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Research Article
Species diversity, molecular phylogeny and ecological habits of Cyanosporus (Polyporales, Basidiomycota) with an emphasis on Chinese collections
expand article infoShun Liu, Tai-Min Xu, Chang-Ge Song, Chang-Lin Zhao§, Dong-Mei Wu|, Bao-Kai Cui
‡ Beijing Forestry University, Beijing, China
§ Southwest Forestry University, Kunming, China
| Biotechnology Research Institute, Xinjiang Academy of Agricultural and Reclamation Sciences, Shihezi, China
Open Access

Abstract

Cyanosporus is a genus widely distributed in Asia, Europe, North America, South America and Oceania. It grows on different angiosperm and gymnosperm trees and can cause brown rot of wood. Blue-tinted basidiomata of Cyanosporus makes it easy to distinguish from other genera, but the similar morphological characters make it difficult to identify species within the genus. Phylogeny and taxonomy of Cyanosporus were carried out based on worldwide samples with an emphasis on Chinese collections, and the species diversity of the genus is updated. Four new species, C. flavus, C. rigidus, C. subungulatus and C. tenuicontextus, are described based on the evidence of morphological characters, distribution areas, host trees and molecular phylogenetic analyses inferred from the internal transcribed spacer (ITS) regions, the large subunit of nuclear ribosomal RNA gene (nLSU), the small subunit of nuclear ribosomal RNA gene (nSSU), the small subunit of mitochondrial rRNA gene (mtSSU), the largest subunit of RNA polymerase II (RPB1), the second largest subunit of RNA polymerase II (RPB2), and the translation elongation factor 1-α gene (TEF). Our study expanded the number of Cyanosporus species to 35 around the world including 23 species from China. Detailed descriptions of the four new species and the geographical locations of the Cyanosporus species in China are provided.

Keywords

brown-rot fungi, distribution areas, host trees, multi-gene phylogeny, new species

Introduction

Cyanosporus was proposed as a monotypic genus for Polyporus caesius (Schrad.) Fr. based on its cyanophilous basidiospores (McGinty 1909). However, Tyromyces caesius (Schrad.) Murrill and Postia caesia (Schrad.) P. Karst. were frequently used instead of Cyanosporus caesius (Schrad.) McGinty in subsequent studies (Donk 1960; Jahn 1963; Lowe 1975). Later, four species in the Postia caesia complex were described from Europe, viz., P. luteocaesia (A. David) Jülich, P. subcaesia (A. David) Jülich, P. alni Niemelä & Vampola and P. mediterraneocaesia M. Pieri & B. Rivoire (David 1974, 1980; Jahn 1979; Pieri and Rivoire 2005). Then, the subgenus Cyanosporus (McGinty) V. Papp was proposed for the species of P. caesia complex (Papp 2014). Miettinen et al. (2018) revised the species concept of the P. caesia complex based on morphology and two gene markers (ITS and TEF) and raised the species number of the complex to 24, including six species from China.

Previously, species identification of the P. caesia complex was only based on morphological characters and host trees in China, and only two species were recorded from China before Dai (2012), viz., P. alni and P. caesia. Recently, taxonomic studies of P. caesia complex in China have been carried out, and some new species have been described based on both morphological characteristics and molecular data. Shen et al. (2019) carried out a comprehensive study on Postia and related genera, in which Cyanosporus was supported as an independent genus with 12 species were accepted in this genus. Liu et al. (2021a) studied the species diversity and molecular phylogeny of Cyanosporus and the number of Cyanosporus species was expanded to 31 around the world, including 19 species from China. These studies have greatly enriched the species of Cyanosporus in China. Currently, the morphological characteristics of the genus are as follows: basidiomata annual, pileate or resupinate to effused-reflexed, soft corky, corky to fragile. Pileal surface white to cream to greyish brown, usually with blue tint. Pore surface white to cream, frequently bluish; pores round to angular. Context white to cream, corky. Tubes cream, fragile. Hyphal system monomitic; generative hyphae clamped, IKI–, CB–. Cystidia usually absent, cystidioles occasionally present. Basidiospores narrow, allantoid to cylindrical, hyaline, usually slightly thick-walled, smooth, IKI–, weakly CB+.

Cyanosporus species usually have blue-tinted basidiomata, which makes it easy to recognize. Some specimens with blue-tinted basidiomata were collected during investigations into the diversity of polypores in China, and four undescribed species of Cyanosporus were discovered. To confirm the affinity of the undescribed species to Cyanosporus, phylogenetic analyses were carried out based on the combined datasets of ITS+TEF and ITS+nLSU+nSSU+mtSSU+RPB1+RPB2+TEF sequences. During the investigation and study of Cyanosporus, the information of host trees and distribution areas of species in the genus from China were also obtained (Table 1). Four new species are described and illustrated in the current study, and the geographical locations of the Cyanosporus species distributed in China are indicated on the map (Fig. 1).

Table 1.

The main ecological habits of Cyanosporus with an emphasis on distribution areas and host trees. New species are shown in bold.

