connection, 17–32.5 × 4.2–9.5 μm; basidioles dominant, in shape similar to basidia, but smaller.

Spores. — Basidiospores oblong-ellipsoid, sometimes tapering at apiculus, hyaline, thin-walled, smooth, IKI–, CB–, (6–)6.3–7(–7.2) × (3–)3.2–3.8(–4) μm, L = 6.62 μm, W = 3.52 μm, Q = 1.85–1.93 (n = 90/3).

Type of rot. — Brown rot.

Additional specimens (paratypes) examined: CHINA. Xinjiang Autonomous Region, Urumqi, Nanshan Park, on fallen trunk of Picea schrenkiana, 5 July 2018, Cui 16823 (BJFC 030122), Cui 16825 (BJFC 030124), Cui 16828 (BJFC 030127); Shawan County, Lujiaowan Park, on stump of Picea schrenkiana, 6 July 2018, Cui 16830 (BJFC 030129).

Other Specimens of the Fomitopsis pinicola Complex Examined

Fomitopsis mounceae. CANADA. 3 August 2000, Teuvo Ahti 60351 (H); on Picea glauca, 25 July 1982, Tuomo Niemelä 2530 (H). UNITED STATES. On Betula, 15 September 2014, OM 18782 (H); on Tsuga heterophylla, 11 September 2014, Spirin 8367 (H).

Fomitopsis ochracea. UNITED STATES. OM 18568 (H), OM 18673 (H); on Picea, Spirin 8165 (H).

Fomitopsis schrenkii. UNITED STATES. 7 September 1992, Inkeri Ahonen 58 (BJFC 013921); Turkey Creek, Chricahua Mountain, Arizona, on Douglas fir, September 2012, Josef Vlasák 1209/61-J (BJFC 015604).

Fomitopsis pinicola. FINLAND. Helsinki, Vantaa, Tamisto Nature Reserve, on fallen trunk of Picea, 16 August 2012, Dai 12869 (BJFC 013149), Dai 12870 (BJFC 013150). ITALY. Roma, Trentino Altoadie, Trento, Molveno, on Picea, 28 April 2005, Dai 6553 (IFP). POLAND. On dead tree of Pinus, 3 October 2014, Dai 14841 (BJFC 017955); Lesser Poland Voivodeship, Gorce National Park, on Picea abies, 9 July 1985, Pekka Nuorteva (H).

Discussion

Based on the phylogenetic analyses, 10 species of the Fomitopsis pinicola complex grouped together (Figures 1, 2), including six new species from East Asia: F. abieticola, F. hengduanensis, F. kesiyae, F. massoniana, F. subpinicola, and F. tianshanensis. The main morphological characters of species in the F. pinicola complex are provided in Table 2.

TABLE 2.

A comparison of species in the Fomitopsis pinicola complex.

