Neoboletus infuscatus, a new tropical bolete from Hainan, southern China

Abstract

Neoboletus infuscatus (Boletaceae, Boletales) is described as a new species from Yinggeling of Hainan Tropical Rainforest National Park, southern China. It is morphologically characterized by a large basidioma with a nearly glabrous, brownish yellow, yellowish brown to pale brown pileus, pores orangish red when young, yellowish brown to brown when old, context and hymenophore staining blue when injured, a yellow stipe with red punctuations, surfaces of the pileus and the stipe usually covered with a thin layer of white pruina when young. Phylogenetic analyses of DNA sequences from part of the 28S gene, the nuclear rDNA internal transcribed spacer (ITS) region, and part of the translation elongation factor 1-α gene (TEF1) also confirm that N. infuscatus forms an independent lineage within Neoboletus. Detailed morphological description, color photos of fresh basidiomata and line-drawings of microstructures are provided.

Members of Boletaceae are diverse worldwide and attracted much attentions due to their ectomycorrhizal, edibility, toxicity and pharmaceutical potentialities (Roman, Claveria, & Miguel, 2005; Sitta & Floriani, 2008; Dentinger et al., 2010; Feng et al., 2012; Wu et al., 2013; Chen, Yang, Tolgor, & Li, 2016). With the development of molecular techniques, several new species were discovered. In addition, some species were reassessed and new genera were established to accommodate certain taxa in Boletaceae (Li, Feng, & Yang, 2011; Arora & Frank, 2014; Zeng, Wu, Li, Liang, & Yang, 2014; Gelardi, Simonini, Ercole, Davoli, & Vizzini, 2015; Farid et al., 2018). Neoboletus Gelardi, Simonini & Vizzini was newly segregated from Boletus L. and typified by N. luridiformis (Rostk.) Gelardi, Simonini & Vizzini (Vizzini, 2014). This treatment was phylogenetically supported (Binder & Hibbett, 2006; Nuhn, Binder, Taylor, Halling, & Hibbett, 2013; Arora & Frank, 2014; Urban & Klofac, 2015) and accepted by more and more researchers (Urban & Klofac, 2015; Sarwar, Jabeen, Khalid, & Dentinger, 2016; Gelardi, 2017; Chai et al., 2019; Gelardi et al., 2019; Vadthanarat, Lumyong, & Raspé, 2019; Kuo & Ortiz-Santana, 2020). The genus is characterized by stipitate-pileate or sequestrate basidiomata; when basidiomata stipitate-pileate, pores brown, dark brown to reddish brown when young, becoming yellow when old, tubes always yellow, hymenophore and context staining blue, and stipe usually covered with punctuations (Vizzini, 2014; Wu et al., 2016b; Chai et al., 2019). Yinggeling of Hainan Tropical Rainforest National Park, southern China is considered a hotspot of biodiversity (Jiang et al., 2013). In the past decade, thirteen new species of macrofungi including boletes were described in the region (Liang, An, Jiang, Su, & Zeng, 2016; Liang, Chai, Jiang, Ye, & Zeng, 2017a; Liang, Su, Jiang, & Zeng, 2017b; An, Liang, Jiang, Su, & Zeng, 2017; Zeng, Liang, Tang, Li, & Yang, 2017; Zeng et al., 2018; Chai, Liang, Jiang, Fu, & Zeng, 2018; Chai et al., 2019; Xue et al., 2019; Wang et al., 2020; Xie et al., 2020). With further field investigations, more new species are expected to be discovered. Recently, we encountered some specimens in Yinggeling, which of the genus proved to be a new species of genus Neoboletus by morphological and molecular phylogenetic analyses. Therefore, a detailed description of the new species was presented.

Fresh specimens were photographed in the field, a collection number was given for each specimen, and a detailed record of morphological characters of fresh fruit body was also made, then the specimens were dried with air flow dryer and deposited in the Fungal Herbarium of Hainan Medical University (FHMU), Haikou City, Hainan Province of China. Color codes are from Kornerup and Wanscher (1981). Sections of the pileipellis on the pileus were cut perpendicularly and halfway between the center and margin of the pileus. Sections of the stipitipellis on the stipe were taken from the middle part along the longitudinal axis of the stipe. KOH (5%) was used as a mounting medium for microscopic studies. All the microscopic structures were observed and measured with an optical light microscope (CX23, Olympus, Tokyo, Japan), then drawn freehand from rehydrated material. The number of measured basidiospores is given as n/m/p, where n represents the total number of basidiospores measured from m basidiomata of p collections. Dimensions of basidiospores are given as (a)b–c(d), where the range b–c represents a minimum of 90% of the measured values (5th to 95th percentile), and extreme values (a and d), whenever present (a < 5th percentile, d > 95th percentile), are in parentheses. Q refers to the length/width ratio of basidiospores; Qm refers to the average Q of basidiospores and is given with standard deviation.