Species Distribution in the world Distribution in China Climate zone Host Reference
C. alni (Niemelä & Vampola) B.K. Cui, L.L. Shen & Y.C. Dai Europe (Czech Republic, Denmark, Finland, Germany, Norway, Poland, Russia, Slovakia), East Asia (China) Guizhou, Hebei Temperate Angiosperm (Alnus, Betula, Corylus, Fagus, Populus, Quercus) Miettinen et al. 2018; present study
C. arbuti (Spirin) B.K. Cui & Shun Liu North America (USA) Temperate Angiosperm (Arbutus) Miettinen et al. 2018
C. auricomus (Spirin & Niemelä) B.K. Cui & Shun Liu Europe (Finland, Poland, Russia), East Asia (China) Inner Mongolia Temperate to boreal Gymnosperm (Pinus, Picea) Miettinen et al. 2018; Liu et al. 2021a
C. bifarius (Spirin) B.K. Cui & Shun Liu Europe (Russia), East Asia (China, Japan) Jilin, Sichuan, Yunnan Cold temperate Gymnosperm (Picea, Pinus, Larix) Miettinen et al. 2018; present study
C. bubalinus B.K. Cui & Shun Liu East Asia (China) Yunnan Temperate Gymnosperm (Pinus) Liu et al. 2021a
C. caesiosimulans (G.F. Atk.) B.K. Cui & Shun Liu Europe (Finland, Russia), North America (USA) Temperate Angiosperm (Corylus, Fagus, Populus) and gymnosperm (Abies, Picea) Miettinen et al. 2018
C. caesius (Schrad.) McGinty Europe (Czech Republic, Denmark, Finland, France, Germany, Russia, Slovakia, Spain, UK) Common in temperate, rare in south boreal zone Angiosperm (Betula, Fagus, Salix) and gymnosperm (Abies, Picea) Miettinen et al. 2018
C. coeruleivirens (Corner) B.K. Cui, Shun Liu & Y.C. Dai Asia (China, Indonesia), Europe (Russia) Hunan, Jilin, Zhejiang Warm temperate Angiosperm (Tilia, Ulmus) Miettinen et al. 2018; present study
C. comatus (Miettinen) B.K. Cui & Shun Liu North America (USA), East Asia (China) Sichuan, Xizang Temperate Angiosperm (Acer) and gymnosperm (Abies, Picea, Tsuga) Miettinen et al. 2018; present study
C. cyanescens (Miettinen) B.K. Cui & Shun Liu Europe (Estonia, Finland, France, Poland, Russia, Spain, Sweden) Temperate to Mediterranean mountains Gymnosperm (Abies, Picea, Pinus) Miettinen et al. 2018
C. flavus B.K. Cui & Shun Liu East Asia (China) Sichuan Plateau humid climate Gymnosperm (Abies, Picea) Present study
C. fusiformis B.K. Cui, L.L. Shen & Y.C. Dai East Asia (China) Guizhou, Sichuan North temperate to subtropical Angiosperm (Rhododendron) Shen et al. 2019
C. glauca (Spirin & Miettinen) B.K. Cui & Shun Liu East Asia (China), Europe (Russia) Jilin Cold temperate mountains Gymnosperm (Abies, Picea) Miettinen et al. 2018
C. gossypinus (Moug. & Lév.) B.K. Cui & Shun Liu Europe (France) Temperate Gymnosperm (Cedrus) Miettinen et al. 2018
C. hirsutus B.K. Cui & Shun Liu East Asia (China) Qinghai, Sichuan, Yunnan Temperate to plateau continental climate Gymnosperm (Abies, Picea) Liu et al. 2021a; present study
C. livens (Miettinen & Vlasák) B.K. Cui & Shun Liu North America (Canada, USA) Temperate Angiosperm (Acer, Betula, Fagus) and gymnosperm (Abies, Larix, Picea, Tsuga) Miettinen et al. 2018
C. luteocaesius (A. David) B.K. Cui, L.L. Shen & Y.C. Dai Europe (France) Mediterranean Gymnosperm (Pinus) Miettinen et al. 2018
C. magnus (Miettinen) B.K. Cui & Shun Liu East Asia (China) Chongqin, Jilin, Hainan, Yunnan Temperate Angiosperm (Populus) and gymnosperm (Cunninghamia) Miettinen et al. 2018; present study
C. mediterraneocaesius
(M. Pieri & B. Rivoire) B.K. Cui, L.L. Shen & Y.C. Dai
Europe (France, Spain) Warm temperate to Mediterranean Angiosperm (Buxus, Erica, Populus, Quercus) and gymnosperm (Cedrus, Juniperus, Pinus) Miettinen et al. 2018
C. microporus B.K. Cui, L.L. Shen & Y.C. Dai East Asia (China) Yunnan subtropical Angiosperm (undetermined) Shen et al. 2019
C. nothofagicola B.K. Cui, Shun Liu & Y.C. Dai Oceania (Australia), South America (Argentina) Temperate marine climate Angiosperm (Nothofagus) Liu et al. 2021a
C. piceicola B.K. Cui, L.L. Shen & Y.C. Dai East Asia (China) Sichuan, Xizang, Yunnan Warm temperate to subtropical Gymnosperm (Picea) Shen et al. 2019
C. populi (Miettinen) B.K. Cui & Shun Liu East Asia (China), Europe (Finland, Norway, Poland, Russia), North America (USA) Qinghai, Jilin, Sichuan, Yunnan Boreal to temperate Angiosperm (Acer, Alnus, Betula, Populus, Salix) and gymnosperm (Picea) Miettinen et al. 2018; Liu et al. 2021a; present study
C. rigidus B.K. Cui & Shun East Asia (China) Yunnan Warm temperate Gymnosperm (Picea) Present study
C. simulans (P. Karst.) B.K. Cui & Shun Liu East Asia (China), Europe (Estonia, Finland, France, Germany, Norway, Russia), North America (Canada, USA) Jilin Warm temperate to boreal Angiosperm (Corylus, Fagus, Populus, Sorbus, Ulmus) and gymnosperm (Abies, Cedrus, Juniperus, Picea, Pinus, Thuja, Tsuga) Miettinen et al. 2018
C. subcaesius (A. David) B.K. Cui, L.L. Shen & Y.C. Dai Europe (Czech Republic, Finland, France, Russia, UK) Temperate Angiosperm (Alnus, Carpinus, Crataegus, Corylus, Fagus, Fraxinus, Malus, Populus, Prunus, Quercus, Salix, Ulmus) Miettinen et al. 2018
C. subhirsutus B.K. Cui, L.L. Shen & Y.C. Dai East Asia (China) Guizhou, Fujian, Yunnan Warm temperate to subtropical Angiosperm (Pterocarya) Shen et al. 2019
C. submicroporus B.K. Cui & Shun Liu East Asia (China) Sichuan, Yunnan, Zhejiang Alpine plateau to subtropical Angiosperm (Alnus, Cyclobalanopsis) Liu et al. 2021a; present study
C. subungulatus B.K. Cui & Shun Liu East Asia (China) Yunnan Subtropical Angiosperm (undetermined) and gymnosperm (Pinus) Present study
C. subviridis (Ryvarden & Guzmán) B.K. Cui & Shun Liu Europe (Finland), North America (Mexico, USA) Temperate to boreal Gymnosperm (Abies, Picea, Pinus) Miettinen et al. 2018
C. tenuicontextus B.K. Cui & Shun Liu East Asia (China) Yunnan Subtropical Angiosperm (undetermined) and gymnosperm (Pinus) Present study
C. tenuis B.K. Cui, Shun Liu & Y.C. Dai East Asia (China) Sichuan Subtropical monsoon to Alpine plateau Gymnosperm (Picea) Liu et al. 2021a
C. tricolor B.K. Cui, L.L. Shen & Y.C. Dai East Asia (China) Sichuan, Xizang Alpine plateau Gymnosperm (Abies, Picea) Shen et al. 2019
C. ungulatus B.K. Cui, L.L. Shen & Y.C. Dai East Asia (China) Sichuan Subtropical monsoon to Alpine plateau Angiosperm (Castanopsis) and gymnosperm (Abies) Shen et al. 2019
C. yanae (Miettinen & Kotir.) B.K. Cui & Shun Liu Europe (Russia) Temperate continental climate Gymnosperm (Larix, Pinus) Miettinen et al. 2018
Figure 1. 

The geographical locations of the Cyanosporus species distributed in China.

Materials and methods

Morphological studies

The examined specimens were deposited in the herbarium of the Institute of microbiology, Beijing Forestry University (BJFC), and some duplicates were deposited at the Institute of Applied Ecology, Chinese Academy of Sciences, China (IFP) and Southwest Forestry University (SWFC). Macro-morphological descriptions were based on the field notes and measurements of herbarium specimens. Special colour terms followed Petersen (1996). Micro-morphological data were obtained from the dried specimens and observed under a light microscope following Cui et al. (2019) and Liu et al. (2021b). Sections were studied at a magnification up to × 1000 using a Nikon Eclipse 80i microscope and phase contrast illumination (Nikon, Tokyo, Japan). Drawings were made with the aid of a drawing tube. Microscopic features, measurements and drawings were made from slide preparations stained with Cotton Blue and Melzer’s reagent. Spores were measured from sections cut from the tubes. To present variation in the size of basidiospores, 5% of measurements were excluded from each end of the range and extreme values are given in parentheses.