Species	Distribution	Basidio-	Pileal surface	Host	Pores (per mm)	Cystidia (μm)	Basidiospores		References
		carps	when fresh				L × W (μm)	Q = L/W
F. abieticola	Southwestern China	Annual to perennial; pileate	Cream to pinkish buff	Abies	2–4	17.5–50.2 × 4.3–9.5	7–9 × 4–5	1.83–1.89	This study
F. hengduanensis	High altitude areas of the Hengduan Mountains of southwestern China	Annual to perennial; pileate	Pale dark gray to reddish brown at base and cream to flesh-pink toward the margin	Picea, Pinus	6–8	13.2–36.5 × 2.5–5.4	5.2–6 × 3.2–3.6	1.57–1.63	This study
F. kesiyae	Tropical areas of Vietnam	Annual; pileate	Buff yellow to orange-yellow buff	Pinus kesiya	6–8	11.5–30.4 × 2.6–6	4.8–5.3 × 3–3.5	1.60–1.65	This study
F. massoniana	Southeastern China	Annual; effused-reflexed to pileate	Buff-yellow to apricot-orange	Pinus massoniana	5–7	14.8–36 × 3.8–6	6.2–7.3 × 3.3–4	1.85–1.9	This study
F. mounceae	Canada, northern United States	Perennial; pileate	Brownish orange to black at base and pale orange to grayish orange toward the margin	Abies, Betula, Larix, Picea, Populus, Pseudotsuga	3–5	16–35 × 3–6.5	5.8–6.6 × 3.4–4	1.7–1.9	Haight et al., 2019
F. ochracea	Canada, northern United States	Perennial; pileate	Brownish gray to grayish brown at base and orange White to pale orange toward the margin	Abies, Picea, Populus	4–5	20–40 × 4–6.5	5.1–5.9 × 3.6–4	1.3–1.4	Haight et al., 2019
F. pinicola	Europe	Perennial; pileate	Brownish orange to black at base and buff-yellow to cinnamon toward the margin	Mostly on Picea and Pinus, occasionally on other different gymnosperm or angiosperm wood	4–6	18–60 × 3–9	6–9 × 3–4.5	1.8–2.2	Ryvarden and Melo, 2014; Haight et al., 2016, 2019
F. schrenkii	Western and southwestern United States	Perennial; effused-reflexed to pileate	Grayish orange to olive brown at base and grayish orange to grayish yellow toward the margin	Abies, Picea, Pinus, Pseudotsuga	3–4	16–30 × 3–8	5.7–6.7 × 3.7–4.2	1.5–1.6	Haight et al., 2019
F. subpinicola	Northeastern China	Annual; pileate	Apricot-orange, scarlet to fuscous	Mostly on Pinus koraiensis, occasionally on Larix, Betula	6–8	14.5–34.6 × 3.2–7.2	4.3–5.5 × 2.7–3.3	1.65–1.69	This study
F. tianshanensis	Tianshan Mountains of northwestern China	Annual to perennial, effused-reflexed to pileate	Dark bluish gray to yellowish brown	Picea	1–3	15.5–44 × 3.3–6.5	6.3–7 × 3.2–3.8	1.9–1.96	This study

In the phylogenetic trees (Figures 1, 2), Fomitopsis abieticola is closely related to F. tianshanensis. Morphologically, both F. abieticola and F. tianshanensis have an annual to perennial growth habit, cream to pinkish pore surface when fresh, and large pores, but F. tianshanensis differs in its soft corky basidiocarps when fresh, and usually grows on Picea. Fomitopsis schrenkii has similar pores (3–4 per mm), but it has smaller basidia (12–22 × 6–8 μm), and slightly wider basidiospores (5.7–6.7 × 3.7–4.2 μm). Fomitopsis hengduanensis was also discovered in the Yunnan Province, but F. hengduanensis differs with smaller pores (6–8 per mm) and smaller basidiospores (5.2–6 × 3.2–3.6 μm).

Phylogenetically, Fomitopsis hengduanensis grouped together with F. kesiyae (Figures 1, 2). Morphologically, F. hengduanensis and F. kesiyae share a white to cream pore surface when fresh and have similar pores, but F. kesiyae differs in having a buff yellow to orange-yellow buff pileal surface when fresh, reddish brown to yellowish brown when dry, and grows on the Pinus kesiya tree. Fomitopsis pinicola, F. schrenkii and F. mounceae all have similar pilei, but they have larger pores (4–6 per mm in F. pinicola, 3–4 per mm in F. schrenkii, 3–5 per mm in F. mounceae; Table 2). Fomitopsis subpinicola has similar sized pores, but it has smaller basidia (16.1–24.5 × 4.5–9 μm) and basidiospores (4.3–5.5 × 2.7–3.3 μm) and is distributed in south northeast China.

Fomitopsis kesiyae was described from Vietnam on the tree of Pinus kesiya. Phylogenetically, two sampled specimens of F. kesiyae formed a high supported lineage (99% ML, 99% MP, 1.00 BPP) and are closely related to F. hengduanensis (Figures 1, 2). However, F. hengduanensis differs in having larger basidia (16.6–34.5 × 5.4–10.2 μm) and basidiospores (5.2–6 × 3.2–3.6 μm). Fomitopsis subpinicola has similar sized pores (6–8 per mm) and basidiospores (4.3–5.5 × 2.7–3.3 μm), but it has an apricot-orange, scarlet to fuscous pileal surface when fresh, and is reddish brown to dark brown when dry. Fomitopsis massoniana has a similar colored pileal surface when fresh and similar sized pores (5–7 per mm), but it has larger basidiospores (6.2–7.3 × 3.3–4 μm) and grows on Pinus massoniana rather than Pinus kesiya.