Total genomic DNA was obtained with Plant Genomic DNA Kit (TIANGEN Company, Beijing, China) from materials dried with silica gel according to the manufacturer’s instructions. Primer pairs used for amplifying the nuclear ribosomal large subunit RNA (28S) were LROR/LR5 (Vilgalys & Hester, 1990; James et al., 2006), ITS5/ITS4 (White, Bruns, Lee, & Taylor, 1990) for the nuclear rDNA region encompassing the internal transcribed spacers 1 and 2, along with the 5.8S rDNA (ITS), and EF1-α-F/EF1-α-R (Mikheyev, Mueller, & Abbot, 2006) for the translation elongation factor 1-α gene (TEF1). PCR was performed in a total volume of 25 μL containing 13 μL GoTaq® Green Master Mix (Promega, Madison, USA), 2 μL per primer (10 mM), 2 μL DNA template and 8 μL nuclease-free water. PCR reactions were performed with 4 min initial denaturation at 95 °C, followed by 34 cycles of denaturation at 94 °C for 30 s, annealing at 50 °C (28S and ITS) or 53 °C (TEF1) for 30 s and extension at 72 °C for 120 s, a final extension at 72 °C for 7 min. PCR products were checked in 1% (w/v) agarose gels, and positive reactions with a bright single band were purified and directly sequenced using an ABI 3730xl DNA Analyzer (Guangzhou Branch of BGI, Guangzhou, China) with the same primers used for PCR amplifications. Forward or reverse sequences were compiled with BioEdit (Hall, 1999). Assembled sequences were deposited in GenBank (Table 1).

Table 1 Taxa, vouchers, locations, and GenBankaccession numbers of DNA sequences used in this study.