In the text the following abbreviations were used: IKI = Melzer’s reagent, IKI– = neither amyloid nor dextrinoid, KOH = 5% potassium hydroxide, CB = Cotton Blue, CB + = cyanophilous, CB – = acyanophilous, L = mean spore length (arithmetic average of all spores), W = mean spore width (arithmetic average of all spores), Q = variation in the L/W ratios between the specimens studied, n (a/b) = number of spores (a) measured from given number (b) of specimens.

Molecular studies and phylogenetic analysis

A cetyl trimethylammonium bromide (CTAB) rapid plant genome extraction kit-DN14 (Aidlab Biotechnologies Co., Ltd, Beijing, China) was used to extract total genomic DNA from dried specimens, and performed the polymerase chain reaction (PCR) according to the manufacturer’s instructions with some modifications as described by Shen et al. (2019) and Liu et al. (2021a). The ITS regions were amplified with primer pairs ITS5 and ITS4 (White et al. 1990). The nLSU regions were amplified with primer pairs LR0R and LR7 (http://www.biology.duke.edu/fungi/mycolab/primers.htm). The nSSU regions were amplified with primer pairs NS1 and NS4 (White et al. 1990). The mtSSU regions were amplified with primer pairs MS1 and MS2 (White et al. 1990). RPB1 was amplified with primer pairs RPB1-Af and RPB1-Cr (Matheny et al. 2002). RPB2 was amplified with primer pairs fRPB2-f5F and bRPB2-7.1R (Matheny 2005). Part of TEF was amplified with primer pairs EF1-983 F and EF1-1567R (Rehner 2001).

The PCR cycling schedule for ITS, mtSSU and TEF included an initial denaturation at 95 °C for 3 min, followed by 35 cycles at 94 °C for 40 s, 54 °C for ITS and mtSSU, 54–55 °C for TEF for 45 s, 72 °C for 1 min, and a final extension at 72 °C for 10 min. The PCR cycling schedule for nLSU and nSSU included an initial denaturation at 94 °C for 1 min, followed by 35 cycles at 94 °C for 30 s, 50 °C for nLSU and 52 °C for nSSU for 1 min, 72 °C for 1.5 min, and a final extension at 72 °C for 10 min. The PCR procedure for RPB1 and RPB2 follow Justo and Hibbett (2011) with slight modifications: initial denaturation at 94 °C for 2 min, followed by 10 cycles at 94 °C for 40 s, 60 °C for 40 s and 72 °C for 2 min, then followed by 37 cycles at 94 °C for 45 s, 55 °C for 1.5 min and 72 °C for 2 min, and a final extension of 72 °C for 10 min. The PCR products were purified and sequenced at Beijing Genomics Institute (BGI), China, with the same primers. All newly generated sequences were deposited at GenBank (Table 1).

Additional sequences were downloaded from GenBank (Table 1). All sequences of ITS, nLSU, nSSU, mtSSU, RPB1, RPB2 and TEF were respectively aligned in MAFFT 7 (Katoh and Standley 2013; http://mafft.cbrc.jp/alignment/server/) 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’’. The final concatenated sequence alignment was deposited at TreeBase (http://purl.org/phylo/treebase; submission ID: 29010).

Most parsimonious phylogenies were inferred from the combined 2-gene dataset (ITS+TEF) and 7-gene dataset (ITS+nLSU+nSSU+mtSSU+RPB1+RPB2+TEF), and their congruences 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. Phylogenetic analyses approaches followed Liu et al. (2019) and Sun et al. (2020). In phylogenetic reconstruction, the sequences of Antrodia serpens (Fr.) Donk and A. tanakae (Murrill) Spirin & Miettinen obtained from GenBank were used as outgroups. Maximum parsimony analysis was applied to the combined multiple genes datasets, and the tree construction procedure was performed in PAUP* version 4.0b10. All characters were equally weighted and gaps were treated as missing data. Trees were inferred using the heuristic search option with TBR branch swapping and 1000 random sequence additions. Max-trees were set to 5000, branches of zero length were collapsed and all parsimonious trees were saved. Clade robustness was assessed using a bootstrap (BT) analysis with 1000 replicates (Felsenstein 1985). Descriptive tree statistics tree length (TL), consistency index (CI), retention index (RI), rescaled consistency index (RC), and homoplasy index (HI) were calculated for each most Parsimonious Tree (MPT) generated. RAxmL v.7.2.8 was used to construct a maximum likelihood (ML) tree with a GTR+G+I model of site substitution including estimation of Gamma-distributed rate heterogeneity and a proportion of invariant sites (Stamatakis 2006). The branch support was evaluated with a bootstrapping method of 1000 replicates (Hillis and Bull 1993). The phylogenetic tree was visualized using FigTree v1.4.2 (http://tree.bio.ed.ac.uk/software/figtree/).

MrModeltest 2.3 (Posada and Crandall 1998; Nylander 2004) was used to determine the best-fit evolution model for the combined multi-gene dataset for Bayesian inference (BI). Bayesian inference was calculated with MrBayes 3.1.2 with a general time reversible (GTR) model of DNA substitution and a gamma distribution rate variation across sites (Ronquist and Huelsenbeck 2003). Four Markov chains were run for 2 runs from random starting trees for 1.8 million generations (ITS+TEF), for 3.5 million generations (ITS+nLSU+nSSU+mtSSU+RPB1+RPB2+TEF) and trees were sampled every100 generations. The first one-fourth generations were discarded as burn-in. A majority rule consensus tree of all remaining trees was calculated. Branches that received bootstrap support for maximum parsimony (MP), maximum likelihood (ML) and Bayesian posterior probabilities (BPP) greater than or equal to 75% (MP and ML) and 0.95 (BPP) were considered as significantly supported, respectively.

Results

Phylogeny

The combined 2-gene (ITS+TEF) sequences dataset had an aligned length of 1015 characters, of which 502 characters were constant, 62 were variable and parsimony-uninformative, and 451 were parsimony-informative. MP analysis yielded 10 equally parsimonious trees (TL = 2396, CI = 0.379, RI = 0.735, RC = 0.279, HI = 0.621). The best model for the concatenate sequence dataset estimated and applied in the Bayesian inference was GTR+I+G with equal frequency of nucleotides. ML analysis resulted in a similar topology as MP and Bayesian analyses, and only the ML topology is shown in Fig. 2.

Figure 2. 

Maximum likelihood tree illustrating the phylogeny of Cyanosporus and its related genera in the antrodia clade based on the combined sequences dataset of ITS+TEF. Branches are labelled with maximum likelihood bootstrap higher than 50%, parsimony bootstrap proportions higher than 50% and Bayesian posterior probabilities more than 0.90 respectively. Bold names = New species.

The combined 7-gene (ITS+nLSU+nSSU+mtSSU+RPB1+RPB2+TEF) sequences dataset had an aligned length of 5634 characters, of which 3843 characters were constant, 247 were variable and parsimony-uninformative, and 1544 were parsimony-informative. MP analysis yielded 23 equally parsimonious trees (TL = 5756, CI = 0.468, RI = 0.752, RC = 0.352, HI = 0.532). The best model for the concatenate sequence dataset estimated and applied in the Bayesian inference was GTR+I+G with equal frequency of nucleotides. ML analysis resulted in a similar topology as MP and Bayesian analyses, and only the ML topology is shown in Fig. 3.