Morphologically, Fomitopsis massoniana is similar to F. kesiyae; both species have an annual growth habit and a similar colored pileal surface when fresh. However, F. kesiyae differs in having smaller basidiospores (4.8–5.3 × 3–3.5 μm), is distributed in Vietnam, and grows on Pinus kesiya. Fomitopsis hengduanensis has similar sized pores (6–8 per mm), but compared to F. massoniana, F. hengduanensis has larger sized basidiocarps, a laccate pileal surface with pale dark gray to reddish brown at base and cream to flesh-pink toward the margin when fresh, and smaller sized basidiospores (5.2–6 × 3.2–3.6 μm). Phylogenetically, these two species are distinct from each other (Figures 1, 2). Fomitopsis massoniana is closely related to F. subpinicola, they share a cream to buff pore surface and have similar sized pores, but F. subpinicola has smaller basidiospores (4.3–5.5 × 2.7–3.3 μm).

Fomitopsis subpinicola can be easily separated from F. pinicola by its apricot-orange, scarlet to fuscous pileal surface when fresh, reddish brown to dark brown when dry, smaller basidiospores (4.3–5.5 × 2.7–3.3 μm) and is located in the Northeast of China. Phylogenetically, F. subpinicola is closely related to F. massoniana. Morphologically, F. subpinicola is similar to F. massonian, which has an annual growth habit and white to cream pore surface when fresh. But F. massoniana differs by its effused-reflexed to pileate basidiocarps, lager basidiospores (6.2–7.3 × 3.3–4 μm) and grows on the Pinus massoniana tree. Fomitopsis hengduanensis and F. kesiyae have similar sized pores (6–8 per mm), but F. hengduanensis has larger sized basidia (16.6–34.5 × 5.4–10.2 μm), F. kesiyae has a buff yellow to orange-yellow buff pileal surface when fresh, reddish brown to yellowish brown when dry, and grows on the Pinus kesiya tree.

Phylogenetically, specimens of Fomitopsis tianshanensis formed a well-supported lineage (Figures 1, 2) and are grouped with F. abieticola. But F. abieticola differs from F. tianshanensis in having large sized cystidioles (17.5–50.2 × 4.3–9.5 μm), basidia (20.8–40.5 × 5.5–11.5 μm), and basidiospores (7–9 × 4–5 μm). Fomitopsis pinicola also grows mainly on Picea, but it has smaller pores (4–6 per mm), a brownish orange to black pileal surface at base and buff-yellow to cinnamon toward the margin when fresh, and is distributed in Europe.

Previously, Fomitopsis pinicola was used as a broad species concept, specimens from Europe, North America, and East Asia were all identified as F. pinicola based on morphological characters (Gilbertson and Ryvarden, 1986; Ryvarden and Gilbertson, 1993; Núñez and Ryvarden, 2001; Dai, 2012; Ryvarden and Melo, 2014). Recent phylogenetic analyses indicated that F. pinicola is a species complex and represent several different species. Haight et al. (2016) proposed four well-supported clades: one lineage F. pinicola sensu stricto from Europe and three lineages from North America. Subsequently, Haight et al. (2019) identified these three lineages as F. mounceae, F. ochracea, and F. schrenkii from North America, and F. pinicola is restricted to Eurasia and does not occur in North America. In the current study, samples previously identified as F. pinicola from China and Vietnam in East Asia represent six distinct species. Furthermore, our results indicated that species of the F. pinicola complex usually have limited distribution areas and host specialization. In East Asia, F. abieticola is distributed in southwestern China and grows on Abies; F. hengduanensis is distributed in high altitude areas of the Hengduan Mountains of southwestern China, and it mostly grows on Picea, occasionally on other gymnosperm wood; F. kesiyae is distributed in tropical areas of Vietnam and grows only on Pinus kesiya; F. massoniana is distributed in southeastern China and grows only on Pinus massoniana; F. subpinicola was found in northeastern China and grows mainly on Pinus koraiensis, occasionally on other gymnosperm or angiosperm wood; F. tianshanensis is distributed in Tianshan Mountains of northwestern China and only grows on Picea schrenkiana. In Europe, F. pinicola is widespread, and it mostly grows on Picea and Pinus, occasionally on other different gymnosperm or angiosperm wood (Ryvarden and Melo, 2014). In North America, F. mounceae and F. ochracea is distributed in Canada and the northern United States, and they grow on different gymnosperm or angiosperm wood (Ryvarden and Stokland, 2008; Haight et al., 2019); F. schrenkii is distributed in western and southwestern regions of the United States and mostly grows on different gymnosperm wood, rarely on angiosperm wood (Haight et al., 2019). Among the wood-rotting fungi, some other polypore genera also have limited distribution areas and host specializations, such as Bondarzewia Singer (Song et al., 2016), Heterobasidion Bref. (Chen et al., 2015; Yuan et al., 2020), Laetiporus Murrill (Song and Cui, 2017), and Sanghuangporus Sheng H. Wu, L.W. Zhou & Y.C. Dai (Zhu et al., 2019).