Taxon	Voucher	Locality	GenBank accession no.
			28S	ITS	TEF1
Neoboletus brunneissimus	HKAS50538	Yunnan, SW China	KM605138	—	KM605150	Wu et al. 2016b
N. brunneissimus	HKAS52660	Yunnan, SW China	KF112314	—	KF112143	Wu et al. 2014
N. brunneissimus	HKAS57451	Yunnan, SW China	KM605137	—	KM605149	Wu et al. 2016b
N. brunneissimus	OR0249	China	—	—	MG212595	Vadthanarat et al. 2018
Neoboletus erythropus	VDKO0690	Belgium	—	—	KT824048	Raspé et al. 2016
Neoboletus ferrugineus	HKAS77617	Guangdong, southern China	KT990595	—	KT990788	Wu et al. 2016a
N. ferrugineus	HKAS77718	Guangdong, southern China	KT990596	—	KT990789	Wu et al. 2016a
Neoboletus flavidus	HKAS58724	Yunnan, SW China	KU974140	—	KU974137	Wu et al. 2016a
N. flavidus	HKAS59443	Yunnan, SW China	KF974139	—	KU974136	Wu et al. 2016a
Neoboletus hainanensis	HKAS59469	Yunnan, SW China	KF112359	—	KF112175	Wu et al. 2014
N. hainanensis	HKAS63515	Yunnan, SW China	KT990614	—	KT990808	Wu et al. 2016a
N. hainanensis	HKAS74880	Yunnan, SW China	KT990597	—	KT990790	Wu et al. 2016a
N. hainanensis	HKAS90209	Hainan, southern China	KT990615	—	KT990809	Wu et al. 2016a
N. hainanensis	N.K. Zeng2128 (FHMU1392)	Yunnan, SW China	MH879690	—	MH879719	Chai et al. 2019
Neoboletus infuscatus	N.K. Zeng3352 (FHMU3370)	Hainan, southern China	MW293785	MW293793	MW307255	This study
N. infuscatus	N.K. Zeng4030 (FHMU3371	Hainan, southern China	MW293786	—	MW307256	This study
N. infuscatus	N.K. Zeng4031 (FHMU3372)	Hainan, southern China	MW293787	—	MW307257	This study
Neoboletus junquilleus	AF2922	France	—	—	MG212596	Vadthanarat et al. 2018
N. luridiformis	AT2001087	Berkshire, England	JQ326995	—	JQ327023	Halling et al. 2012
Neoboletus magnificus	HKAS54096	Yunnan, SW China	KF112324	—	KF112149	Wu et al. 2014
N. magnificus	HKAS74939	Yunnan, SW China	KF112320	—	KF112148	Wu et al. 2014
N. magnificus	N.K. Zeng4038 (FHMU3373)	Hainan, southern China	MW293788	—	MW307258	This study
Neoboletus multipunctatus	HKAS76851	Hainan, southern China	KF112321	—	KF112144	Wu et al. 2014
N. multipunctatus	N.K. Zeng2498 (FHMU1620)	Hainan, southern China	MH879693	MH885354	MH879722	Chai et al. 2019
N. multipunctatus	OR0128	Thailand	—	—	MH614734	Vadthanarat et al. 2019
Neoboletus obscureumbrinus	CMU58-ST-0237	Thailand	KX017292	KX017301	—	GenBank
N. obscureumbrinus	HKAS63498	Yunnan, SW China	KT990598	—	KT990791	Wu et al. 2016a
N. obscureumbrinus	HKAS77774	Yunnan, SW China	—	—	KT990792	Wu et al. 2016a
N. obscureumbrinus	HKAS89014	Yunnan, SW China	KT990599	—	KT990793	Wu et al. 2016a
N. obscureumbrinus	HKAS89027	Yunnan, SW China	KT990600	—	KT990794	Wu et al. 2016a
N. obscureumbrinus	N.K. Zeng3091 (FHMU2052)	Hainan, southern China	MH879694	MH885355	MH879723	Chai et al. 2019
N. obscureumbrinus	N.K. Zeng3094 (FHMU2055)	Hainan, southern China	MH879695	MH885356	MH879724	Chai et al. 2019
N. obscureumbrinus	N.K. Zeng3098 (FHMU2059)	Hainan, southern China	MH879696	MH885357	MH879725	Chai et al. 2019
N. obscureumbrinus	OR0553	Thailand	—	—	MK372282	Vadthanarat, Lumyong, & Raspé, 2019
Neoboletus rubriporus	HKAS57512	Yunnan, SW China	KF112327	—	KF112151	Wu et al. 2014
N. rubriporus	HKAS83026	Yunnan, SW China	KT990601	—	KT990795	Wu et al. 2016a
N. rubriporus	HKAS89174	Yunnan, SW China	KT990602	—	KT990796	Wu et al. 2016a
N. rubriporus	HKAS89181	Yunnan, SW China	KT990603	—	KT990797	Wu et al. 2016a
N. rubriporus	HKAS90210	Yunnan, SW China	KT990604	—	KT990798	Wu et al. 2016a
N. rubriporus	MHKMU-L.P. Tang1958	Yunnan, SW China	—	MH885358	MH879726	Chai et al. 2019
Neoboletus sanguineoides	HKAS55440	Yunnan, SW China	KF112315	—	KF112145	Wu et al. 2014
N. sanguineoides	HKAS57766	Yunnan, SW China	KT990605	—	KT990799	Wu et al. 2016a
N. sanguineoides	HKAS63530	Sichuan, SW China	KT990607	—	KT990801	Wu et al. 2016a
N. sanguineoides	HKAS74733	Yunnan, SW China	KT990606	—	KT990800	Wu et al. 2016a
N. sanguineus	HKAS68587	Yunnan, SW China	KF112329	—	KF112150	Wu et al. 2016a
N. sanguineus	HKAS80823	Yunnan, SW China	KT990608	—	KT990802	Wu et al. 2016a
N. sanguineus	HKAS80849	Yunnan, SW China	KT990609	—	KT990803	Wu et al. 2016a
N. sanguineus	HKAS90211	Xizang, SW China	KT990610	—	KT990804	Wu et al. 2016a
Neoboletus sp.	HKAS50351	Yunnan, SW China	KF112318	—	—	Wu et al. 2014
Neoboletus sp.	HKAS76660	Henan, central China	KF112328	—	KF112180	Wu et al. 2014
Neoboletus thibetanus	HKAS57093	Xizang, SW China	KF112326	—	—	Wu et al. 2014
Neoboletus tomentulosus	HKAS53369	Fujian, SE China	KF112323	—	KF112154	Wu et al. 2014
N. tomentulosus	HKAS77656	Guangdong, southern China	KT990611	—	KT990806	Wu et al. 2016a
N. tomentulosus	N.K. Zeng1285 (FHMU841)	Fujian, SE China	MH879691	MH885352	MH879720	Chai et al. 2019
N. tomentulosus	N.K. Zeng1286 (FHMU842)	Fujian, SE China	MH879692	MH885353	MH879721	Chai et al. 2019
Neoboletus venenatus	HKAS57489	Yunnan, SW China	KF112325	—	KF112158	Wu et al. 2014
N. venenatus	HKAS63535	Sichuan, SW China	KT990613	—	KT990807	Wu et al. 2016a
Sutorius subrufus	N.K. Zeng3043 (FHMU2004)	Hainan, southern China	MH879698	MH885360	MH879728	Chai et al. 2019
S. subrufus	N.K. Zeng3045 (FHMU2006)	Hainan, southern China	MH879699	MH885361	MH879729	Chai et al. 2019