Figure 3. 

Maximum likelihood tree illustrating the phylogeny of Cyanosporus and its related genera in the antrodia clade based on the combined sequences dataset of ITS+nLSU+nSSU+mtSSU+RPB1+RPB2+TEF. Branches are labelled with maximum likelihood bootstrap higher than 50%, parsimony bootstrap propwortions higher than 50% and Bayesian posterior probabilities more than 0.90 respectively. Bold names = New species.

The phylogenetic trees inferred from ITS+TEF and ITS+nLSU+nSSU+mtSSU+RPB1+RPB2+TEF gene sequences were all obtained from 106 fungal samples representing 65 taxa of Cyanosporus and its related genera within the antrodia clade. 74 samples representing 35 taxa of Cyanosporus clustered together and separated from species of Postia and other related genera. As for Cyanosporus, the sequences used in phylogenetic analyses include 28 holotype specimen sequences, one isotype specimen sequence and one neotype specimen sequence (Table 1).

Taxonomy

Cyanosporus flavus B.K. Cui & Shun Liu, sp. nov.

MycoBank No: 842319
Figs 4, 5

Diagnosis

Cyanosporus flavus is characterised by flabelliform to semicircular and hirsute pileus with ash grey to light vinaceous grey pileal surface when fresh, buff to lemon-chrome pore surface when dry, and allantoid and slightly curved basidiospores (4.6–5.2 × 0.8–1.3 μm).

Holotype

China. Sichuan Province, Jiuzhaigou County, on stump of Picea sp., 19.IX.2020, Cui 18547 (BJFC 035408).

Etymology

Flavus (Lat.): referring to its lemon-chrome pore surface when dry.

Fruiting body

Basidiomata annual, pileate, soft and watery, without odour or taste when fresh, becoming corky to fragile and light in weight upon drying. Pileus flabelliform to semicircular, projecting up to 3.2 cm, 5.7 cm wide and 0.9 cm thick at base. Pileal surface ash-grey to light vinaceous grey when fresh, becoming pale mouse-grey to mouse-grey when dry, hirsute; margin acute to slightly obtuse, white with a little blue tint when fresh, olivaceous buff to greyish brown when dry. Pore surface white to cream when fresh, becoming buff to lemon-chrome when dry; sterile margin narrow to almost lacking; pores angular, 5–7 per mm; dissepiments thin, entire to lacerate. Context white to cream, soft corky, up to 6 mm thick. Tubes pale mouse-grey to ash-grey, fragile, up to 4 mm long.

Hyphal structure

Hyphal system monomitic; generative hyphae with clamp connections, IKI–, CB–; hyphae unchanged in KOH.

Context

Generative hyphae hyaline, thin- to slightly thick-walled with a wide lumen, occasionally branched, loosely interwoven, 2.7–6.5 μm in diam.

Tubes

Generative hyphae hyaline, thin- to slightly thick-walled with a wide lumen, rarely branched, interwoven, 2.2–4.7 μm in diam. Cystidia absent; cystidioles present, fusoid, thin-walled, 12.3–17.8 × 2.2–3.5 μm. Basidia clavate, bearing four sterigmata and a basal clamp connection, 13.2–16.5 × 3.2–5.5 μm; basidioles dominant, in shape similar to basidia, but smaller, 12.6–15.7 × 2.9–5.2 μm.

Figure 4. 

Basidiomata of Cyanosporus flavus (Holotype, Cui 18547). Scale bar: 1 cm. The upper figure is the upper surface and the lower figure is the lower surface of the basidiomata.

Figure 5. 

Microscopic structures of Cyanosporus flavus (Holotype, Cui 18547) a basidiospores b basidia and basidioles c cystidioles d hyphae from trama e hyphae from context. Drawings by: Shun Liu.

Spores

Basidiospores slim allantoid, slightly curved, hyaline, thin- to slightly thick-walled, smooth, IKI–, CB–, 4.6–5.2 × 0.8–1.3 μm, L = 5 μm, W = 0.99 μm, Q = 4.96–5.25 (n = 60/2).

Type of rot

Brown rot.

Additional specimen (paratype) examined

China. Sichuan Province, Jiuzhaigou County, Jiuzhaigou Nature Reserve, on fallen trunk of Abies sp., 20.IX.2020, Cui 18562 (BJFC 035423).

Cyanosporus rigidus B.K. Cui & Shun Liu, sp. nov.

MycoBank No: 842320
Figs 6, 7

Diagnosis

Cyanosporus rigidus is characterised by corky, hard corky to rigid basidiomata with a buff yellow to clay-buff and tomentose pileal surface when fresh, becoming olivaceous buff to greyish brown when dry, smaller and cylindrical to allantoid basidiospores (3.7–4.2 × 0.9–1.3 μm).

Holotype

China. Yunnan Province, Yulong County, Laojun Mountain, Jiushijiu Longtan, on fallen trunk of Abies sp., 15.IX.2018, Cui 17032 (BJFC 030331).

Etymology

Rigidus (Lat.): referring to the rigid basidiomata.

Fruiting body

Basidiomata annual, pileate, corky, without odour or taste when fresh, becoming hard corky to rigid upon drying. Pileus flabelliform, projecting up to 1.6 cm, 3.8 cm wide and 0.6 cm thick at base. Pileal surface tomentose, buff yellow to clay-buff, when fresh, becoming smooth, rugose, olivaceous buff to greyish brown when dry; margin obtuse. Pore surface white to cream when fresh, becoming buff-yellow to pinkish buff when dry; sterile margin narrow to almost lacking; pores angular, 5–8 per mm; dissepiments thin, entire to lacerate. Context cream to buff, hard corky, up to 4 mm thick. Tubes cream to pinkish buff, brittle, up to 5 mm long.

Figure 6. 

Basidiomata of Cyanosporus rigidus (Holotype, Cui 17032). Scale bar: 1.5 cm. The upper figure is the upper surface and the lower figure is the lower surface of the basidiomata.

Figure 7. 

Microscopic structures of Cyanosporus rigidus (Holotype, Cui 17032) a basidiospores b basidia and basidioles c hyphae from trama d hyphae from context. Drawings by: Shun Liu.

Hyphal structure

Hyphal system monomitic; generative hyphae with clamp connections, IKI–, CB–; hyphae unchanged in KOH.

Context

Generative hyphae hyaline, thin- to slightly thick-walled with a wide lumen, rarely branched, loosely interwoven, 2.2–5 μm in diam.

Tubes

Generative hyphae hyaline, thin- to slightly thick-walled with a wide lumen, occasionally branched, interwoven, 2–4 μm in diam. Cystidia and cystidioles absent. Basidia clavate, bearing four sterigmata and a basal clamp connection, 12.4–14.8 × 3–4.2 μm; basidioles dominant, in shape similar to basidia, but smaller, 11.8–13.9 × 2.6–4 μm.

Spores

Basidiospores allantoid to cylindrical, slightly curved, hyaline, thin- to slightly thick-walled, smooth, IKI–, CB–, (3.5–)3.7–4.2 × (0.8–)0.9–1.3(–1.4) μm, L = 3.94 μm, W = 1.09 μm, Q = 3.66 (n = 60/1).

