Marasmioid and Gymnopoid Fungi of the Republic of Korea. 8. Gymnopus Section Levipedes.

Collections of Gymnopus sect. Levipedes from the Republic of Korea have been studied. Two new species, Gymnopus dryophiloides and G. brunneodiscus , are described based on their macro- and micromorphological and phylogenetic characteristics. Three other species, referred to as Gymnopus spp. 1, 2, and 3, are distinguished as separate taxa without formal descriptions. Taxonomic and phylogenetic positions of all taxa have been inferred and confirmed by analyses of ITS and LSU sequence data. Their detailed descriptions, illustrations and an identification key are provided.

Introduction

The genus Gymnopus (Pers.) Roussel belongs to the family Omphalotaceae, and is, according to Antonín and Noordeloos [1], divided into five sections. Species of sect. Levipedes (Fr.) Halling are characterized by a pileipellis composed of inflated, mostly irregular, lobed or coralloid elements (Dryophila-structure). Other Gymnopus sections have a pileipellis in the form of an (ixo)cutis or an irregular trichoderm [1,2]. There are about 45 species described worldwide and their distribution is very broad [1‒8]. However, information from many parts of the world (e.g., Africa, South America) is missing or very incomplete.

None of the species belonging to Gymnopus sect. Levipedes had been recorded in the Republic of Korea until 2011 [9]. Jang et al. [10] published their own Korean sequence called G. dryophilus in the phylogeny tree (but see our results, Table 1, Figure 1).

Table 1.

The list on the GenBank accession number of nrITS and nrLSU sequences used for this study.