Nine sequences (four of 28S, one of ITS, four of TEF1) from four collections were newly generated and deposited in GenBank (Table 1). For the concatenated data set, the 28S, ITS, and TEF1 sequences were aligned with selected sequences from GenBank and previous studies (Table 1). Sutorius subrufus N.K. Zeng, H. Chai & S. Jiang was chosen as outgroup based on the phylogeny in Chai et al. (2019). Single-gene phylogenetic trees based on the 28S, ITS, and TEF1 fragments, respectively, were analyzed to test for phylogenetic conflict. The topologies of the phylogenetic trees based on a single gene were almost identical, indicating that the phylogenetic signals present in the different gene fragments were not in conflict. Then, the sequences of the different genes were aligned using MUSCLE (Edgar, 2004), and alignments were purged from unreliably aligned positions and gaps using Gblocks (Castresana, 2000). The sequences of the different genes were concatenated using Phyutility v2.2 for further analyses (Smith & Dunn, 2008).

The combined nuclear data set (28S + ITS + TEF1) was analyzed by using Maximum Likelihood (ML) and Bayesian Inference (BI). Maximum likelihood tree generation and bootstrap analyses were performed with the program RAxML 7.2.6 (Stamatakis, 2006) running 1,000 replicates combined with a ML search. A bayesian analysis with MrBayes 3.1 (Huelsenbeck & Ronquist, 2005) implementing the Markov Chain Monte Carlo (MCMC) technique and parameters predetermined with MrModeltest 2.3 (Nylander, 2004) was performed. The model of evolution used in the Bayesian analysis was determined with MrModeltest 2.3 (Nylander, 2004). For the three-gene combined data set of Neoboletus, the best-fit likelihood models of 28S, ITS and TEF1 were GTR+I+G, HKY+G and SYM +G, respectively. Bayesian analysis was repeated for 5.4 million generations and sampled every 100 generations; trees sampled from the first 25% of the generations were discarded as burn-in; the average standard deviation of split frequencies was restricted to be below 0.01, and Bayesian posterior probabilities (PP) were then calculated for a majority consensus tree of the retained Bayesian trees.

The three-locus data set (28S + ITS + TEF1) consisted of 59 taxa and 2154 nucleotide sites. The aligned data set was submitted to TreeBASE (S27329). The topologies of phylogenetic trees based on the combined data set generated from ML and BI analyses were almost identical, while statistical supports showed slight differences. The phylogram with branch lengths generated from RAxML, including the support values, is shown in Fig. 1.

The molecular phylogenetic analyses show that the collections numbered FHMU3370, FHMU3371, FHMU3372, respectively, grouped together with a high statistical support (BS=100, PP =1), forming an independent lineage within Neoboletus (Fig. 1).

Fig. 1 - Phylogenetic placement of Neoboletus infuscatus inferred from a combined (rDNA 28S, ITS, and TEF1) data set using RAxML. BS ≥ 50% and PP ≥ 0.95 are indicated above or below the branches as RAxML BS/PP.

Taxonomy

Neoboletus infuscatus N.K. Zeng, S. Jiang & Zhi Q. Liang, sp. nov. Figs 2, 3.

MycoBank no.: MB 838173.   

Fig. 2 - Basidiomata of Neoboletus infuscatus. A–C: FHMU3370. D: FHMU3371; E, F: FHMU3372 (holotype). Photos by N. K. Zeng.