Type of rot

Brown rot.

Cyanosporus subungulatus B.K. Cui & Shun Liu, sp. nov.

MycoBank No: 842321
Figs 8, 9

Diagnosis

Cyanosporus subungulatus is characterised by shell-shaped pileus with a pale mouse-grey to ash-grey pileal surface when fresh, dark-grey to mouse-grey when dry, allantoid to cylindrical and slightly curved basidiospores (4.5–5.2 × 1.1–1.4 μm).

Holotype

China. Yunnan Province, Yangbi County, Shimenguan Nature Reserve, on fallen trunk of Pinus sp., 6.IX.2019, Cui 18046 (BJFC 034905).

Etymology

Subungulatus (Lat.): referring to the species resembling Cyanosporus ungulatus in morphology.

Fruiting body

Basidiomata annual, pileate, soft corky, without odour or taste when fresh, becoming corky to fragile and light in weight upon drying. Pileus shell-shaped, projecting up to 1.7 cm, 2.8 cm wide and 1.2 cm thick at base. Pileal surface velutinate, pale mouse-grey to ash-grey when fresh, becoming smooth, rugose, dark-grey to mouse-grey when dry; margin obtuse. Pore surface white to cream when fresh, becoming cream to pinkish buff when dry; sterile margin narrow to almost lacking; pores round, 4–6 per mm; dissepiments thin, entire to lacerate. Context white to cream, soft corky, up to 5 mm thick. Tubes pale mouse-grey to ash-grey, fragile, up to 6 mm long.

Figure 8. 

Basidiomata of Cyanosporus subungulatus (Holotype, Cui 18046). Scale bar: 10 mm. The upper figure is the upper surface and the lower figure is the lower surface of the basidiomata.

Figure 9. 

Microscopic structures of Cyanosporus subungulatus (Holotype, Cui 18046) a basidiospores b basidia and basidioles c hyphae from trama d hyphae from context. Drawings by: Shun Liu.

Hyphal structure

Hyphal system monomitic; generative hyphae with clamp connections, IKI–, CB–; hyphae unchanged in KOH.

Context

Generative hyphae hyaline, slightly thick-walled with a wide lumen, rarely branched, loosely interwoven, 2.5–6.4 μm in diam.

Tubes

Generative hyphae hyaline, slightly thick-walled with a wide lumen, occasionally branched, interwoven, 2–4.2 μm in diam. Cystidia and cystidioles absent. Basidia clavate, bearing four sterigmata and a basal clamp connection, 13.6–17.8 × 3–5.5 μm; basidioles dominant, in shape similar to basidia, but smaller, 12.8–17.2 × 2.4–5.2 μm.

Spores

Basidiospores allantoid to cylindrical, slightly curved, hyaline, thin- to slightly thick-walled, smooth, IKI–, CB–, (4.3–)4.5–5.2 × 1.1–1.4 μm, L = 4.73 μm, W = 1.22 μm, Q = 3.48–3.66 (n = 60/2).

Type of rot

Brown rot.

Additional specimen (paratype) examined

China, Yunnan Province, Xichou County, Xiaoqiaogou Nature Reserve, on fallen angiosperm trunk, 14.I.2019, Zhao 10833 (SWFC 010833).

Cyanosporus tenuicontextus B.K. Cui & Shun Liu, sp. nov.

MycoBank No: 842323
Figs 10, 11

Diagnosis

Cyanosporus tenuicontextus is characterised by flabelliform pileus with a velutinate, cream to pinkish buff with a little blue tint pileal surface when fresh, becoming glabrous, light vinaceous grey to pale mouse-grey when dry, small and round pores (6–8 per mm), thin context (up to 0.8 mm) and allantoid basidiospores (3.8–4.3 × 0.8–1.2 μm).

Holotype

China. Yunnan Province, Lanping County, Tongdian Town, Luoguqing, on fallen trunk of Pinus sp., 19.IX.2017, Cui 16280 (BJFC 029579).

Etymology

Tenuicontextus (Lat.): referring to the species having thin context.

Fruiting body

Basidiomata annual, pileate, soft corky, without odour or taste when fresh, becoming corky to fragile and light in weight upon drying. Pileus flabelliform, projecting up to 1.3 cm, 3.2 cm wide and 0.5 cm thick at base. Pileal surface velutinate, cream to pinkish buff with a little blue tint when fresh, becoming glabrous, light vinaceous grey to pale mouse-grey when dry; margin acute. Pore surface white to cream when fresh, becoming pinkish buff to buff when dry; sterile margin narrow to almost lacking; pores round, 6–8 per mm; dissepiments thin, entire to lacerate. Context cream to buff, soft corky, up to 0.8 mm thick. Tubes pale mouse-grey to buff, fragile, up to 4.3 mm long.

Figure 10. 

Basidiomata of Cyanosporus tenuicontextus (Holotype, Cui 16280). Scale bar: 1 cm. The upper figure is the upper surface and the lower figure is the lower surface of the basidiomata.

Figure 11. 

Microscopic structures of Cyanosporus tenuicontextus (Holotype, Cui 16280) a basidiospores b basidia and basidioles. c cystidioles d hyphae from trama e hyphae from context. Drawings by: Shun Liu.

Hyphal structure

Hyphal system monomitic; generative hyphae with clamp connections, IKI–, CB–; hyphae unchanged in KOH.

Context

Generative hyphae hyaline, thin- to slightly thick-walled with a wide lumen, occasionally branched, loosely interwoven, 2.3–5.5 μm in diam.

Tubes

Generative hyphae hyaline, thin- to slightly thick-walled with a wide lumen, occasionally branched, interwoven, 2–4 μm in diam. Cystidia absent; cystidioles present, fusoid, thin-walled, 9.5–14.6 × 2.8–3.4 μm. Basidia clavate, bearing four sterigmata and a basal clamp connection, 11.7–16.8 × 3.4–4.3 μm; basidioles dominant, in shape similar to basidia, but smaller, 10.6–14.7 × 2.9–3.6 μm.

Spores

Basidiospores allantoid, slightly curved, hyaline, thin- to slightly thick-walled, smooth, IKI–, CB–, (3.7–)3.8–4.3 × 0.8–1.2 μm, L = 3.97 μm, W = 1.02 μm, Q = 3.78–4.26 (n = 60/2).

Type of rot

Brown rot.

Additional specimen (paratype) examined

China. Yunnan Province, Yuxi, Xinping County, Mopanshan National Forest Park, on angiosperm stump, 16.I.2017, Zhao 813 (SWFC 000813).

Discussion

In the current phylogenetic analyses based on the combined datasets of ITS+TEF and ITS+nLSU+mtSSU+nSSU+RPB1+RPB2+TEF sequences, species of Cyanosporus formed a highly supported lineage, distant from Postia and other brown-rot fungal genera (Figs 2, 3) and consistent with previous studies (Shen et al. 2019; Liu et al. 2021a). Based on morphological characters and phylogenetic analyses, 35 species are accepted in Cyanosporus around the world, including four new species from China, viz., C. flavus, C. rigidus, C. subungulatus and C. tenuicontextus. The main ecological habits of the species in Cyanosporus with an emphasis on distribution areas and host trees are provided in Table 2.