Scientific name	Herbarium Number	Locality	GenBank accession Number
			ITS	LSU
Gymnopus alpinus	Duke15	Sweden	DQ480101	–
Gymnopus alpinus	Duke14	U.K., Scotland	DQ480102	–
Gymnopus alpinus	TENN 55,834	U.K., Scotland	DQ480114	–
Gymnopus alpinus	CB 16251	Latvia	JX536168	–
Gymnopus aquosus	TENN 57958	Germany	AY256691	–
Gymnopus aquosus	TENN 55,883	U.K., Scotland	DQ450003	–
Gymnopus aquosus	BRNM 710027	Czech Republic	JX536170	–
Gymnopus aquosus	BRNM 670755	Czech Republic	JX536171	–
Gymnopus aquosus	BRNM 695556	Czech Republic	JX536173	–
Gymnopus aurantiipes	SFSU-AWW118	Java	AY263432	–
Gymnopus bicolor	SFSU-AWW116	Java	AY263423	AY639411
Gymnopus brunneodiscus	BRNM 808974	Korea	MH589971	MH589989
Gymnopus brunneodiscus	BRNM 808971	Korea	MH589972	MH589992
Gymnopus brunneodiscus	BRNM 714974	Korea	MH589973	MH589988
Gymnopus brunneodiscus	BRNM 808976	Korea	MH589974	MH589990
Gymnopus brunneodiscus	BRNM 808975	Korea	MH589975	MH589991
Gymnopus confluens	TENN F-059603	Russia	KP710300	–
Gymnopus confluens	BRNM 734005	Czech Republic	JX536124	–
Gymnopus confluens	TENN F-059603	Sweden	–	KP710313
Gymnopus confluens	GLM 45930	Germany	–	AY207164
Gymnopus dryophilus	TENN 58257	Russia	DQ449963	–
Gymnopus dryophilus	TENN 52412	USA, ID	DQ449964	–
Gymnopus dryophilus	TENN 51438	Canada, NS	DQ449966	–
Gymnopus dryophilus	Duke29		DQ480098	–
Gymnopus dryophilus	BRNM 695586	Czech Republic	JX536143	–
Gymnopus dryophilus	BRNM 712600	Czech Republic	JX536158	–
Gymnopus dryophilus	TENN 57012		–	AY640619
Gymnopus dryophilus	ZRL201566	China	–	KY418871
Gymnopus dryophilus	FO 21603	Germany	–	AF291305
Gymnopus dryophilus	TENN 57012		–	NG027632
Gymnopus dryophilus var. lanipes (isoneotype)	BRNM 670686	Spain	JX536137	–
Gymnopus dryophilus (isoneotype)	DUKE 193411	Sweden	JX536153	–
Gymnopus dryophiloides	KUC20140627-37	Korea	KX513744	–
Gymnopus dryophiloides	BRNM 781446 (specimen)	Korea	MH589959	–
Gymnopus dryophiloides	BRNM 781446 (culture)	Korea	MH589961
Gymnopus dryophiloides	BRNM 781444	Korea	MH589960	–
Gymnopus dryophiloides	BRNM 781448	Korea	MH589962	MH589980
Gymnopus dryophiloides	BRNM 781450	Korea	MH589963	MH589983
Gymnopus dryophiloides	BRNM 718679	Korea	MH589964	-
Gymnopus dryophiloides	BRNM 781451	Korea	MH589965	MH589981
Gymnopus dryophiloides	BRNM 781453	Korea	MH589966	MH589977
Gymnopus dryophiloides	BRNM 781447	Korea	MH589967	MH589985
Gymnopus dryophiloides	BRNM 781452	Korea	MH589970	MH589984
Gymnopus dryophiloides	BRNM 781449	Korea	–	MH589978
Gymnopus dryophiloides	BRNM 781454	Korea	–	MH589979
Gymnopus dryophiloides	BRNM 781456	Korea	–	MH589982
Gymnopus earleae	TENN 59457	USA, OR	AY256694	–
Gymnopus erythropus	SAV XI 2002	Slovakia	DQ449996	–
Gymnopus erythropus	BRNM 705224	Czech Republic	JX536131	–
Gymnopus erythropus	BRNM 664995	Czech Republic	JX536133	–
Gymnopus erythropus	BRNM 693553	Switzerland	JX536135	–
Gymnopus erythropus	GLM 45932		–	DQ071804
Gymnopus fagiphilus	BRNM 712422	Czech Republic	JX536125	–
Gymnopus fagiphilus	BRNM 712407	Czech Republic	JX536126	–
Gymnopus fagiphilus	BRNM 691489	Czech Republic	JX536128	–
Gymnopus hybridus	Dvořák 138/02, BRNU	Czech Republic	JX536175	–
Gymnopus hybridus	Dvořák 393/07, BRNU	Czech Republic	JX536176	–
Gymnopus hybridus	BRNM 695773	Italy	JX536177	–
Gymnopus indoctoides	AWW125		AY263424	AY639419
Gymnopus inusitatus	SCM B-4065	Spain	JN247551	JN247555
Gymnopus inusitatus	SCM B-4057	Spain	JN247552	JN247556
Gymnopus inusitatus	SCM B-4058	Spain	JN247553	JN247557
Gymnopus inusitatus var. cystidiatus	BRNM 737257	Hungary	–	JN247554
Gymnopus junquilleus	TENN 59532	USA, TN	AY256693	–
Gymnopus macropus	TENN 58090	Costa Rica	AF505788	–
Gymnopus macropus	TENN 56636	Costa Rica	DQ449978	–
Gymnopus macropus	TENN 58619	Costa Rica	DQ449979	–
Gymnopus nubicola	NY REH8290	Costa Rica	AF505781	–
Gymnopus ocior	BRNM 728565	Slovakia	JX536160	–
Gymnopus ocior	BRNM 737693	Norway	JX536164	–
Gymnopus ocior	BRNM 699795	Czech Republic	JX536166	–
Gymnopus sepiiconicus	AWW117	Java	AY263448	–
Gymnopus sepiiconicus	AWW126		–	AY639427
Gymnopus subsulphureus	TENN 56718	USA, NC	AY256692	–
Gymnopus subsulphureus	TENN 56321	USA, NC	DQ449972	–
Gymnopus spongiosus	Duke229		DQ480093	–
Gymnopus spongiosus	TENN 59640	USA, Tennessee	DQ480113	–
Gymnopus vitellinipes	AWW115		AY263453	–
Gymnopus sp.1	BRNM 808978	Korea	MH589969	MH589986
Gymnopus sp.2	BRNM 718669	Korea	MH589976	MH589993
Gymnopus sp.3	BRNM 718701	Korea	MH589968	MH589987

Entries in bold type were newly sequenced by the authors.

Figure 1.

Phylogenetic tree for Gymnopus sect. Levipedes based on the nrITS region (ITS1, 5.8S and ITS2) inferred from Bayesian analysis. Specimen names and their GenBank accession numbers in bold letters were newly obtained for this study.

Specimens of Gymnopus sect. Levipedes collected from various localities throughout the Republic of Korea since 2007 are evaluated in this study. This paper is one of a series of papers describing the diversity of marasmioid, marasmielloid, and gymnopoid fungi in the Republic of Korea, supported by the National Institute of Forest Science. Two papers dealing with sections Androsacei and Impudicae of the genus Gymnopus have already been published [11,12].