Fig. 3 - Microscopic features of Neoboletus infuscatus (FHMU3372, holotype). A: Basidia. B: Basidiospores. C: Cheilocystidia. D: Pleurocystidia. E: Pileipellis. F: Stipitipellis. Bars: 10 μm. Drawings by S. Jiang.

Diagnosis: Characterized by a large basidioma with a nearly glabrous, brownish yellow, yellowish brown to pale brown pileus, pores orangish red when young, yellowish brown to brown when old, context and hymenophore staining blue when injured, a yellow stipe with red punctuations, surfaces of pileus and stipe usually covered with a thin layer of white pruina when young, and smaller basidiospores measuring 8.5–10.5 × 3.5–4.5 μm.

Type: CHINA, Hainan Province, Ledong County, Yinggeling Branch of Hainan Tropical Rainforest National Park, Nanfaling, elev. 560 m, gregarious on the ground in forests dominated by fagaceous trees, 24 Apr 2019, N.K. Zeng4031 (holotype, FHMU3372).

Gene sequences ex-holotype: MW293787 (28S), MW307257 (TEF1).

Etymology: Latin “infuscatus”, referring to the species having a pale brown pileus.

Basidiomata medium-sized to large. Pileus 6–16 cm diam, subhemispherical when young, then convex to applanate; margin decurved, sometimes slightly uplifted when old; surface dry, nearly glabrous, brownish yellow (1B3), yellowish brown (3B4) to pale brown (3B7), sometimes covered with a thin layer of white pruina when young; context 1.8–2 cm thick in the center of the pileus, yellowish white (1A2), changing blue (21A3) quickly when injured. Hymenophore poroid, slightly depressed around the stipe; pores stuffed in early stages, then angular, about 2 mm diam, orangish red (6A3) when young, then yellowish brown (4B3) to brown (5D4), changing dark blue (6E1) to bluish black (6F1), then blackening (26 F1) slowly when injured; tubes 0.6–1.2 cm in length, pale yellow (1A3) to yellow (2A3), changing blue (21B3) quickly when injured. Stipe 9–11 × 1.8–2.5 cm, central, subcylindrical, solid, usually enlarged at base (3.5–4 cm); surface yellow (1A3) to yellowish brown (1A4), covered with red (7B4) punctuations, sometimes with a thin layer of white pruina in the lower part of stipe; conext yellowish (1A3) to yellow (1A5), changing blue (21B3) quickly when injured. Basal mycelium white. Odor indistinct.

Basidia 31.5–39.5 × 9.5–12.5 μm, clavate, thin- to slightly thick-walled (up to 0.5 μm), 4-spored, colorless to yellowish in KOH; sterigmata 4–5 μm long. Basidiospores [140/7/3] (8–)8.5–10.5(–11) × (3–)3.5–4.5(–5) μm, Q = (2–)2.22–2.86(–3.33), Qm = 2.48 ± 0.22, subfusiform to ellipsoid, yellowish brown in KOH, smooth. Hymenophoral trama boletoid, composed of thin-walled hyphae, yellowish in KOH, 3–8 μm wide. Cheilocystidia 20–38 × 7–10 μm, fusiform or subfusiform, thin-walled, colorless to yellowish in KOH, no encrustations. Pleurocystidia 33–52 × 8–12 μm, fusiform or subfusifom, thin-walled, colorless to yellowish in KOH, no encrustations. Pileipellis a trichoderm 100–110 μm thick, composed of more or less vertically arranged, pale yellowish brown in KOH, thin-walled hyphae 4–6 μm diam; terminal cells 15–55 × 4–6 μm, narrowly clavate or subcylindrical, with obtuse apex. Pileal trama made up of hyphae 4–8 μm diam, slightly thick-walled (up to 0.5 μm), colorless to yellowish in KOH. Stipitipellis a hymeniform about 130 μm thick, composed of thin-walled emergent hyphae, colorless to yellowish in KOH, with clavate, subclavate, fusiform or subfusiform terminal cells (18–47 × 6–9 μm). Stipe trama composed of parallel hyphae 3–10 μm wide, thin-to slightly thick-walled (up to 0.5 μm), yellowish in KOH. Clamp connections absent in all tissues.

Habitat and distribution: Gregarious on the ground in forests dominated by fagaceous trees, and currently known only from southern China (Yinggeling of Hainan Tropical Rainforest National Park, Hainan).