Table 2.

A list of species, specimens, and GenBank accession number of sequences used for phylogenetic analyses in this study.

Species Sample no. Locality GenBank accessions References
ITS nLSU mtSSU nSSU RPB1 RPB2 TEF
Amaropostia hainanensis Cui 13739 (holotype) China KX900909 KX900979 KX901053 KX901123 KX901171 KX901223 Shen et al. 2019
A. stiptica Cui 10043 China KX900906 KX900976 KX901046 KX901119 KX901167 KX901219 Shen et al. 2019
Amylocystis lapponica HHB-13400 United States KC585237 KC585059 Ortiz-Santana et al. 2013
A. lapponica OKM-4418 United States KC585238 KC585060 Ortiz-Santana et al. 2013
Antrodia serpens Dai 7465 Luxembourg KR605813 KR605752 KR606013 KR605913 KR610832 KR610742 Han et al. 2016
A. tanakae Cui 9743 China KR605814 KR605753 KR606014 KR605914 KR610833 KR610743 Han et al. 2016
Calcipostia guttulata Cui 10018 China KF727432 KJ684978 KX901065 KX901138 KX901181 KX901236 KX901276 Shen et al. 2019
C. guttulata Cui 10028 China KF727433 KJ684979 KX901066 KX901139 KX901182 KX901237 KX901277 Shen et al. 2019
Cyanosporus alni Petr Vampola 12.10.1995 (holotype) Slovakia MG137026 Miettinen et al. 2018
C. alni Cui 7185 China KX900879 KX900949 KX901017 KX901092 KX901155 KX901202 KX901254 Shen et al. 2019
C. alni Dai 14845 Poland KX900880 KX900950 KX901018 KX901093 KX901156 KX901203 KX901255 Shen et al. 2019
C. arbuti Viacheslav Spirin 8327 (holotype) United States MG137039 MG137132 Miettinen et al. 2018
C. auricomus Cui 13518 China KX900887 KX900957 KX901025 KX901100 KX901209 Shen et al. 2019
C. auricomus Cui 13519 China KX900888 KX900958 KX901026 KX901101 Shen et al. 2019
C. auricomus Tuomo Niemelä 8310 (holotype) Finland MG137040 Miettinen et al. 2018
C. bifarius Viacheslav Spirin 6402 (holotype) Russia MG137043 MG137133 Miettinen et al. 2018
C. bifarius Cui 17534 China OL423598* OL423608* OL437195* OL423620* OL444985* OL446999* OL444994* Present study
C. bifarius Cui 16277 China OL423599* OL423609* OL437196* OL423621* OL444986* OL447000* OL444995* Present study
C. bubalinus Cui 16976 China MW182172 MW182225 MW182208 MW182189 MW191547 MW191563 MW191530 Liu et al. 2021a
C. bubalinus Cui 16985 (holotype) China MW182173 MW182226 MW182209 MW182190 MW191548 MW191564 MW191531 Liu et al. 2021a
C. caesiosimulans Viacheslav Spirin 4199 Russia MG137061 MG137140 Miettinen et al. 2018
C. caesiosimulans Otto Miettinen 16976 (holotype) United States MG137054 MG137137 Miettinen et al. 2018
C. caesius Gerhard Schuster 51 (neotype) Germany MG137045 Miettinen et al. 2018
C. caesius Otto Miettinen 14156 Finland MG137048 MG137134 Miettinen et al. 2018
C. caesius Cui 18630 France OL423600* OL423610* OL437197* OL423622* OL444996* Present study
C. caesius aff GB K 32713 United Kingdom AY599576 Miettinen et al. 2018
C. caesius aff GB K 32425 United Kingdom AY599575 Miettinen et al. 2018
C. coeruleivirens Otto Miettinen 12214 Indonesia MG137063 Miettinen et al. 2018
C. coeruleivirens Dai 19220 China MW182174 MW182227 MW182210 MW182191 MW191549 MW191532 Liu et al. 2021a
C. comatus Otto Miettinen 14755,1 (holotype) United States MG137066 Miettinen et al. 2018
C. cyanescens Otto Miettinen 13602 (holotype) Finland MG137067 MG137142 Miettinen et al. 2018
C. cyanescens Otto Miettinen 15919,2 Spain MG137071 MG137144 Miettinen et al. 2018
C. flavus Cui 18547 China MW448564 * MW448561 * MW448557 * MW452596 * MW452599 * MW452601 Present study
C. flavus Cui 18562 (holotype) China MW448565 * MW448562 * MW448558 * MW452597 * MW452600 * MW452602 Present study
C. fusiformis Cui 10775 China KX900868 KX900938 KX901006 KX901081 KX901191 KX901245 Shen et al. 2019
C. fusiformis Dai 15036 (holotype) China KX900867 KX900937 KX901005 KX901080 KX901190 KX901244 Shen et al. 2019
C. glaucus Viacheslav Spirin 5317 Russia MG137078 Miettinen et al. 2018
C. glaucus Viacheslav Spirin 6580 (holotype) Russia MG137081 MG137145 Miettinen et al. 2018
C. gossypinus Bernard Rivoire 6658 France MG137146 Miettinen et al. 2018
C. hirsutus Cui 17083 (holotype) China MW182179 MW182233 MW182214 MW182197 MW191554 MW191568 MW191538 Liu et al. 2021a
C. hirsutus Cui 17343 China OL423601* OL423611* OL437198* OL423623* OL444987* OL447001* OL444997* Present study
C. hirsutus Cui 17342 China OL423602* OL423612* OL437199* OL423624* OL444988* OL447002* OL444998* Present study
C. livens Viacheslav Spirin 8728 United States MG137090 MG137150 Miettinen et al. 2018
C. livens Otto Miettinen 17177 (holotype) United States MG137082 MG137147 Miettinen et al. 2018
C. luteocaesia Bernard Rivoire 2605 France MG137091 Miettinen et al. 2018
C. magnus Dai 21105 China OL423603* OL423613* OL437200* OL423625* OL444989* OL447003* OL444999* Present study
C. magnus Cui 16983 China MW182180 MW182234 MW182215 MW182198 MW191555 MW191569 MW191539 Liu et al. 2021a
C. magnus Otto Miettinen 10634 (holotype) China KC595944 KC595944 MG137151 Miettinen et al. 2018
C. mediterraneocaesius LY BR 4274 France KX900886 KX901024 KX901099 Shen et al. 2019
C. microporus Cui 11014 (holotype) China KX900878 KX900948 KX901016 KX901091 KX901201 Shen et al. 2019
C. microporus Dai 11717 China KX900877 KX900947 KX901015 KX901090 KX901200 Shen et al. 2019
C. nothofagicola Cui 16697 (holotype) Australia MW182181 MW182235 MW182216 MW182199 MW191556 MW191570 MW191540 Liu et al. 2021a
C. nothofagicola Dai 18765 Australia MW182182 MW182236 MW182217 MW182200 MW191557 MW191541 Liu et al. 2021a
C. piceicola Cui 10626 (holotype) China KX900862 KX900932 KX901001 KX901075 KX901185 Shen et al. 2019
C. piceicola Cui 12158 China KX900866 KX900936 KX901004 KX901079 KX901153 KX901189 KX901243 Shen et al. 2019
C. populi Otto Miettinen 17043 (holotype) United States MG137092 MG137153 Miettinen et al. 2018
C. populi Cui 17087a China MW182183 MW182237 MW182218 MW182201 MW191558 MW191571 MW191542 Liu et al. 2021a
C. populi Dai 18934 China OL423604* OL423614* OL437201* OL423626* OL444990* OL447004* OL445000* Present study
C. populi Cui 17557 China OL423605* OL423615* OL437202* OL423627* OL444991* OL447005* OL445001* Present study
C. rigidus Cui 17032 (holotype) China OL423606 * OL423617 * OL437204 * OL423629 * OL444993 * OL445003 * Present study
C. simulans Otto Miettinen 20422 Finland MG137110 MG137160 Miettinen et al. 2018
C. simulans Tuomo Niemelä 8846 (holotype) Finland MG137103 Miettinen et al. 2018
C. subcaesius Josef Vlasák 0110/24 Czech Republic MG137117 MG137164 Miettinen et al. 2018
C. subcaesius Alix David 652 (isotype) France MG137116 Miettinen et al. 2018
C. subhirsutus Cui 11330 China KX900873 KX900943 KX901011 KX901086 KX901196 KX901250 Shen et al. 2019
C. subhirsutus Dai 14892 (holotype) China KX900871 KX900941 KX901009 KX901084 KX901194 KX901248 Shen et al. 2019
C. submicroporus Cui 16306 China MW182184 MW182239 MW182220 MW182203 MW191560 MW191573 MW191544 Liu et al. 2021a
C. submicroporus Cui 18156 (holotype) China MW182186 MW182241 MW182222 MW182205 MW191574 Liu et al. 2021a
C. subungulatus Cui 18046 (holotype) China MW448566 * MW448563 * MW448560 * MW448559 * MW452598 * MW452603 Present study
C. subungulatus Zhao 10833 China MW742586 * OL423616 * OL437203 * OL423628 * OL444992 * OL445002 * Present study
C. subviridis Viacheslav Spirin 8774a United States MG137120 MG137166 Miettinen et al. 2018
C. subviridis Reijo Penttilä 14376 Finland MG137165 Miettinen et al. 2018
C. tenuicontextus Cui 16280 (holotype) China OL423607 * OL423618 * OL437205 * OL423630 * OL445004 * Present study
C. tenuicontextus Zhao 813 China MG231802 * OL423619 * OL437206 * OL423631 * OL445005 * Present study
C. tenuis Cui 10788 (holotype) China KX900885 KX900955 KX901023 KX901098 KX901161 KX901208 Shen et al. 2019
C. tenuis Dai 12974 China KX900884 KX900954 KX901022 KX901097 KX901160 KX901207 KX901258 Shen et al. 2019
C. tricolor Cui 12233 (holotype) China KX900876 KX900946 KX901014 KX901089 KX901199 KX901253 Shen et al. 2019
C. tricolor Cui 10790 China KX900875 KX900945 KX901013 KX901088 KX901198 KX901252 Shen et al. 2019
C. ungulatus Cui 10778 China KX900870 KX900940 KX901008 KX901083 KX901193 KX901247 Shen et al. 2019
C. ungulatus Dai 12897 (holotype) China KX900869 KX900939 KX901007 KX901082 KX901154 KX901192 KX901246 Shen et al. 2019
C. yanae Heikki Kotiranta 27606 Russia MG137122 MG137168 Miettinen et al. 2018
C. yanae Heikki Kotiranta 27454 (holotype) Russia MG137121 MG137167 Miettinen et al. 2018
Cystidiopostia hibernica Cui 2658 China KX900905 KX900975 KX901045 KX901118 KX901218 Shen et al. 2019
C. inocybe LY BR 3703 France KX900903 KX900973 KX901044 KX901116 KX901267 Shen et al. 2019
C. pileata Cui 10034 China KX900908 KX900956 KX901050 KX901122 KX901170 KX901222 KX901269 Shen et al. 2019
Fuscopostia duplicate Dai 13411 (holotype) China KF699125 KJ684976 KR606027 KR605928 KX901174 KR610845 KR610756 Han et al. 2016
F. fragilis JV 0610-8 Czech JF950573 Vampola et al. 2014
F. lateritia Dai 2652 China KX900913 KX900983 Shen et al. 2019
F. leucomallella Cui 9599 China KF699123 KJ684983 KX901056 KX901129 KX901176 KX901228 KX901272 Shen et al. 2019
Jahnoporus brachiatus X 3232 Russia KU165781 Spirin et al. 2015
J. hirtus Spinosa 10 X 2014 United States KU165784 KY949044 Spirin et al. 2015
J. oreinus X 3241 Russia KU165785 Spirin et al. 2015
Oligoporus rennyi TN-6645 Finland KC595929 KC595929 Ortiz-Santana et al. 2013
O. sericeomollis Cui 9870 China KX900920 KX900990 KX901068 KX901141 KX901184 Shen et al. 2019
Osteina obducta Cui 10074 China KX900924 KX900994 KX901071 KX901144 KX901240 Shen et al. 2019
O. undosa Dai 7105 China KX900921 KX900991 KX901069 KX901142 KX901238 Shen et al. 2019
Postia amurensis Dai 903 (holotype) China KX900901 KX900971 KX901042 Shen et al. 2019
P. hirsuta Cui 11237 (holotype) China KJ684970 KJ684984 KX901038 KX901113 KX901266 Shen et al. 2019
P. lactea Cui 12141 China KX900892 KX900962 KX901029 KX901104 KX901163 KX901211 KX901260 Shen et al. 2019
P. lowei Cui 9585 China KX900898 KX900968 KX901035 KX901110 Shen et al. 2019
P. ochraceoalba Cui 10802 (holotype) China KM107903 KM107908 KX901041 KX901115 KX901216 Shen et al. 2015
P. sublowei Cui 9597 (holotype) China KX900900 KX900970 KX901037 KX901112 KX901265 Shen et al. 2019
P. tephroleuca Dai 12610 Finland KX900897 KX900967 KX901034 KX901109 KX901166 KX901214 KX901263 Shen et al. 2019
Spongious gloeoporus Cui 10401 China KX900915 KX900985 KX901060 KX901133 KX901232
S. floriformis Cui 10292 China KM107899 KM107904 KX901058 KX901131 KX901178 KX901230 KX901274
S. floriformis Dai 13887 China KX900914 KX900984 KX901057 KX901130 KX901177 KX901229 KX901273