Material and Methods

Morphology

Macroscopic descriptions of collected specimens are based on fresh basidiomata. Color abbreviations follow Kornerup and Wanscher [13]. The authors of fungal names are cited according to the International Plant Names Index Authors website (http://www.ipni.org/ipni/authorsearchpage.do). Microscopic features were studied using dried material mounted in H2O, approximately 5% KOH, Melzer’s reagent, and Congo Red (for recipes, see [14]) using an Olympus BX-50 light microscope (Tokyo, Japan) at 1000× magnification. For lamellae, L refers to the number of entire lamellae, while l refers to the number of lamellulae tiers between each pair of entire lamellae. For basidiospores, the factor E indicates the quotient of the length and width in any one basidiospore and Q is the mean of the E-values; the basidiospore values are based on 20 measurements in each collection. Specimens are preserved in the herbarium of the Moravian Museum, Brno, Czech Republic (BRNM). Cultures are housed in the herbarium of the National Institute of Forest Science (NIFoS), Republic of Korea.

Phylogenetic analyses

DNA extraction was performed by means of the modified method by Lee and Taylor [15]. The PCR primer used ITS1F, ITS1, ITS4B and ITS4 for the nuclear ribosomal internal transcribed spacer (nrITS) region and selected LR0R, and LR7 for the nuclear large subunit ribosomal DNA (nrLSU) region according to Gardes and Bruns [16]. PCR cycling condition and DNA sequencing was carried out according to the protocol described by Antonín et al. [12,17]. For the nrITS region, PCR was performed with a 30 s denaturation at 94 °C, a 30 s annealing at 56 °C and a 1 min extension at 72 °C and was run with 35 cycles in the first denaturation and the last extension. For the nrLSU region, PCR was carried out with a 30 s denaturation at 94 °C, a 45 s annealing at 45 °C and a 90 s extension at 72 °C and then 35 cycles were run with the first denaturation and the last extension. Forty nrITS sequences of 19 species and 12 nrLSU sequences of eight species belonging to section Levipedes were retrieved from GenBank [4,5,18]. Eighteen sequences of the nrITS dataset and 17 sequences of the nrLSU dataset were formed for this study. Gymnopus confluens belonging to section Vestipedes was selected as an outgroup [18]. GenBank accession numbers of all sequences for the phylogenetic trees are listed in Table 1. Both the nrITS and nrLSU datasets were aligned with Mega 6.06 [19] and Clustal X2 [20]. Each phylogenetic analysis was performed by MrBayes 3.1.2. [21]. In the nrITS and nrLSU datasets, the ends of them were trimmed to 714 and 882 characters including 492 and 796 constant, and 188 and 46 variable sites, respectively. Both Markov chains were run for 2,000,000 generations with a sample taken every 100th generation, discarding a burn-in of 1,000 generations. The general time reversible (GTR) was used with gamma-distributed substitution for a given data set. The Bayesian branch supports were assigned as posterior probabilities (PP) according to the 50% majority-rule of the consensus trees. The PP values showed to be higher than 0.95, including 95% confidence intervals (CI).

Results

The two newly described species, Gymnopus dryophiloides and G. brunneodiscus, and Gymnopus spp. 1, 2 and 3, are distinguished from morphologically similar species by phylogenetic analyses of nrITS and nrLSU (Figures 1 and 2). In two phylogenetic trees, taxa of the Gymnopus dryophilus complex collected in Korea showed a monophyletic clade (95% and 98%), and formed one other clade close to European and American taxa with high supporting values (100% and 100%). This clade is described as a new species, G. dryophiloides. In the nrITS region, this species have a sequence divergence of 1.3% and differ in 9 out of 714 nucleotide sequences from typical G. dryophilus (isolate; AFTOL_ID 559, GenBank; DQ241781). In the nrLSU region, this new species has different sequences within 3 bp among 822 bp in several isolations from other localities (China, Germany, USA). In the monoclade including holotype G. dryophiloides, the nrITS sequence (MH589967) of the G. dryophiloides holotype differs the only 1 bp from KX513744, 2 bp with MH589958, and the nrLSU sequences have the same base pair. Gymnopus brunneodiscus differs in 42 out of 714 nucleotide characters of the nrITS dataset from G. ocior (Pers.) Antonín & Noordel. They have a sequence divergence of about 5.9%. The independent taxonomic positions of Gymnopus spp. 1 and 2 are supported by the nrITS and nrLSU sequences. Gymnopus sp. 1 and five sequences of G. aquosus (Bull.: Fr.) Antonín & Noordel. form one clade and differ in 7 nucleotide sites, although the two species are morphologically different. In the nrITS dataset, Gymnopus sp. 3 forms a group with G. erythropus (Pers.: Fr.) Antonín, Halling & Noordel., G. earleae Murrill, G. fagiphilus (Velen.) Antonín, Halling & Noordel., G. hybridus (Kühner & Romagn.) Antonín & Noordel., G. inusitatus (Vila & Llimona) Vila & Llimona, G. spongiosus (Berk. & M.A. Curtis) Halling, and G. vitellinipes A.W. Wilson, Desjardin & E. Horak. This species forms also a significantly distant branch with G. earleae according to 20 base substitutions with 714 base pairs of nrITS sequences and has a sequence divergence of 2.8%.