Additional materials examined: CHINA. Hainan Province, Ledong County, Yinggeling Branch of Hainan Tropical Rainforest National Park, Nanfaling, elev. 560 m, 6 May 2018, N.K. Zeng3352 (FHMU3370); same location, 24 Apr 2019, N.K. Zeng4030 (FHMU3371).

Phylogenetically, our specimens were placed into the genus Neoboletus based on a combined data set (28S + ITS + TEF1), and the morphological features of them also match the concept of Neoboletus (Vizzini, 2014; Chai et al., 2019; Gelardi et al., 2019). Moreover, N. infuscatus is genetically distant from other taxa of Neoboletus (Fig. 1).

Morphologically, B. craspedius Massee, possibly a member of Neoboletus, N. luridiformis and N. obscureumbrinus (Hongo) N.K. Zeng, H. Chai & Zhi Q. Liang also have large basidiomata. However, Singaporean B. craspedius has a pileus tinged with reddish, a crimson stipe and sometimes with crimson reticulations at the apex, wider basidiospores measuring 9–11 × 4.5–5 μm, and narrower cystidia (Corner, 1972); N. luridiformis differs from N. infuscatus in a dark brown, reddish brown to yellowish brown pileus, red pores, longer basidiospores measuring (12.8–)13.3–15.5(–16.5) × 4.2–5.5 μm, and a distribution in Europe (Vizzini, 2014); N. obscureumbrinus can be distinguished by a brown to dark brown, subtomentose pileus, a stipe light yellow to dark orange in upper part, brown to brownish orange in lower part, and covered with brown to dark brown scales on the surface, and larger basidiospores measuring 10–12 × 4–5 μm (Wu et al., 2016a). Moreover, N. magnificus (W.F. Chiu) Gelardi, Simonini & Vizzini, N. erythropus var. novoguineensis (Hongo) Blanco-Dios and N. sinensis (T.H. Li & M. Zang) Gelardi, Simonini & Vizzini are somewhat similar to N. infuscatus, however, N. magnificus, a species originally described from Yunnan Province of southwestern China, has a rose red to light red to coffee brown, subtomentose pileus, and staining dark blue quickly when injured, a stipe buttercup yellow to maize yellow at the apex, red to dark red towards the base, staining dark blue quickly when touched, light yellow basal mycelium, and larger basidiospores mearuring (9–)10–13(–15) × 4–5 (–5.5) μm (Wu et al., 2016b); N. erythropus var. novoguineensis has a brown to dark brown, minutely tomentose pileus, a stipe densely covered with red dots with a brown strigose base, larger basidiospores mearuring 9.5–15 × 4–5.5 μm, and a distribution in New Guinea (Hongo, 1973); N. sinensis was also described from Hainan Province of southern China, it can be easily distinguished from N. infuscatus by a cherry red and reticulate stipe, larger basidiospores measuring 13–19 × 5–6.5 μm, and broadly fusiform pleurocystidia (Zang, Li, & Peterson, 2001). The brownish yellow, yellowish brown to pale brown pileus of N. infuscatus is also reminiscent of Japanese B. bannaensis Har. Takah. and Papua New Guinean B. manicus R. Heim, both of them in need of generic placement confirmation (Corner, 1972; Takahashi, 2007), however, B. bannaensis has a context turing rufescent and light blue when injured, short tubes, and smaller basidiospores mearuring 6.5–9 × 3.5–4 μm (Takahashi, 2007); B. manicus has a stipe with red reticulation, pores red orange or crimson when old, and surfaces of pileus and stipe without white pruina when young (Corner, 1972). Although Caloboletus guanyui N.K. Zeng, H. Chai & S. Jiang, a species orginally described from Japan, is not a member of Neoboletus, it shares several common morphological features wtih N. infuscatus. In order to identify the two taxa in the field, herein their morphological features were also compared. According to the descriptions of Chai et al. (2019),C. guanyui differs from N. infuscatus in smaller basidiomata, surfaces of pileus and stipe usually without a layer of pruina, a white context, a stipe densely covered with pale brown, brown to reddish brown squamules, and context in stipe unchanging in color when injured.

Acknowledgments

We are grateful to the forest rangers (Yinggeling Branch of Hainan Tropical Rainforest National Park) for their kind help during the field investigations.

The study was supported by the Hainan Provincial Natural Science Foundation of China (No. 820RC633), and the National Nature Science Foundation of China (Nos. 31760008, 31560005).

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