In the phylogenetic trees, Cyanosporus flavus grouped together with C. fusiformis, C. subungulatus and C. ungulatus (Figs 2, 3). Cyanosporus fusiformis differs from C. flavus by having white to cream pileal surface when fresh, clay-buff pore surface when dry and larger pores (4–5 per mm) and by growing on angiosperm woods (Shen et al. 2019); C. subungulatus differs from C. flavus in its glabrous pileal surface, cream to pinkish buff pore surface when dry and wider basidiospores (4.5–5.2 × 1.1–1.4 μm); C. ungulatus differs from C. flavus by having ungulate basidiomata, sulcate pileal surface with olivaceous buff, pinkish buff, cream to ash-grey and white zones when fresh (Shen et al. 2019). Cyanosporus hirsutus and C. subhirsutus have pileate basidiomata with hirsute, blue tint to the pileal surface and slightly thick-walled basidiospores like C. flavus, but C. hirsutus differs by having wider basidiospores (4–4.7 × 1.2–1.5 μm; Liu et al. 2021a), while C. subhirsutus has larger pores (2–3 per mm; Shen et al. 2019). Besides, C. hirsutus and C. subhirsutus are distant from C. flavus in the phylogenetic analyses (Figs 2, 3). Cyanosporus subungulatus and C. ungulatus share similar pores and basidiospores; however, C. ungulatus differs by having ungulate basidiomata, glabrous and sulcate pileal surface, narrower context hyphae and tramal hyphae (Shen et al. 2019).