Key to Accepted Species of Fomitopsis pinicola Complex

1.	Distribution in East Asia	2
1.	Distribution in North America or Europe	7
2.	Pores < 5 per mm	3
2.	Pores 5–8 per mm	4
3.	Basidiospores oblong-ellipsoid to ellipsoid, 7–9 × 4–5 μm	F. abieticola
3.	Basidiospores oblong-ellipsoid, 6.3–7 × 3.2–3.8 μm	F. tianshanensis
4.	Distribution in tropical areas	F. kesiyae
4.	Distribution in temperate areas	5
5.	Basidiocarps annual to perennial; pileal surface cream to flesh-pink toward the margin when fresh	F. hengduanensis
5.	Basidiocarps annual; pileal surface white to cream toward the margin when fresh	6
6.	Basidiospores oblong-ellipsoid, 6.2–7.3 × 3.3–4 μm	F. massoniana
6.	Basidiospores oblong-ellipsoid to ellipsoid, 4.3–5.5 × 2.7–3.3 μm	F. subpinicola
7.	Pilei never with reddish brown band	F. ochracea
7.	Pilei with reddish brown band	8
8.	Distribution in Europe; basidia < 20 μm long	F. pinicola
8.	Distribution in North America; basidia > 20 μm long	9
9.	Basidiospores ellipsoid to cylindrical, Q = 1.6–1.9	F. mounceae
9.	Basidiospores ellipsoid to broadly cylindrical, Q = 1.5–1.6	F. schrenkii

Data Availability Statement

The datasets presented in this study can be found in an online repository. The name of the repository and accession number can be found below: https://treebase.org/treebase-web/search/study/summary.html?id=27994&x-access-code=ab2495717aaf081f0557e6680c381710&agreement=ok, submission ID: 27994.

Author Contributions

B-KC and SL designed the experiment. SL, M-LH, D-MW, and B-KC prepared the samples. SL, T-MX, and YW conducted the molecular experiments and analyzed the data. SL, D-MW, and B-KC drafted the manuscript. All the authors approved the manuscript.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Abbreviations

BI

Bayesian inference

BJFC

Herbarium of the Institute of Microbiology, Beijing Forestry University

BGI

Beijing Genomics Institute

BPP

Bayesian posterior probabilities

BT

Bootstrap

CB

Cotton Blue

CB–

acyanophilous

GTR + I + G

General time reversible + proportion invariant + gamma

IKI

Melzer’s reagent

IKI–

neither amyloid nor dextrinoid

ILD

incongruence length difference test

ITS

internal transcribed spacer

KOH

5% potassium hydroxide

L

mean spore length (arithmetic average of all spores)

ML

maximum likelihood

MP

maximum parsimony

MPT

most parsimonious tree

n (a/b)

number of spores (a) measured from given number (b) of specimens

Q

variation in the L/W ratios between the specimens studied

RPB2

DNA-directed RNA polymerase II subunit 2

TL

tree length

W

mean spore width (arithmetic average of all spores)

CI

consistency index

RI

retention index

RC

rescaled consistency index

HI

homoplasy index

TEF

translation elongation factor 1-α.