Phylogenetically, Cyanosporus rigidus form a separate lineage different from other species in the genus. Morphologically, C. submicroporus share similar pores and basidiospores with C. rigidus, but C. submicroporus differs by having cream to pinkish buff pileal surface and white to smoke grey pore surface when fresh, buff to buff-yellow pileal surface and buff to olivaceous buff pore surface when dry. Cyanosporus auricomus and C. luteocaesius resemble C. rigidus in morphology by producing yellow-colored basidiomata, but C. auricomus differs from C. rigidus by having a hirsute pileal surface and larger basidiospores (4.4–5.6 × 1.5–1.8 μm; Miettinen et al. 2018); C. luteocaesius differs from C. rigidus by having larger pores (3–5 per mm) and basidiospores (4.3–6.1 × 1.5–1.9 μm; Miettinen et al. 2018).

Phylogenetically, C. tenuicontextus is closely related to C. caesiosimulans, C. cyanescens, C. populi, C. subviridis and C. yanae (Figs 2, 3). Morphologically, they share similar pores; but C. caesiosimulans differs by having larger basidiospores (4.2–5.5 × 1.1–1.4 μm), and a wide distribution area (Europe and North America; Miettinen et al. 2018); C. cyanescens differs in having light bluish-greyish tint in older and dry specimens and larger basidiospores (4.7–6.1 × 1.1–1.6 μm; Miettinen et al. 2018); C. populi differs in its larger basidiospores (4.2–5.6 × 1–1.3 μm), and a wide distribution area (East Asia, Europe and North America; Miettinen et al. 2018; Liu et al. 2021a); C. subviridis differs in its conchate basidiomata, distributed in Europe and North America and grows only on gymnosperms (Abies sp., Picea sp. and Pinus sp.; Miettinen et al. 2018); C. yanae differs by having narrower generative hyphae (3–4 μm in context, 2.2–2.9 μm in tubes), larger basidiospores (4.3–5.8 × 1.2–1.6 μm), distributed in Europe and grows only on gymnosperm (Larix sp., Pinus sp.; Miettinen et al. 2018). Cyanosporus bifarius is also distributed in Lanping County, Yunnan Province of China, they share similar pores and basidiospores, but C. bifarius grows only on gymnosperm trees (Picea sp., Pinus sp., Larix sp.; Miettinen et al. 2018), and C. bifarius is distant from C. tenuicontextus in the phylogenetic analyses (Figs 2, 3).

The natural distribution of plant-associated fungi across broad geographic ranges is determined by a combination of the distributions of suitable hosts and environmental conditions (Lodge 1997; Brandle and Brandl 2006; Gilbert et al. 2007, 2008). Species in Cyanosporus have a wide distribution range (Asia, Europe, North America, South America and Oceania; Table 2) and variable host type (angiosperms and gymnosperms). As for distribution ranges, 23 species of Cyanosporus are distributed in Asia, 16 species in Europe, seven species in North America, one species in South America and one species in Oceania. As for host trees, nine species of Cyanosporus grow only on angiosperm trees, 15 species only on gymnosperm trees, and eleven species both on angiosperm and gymnosperm trees (Table 1). In some cases, some Cyanosporus species have host specificity, at least regionally, such as in Europe, C. auricomus only growth on Pinus sylvestris, C. cyanescens only growth on Picea abies, C. populi prefers Populus tremula, and C. luteocaesia have been recorded only from Pinus sp. (Miettinen et al. 2018).

In the current study, 77 samples of Cyanosporus throughout China and 11 samples outside of China have been morphologically examined in detail. The specimens collected from China representing 21 species were sequenced here and referred to in our phylogeny, viz., C. alni, C. auricomus, C. bifarius, C. bubalinus, C. coeruleivirens, C. comatus, C. flavus, C. fusiformis, C. hirsutus, C. magnus, C. microporus, C. piceicola, C. populi, C. rigidus, C. subhirsutus, C. submicroporus, C. subungulatus, C. tenuicontextus, C. tenuis, C. tricolor and C. ungulatus. Another two species reported in a previous study, viz., C. glauca (=Postia glauca Spirin & Miettinen) and C. simulans (=Postia simulans (P. Karst.) Spirin & Rivoire; Miettinen et al. 2018) were also found from China. Among these Cyanosporus species, 15 are endemic to China so far, viz., C. bubalinus, C. flavus, C. fusiformis, C. hirsutus, C. microporus, C. piceicola, C. rigidus, C. subhirsutus, C. submicroporus, C. subungulatus, C. tenuicontextus, C. tenuis, C. tricolor and C. ungulatus. The Cyanosporus species formed a distribution center in Southwest China. This may be due to the complex and diverse ecological environment and diverse host trees in this region, which provide a rich substrate for the growth of Cyanosporus species. The geographical locations of the Cyanosporus species distributed in China are indicated on the map (Fig. 1).

In summary, we performed a comprehensive study on the species diversity and phylogeny of Cyanosporus with an emphasis on Chinese collections. So far, 35 species are accepted in the Cyanosporus around the world, including 23 species from China. Currently, Cyanosporus is characterized by an annual growth habit, resupinate to effused-reflexed or pileate, soft corky, corky, fragile to hard corky basidiomata, velutinate to hirsute or glabrous pileal surface with blue-tinted, white to cream or yellow-colored, white to cream pore surface with round to angular pores, a monomitic hyphal system with clamped generative hyphae, and hyaline, thin- to slightly thick-walled, smooth, narrow, allantoid to cylindrical basidiospores that are usually weakly cyanophilous; it grows on different angiosperm and gymnosperm trees, causes a brown rot of wood and has a distribution in Asia, Europe, North America, Argentina in South America and Australia in Oceania (McGinty 1909; Shen et al. 2019; Liu et al. 2021a).

Acknowledgements

We express our gratitude to the curators of herbaria of IFP and SWFC for their loan of specimens. Ms. Yi-Fei Sun (China), Xing Ji (China) and Yan Wang (China) are grateful for help during field collections and molecular studies. Drs. Jun-Zhi Qiu (China), Shi-Liang Liu (China) and Long-Fei Fan (China) are thanked for their companionship during field collections. The research is supported by the National Natural Science Foundation of China (Nos. U2003211, 31750001), the Scientific and Technological Tackling Plan for the Key Fields of Xinjiang Production and Construction Corps (No. 2021AB004), and Beijing Forestry University Outstanding Young Talent Cultivation Project (No. 2019JQ03016).

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