Figure 2.

Phylogeny of Gymnopus sect. Levipedes based on the nrLSU (nuclear large subunit of ribosomal RNA gene) inferred from Bayesian analysis. Specimen names and their GenBank accession numbers in bold letters were newly sequenced for this study.

Taxonomy

Species descriptions

MycoBank MB 828254

Diagnosis: Gymnopus dryophiloides differs from G. dryophilus by a more distinct orange tinge of the stipe, slightly smaller (shorter) basidiospores, shorter cheilocystidia with a larger variability in shape, and forms an independent monoclade in the ITS and LSU dataset. Gymnopus dryophiloides is characterized by a pale to light yellow, orange or watery ochraceous yellow pileus. It has yellowish white lamellae, a pale to light yellow or orange stipe, (4.0)4.5–6.0(6.5) × 2.5–3.5(4.0) μm large basidiospores, and 17–38(50) × 4.5–10(17) μm large, clavate, (sub)cylindrical, fusoid, mostly lobate, irregular to coralloid cheilocystidia (Figures 3 and 4).

Figure 3.

Basidiomata. (A) Gymnopus dryophiloides (holotype, BRNM 781447); (B) G. dryophiloides (BRNM 781452); (C) G. brunneodiscus (holotype: BRNM 808975); (D) Gymnopus sp. 3 (BRNM 718701); (E) Gymnopus sp. 1 (BRNM 808978); (F) Gymnopus sp. 2 (BRNM 718669).

Figure 4.

Gymnopus dryophiloides (BRNM 781447). (A) cheilocystidia; (B) basidiospores; (C) pileipellis cells. Scale bar = 20 μm.

Holotype: Republic of Korea. Mt. Kariawangsan, Dae-hwa-myeon, Pyeonchang, 37°28′32″N, 128°30ˊ11″E, alt. c. 1060‒1080 m, 21 August 2012, V. Antonín 12.138 & K.-H. Ka (BRNM 781447, designated here).

Basidiomata single. Pileus 10‒50 mm broad, convex to conical-convex with involute margin when young, then conical-convex to plano-convex with less distinct to absent broad umbo and inflexed to straight margin, often uplifted and undulate when old, hygrophanous, striate only at outer margin or not translucently striate, smooth or slightly rugulose, glabrous, pale to light yellow or orange (4‒5A3‒6, 6 A‒B5) or watery ochraceous yellow when moist, light yellow to yellowish white (3‒4A2‒3) when dry. Lamellae very close, L = (35)50‒60, l = 3–4(6), emarginate and attached with small tooth, narrow, whitish then yellowish white (3A2‒3(4)), with a concolorous, finely denticulate and pubescent edge. Stipe 30‒75 × 1.5‒5 mm, cylindrical or laterally compressed (sometimes with groove), slightly broadened at apex, slightly broader to subbulbose (up to 10 mm) at base, bulba more distinct in young basidiomata, glabrous or finely pruinose at apex, smooth or finely longitudinally fibrillose, concolorous with lamellae at apex, pale to light yellow or orange (4‒5A3‒6), sometimes darker, light orange or grayish orange (5A4, 6B6) in old basidiomata; with whitish to pale (pinkish) ochraceous basal rhizoids. Context membranaceous, concolorous with surface of basidiomata, hollow in stipe, with slightly fungoid smell and mild taste, sometimes with slightly acrid aftertaste.

Basidiospores (4.0)4.5–6.0(6.5) × 2.5–3.5(4.0) µm, average = 5.3 × 3.1 µm, E = 1.50–2.40, Q = 1.70‒1.86, ellipsoid, ellipsoid-fusoid, pip-shaped, hyaline, thin-walled. Basidia 17–23(25) × 5.0–7.5 µm, 4-spored, clavate, sometimes subcapitate. Basidioles 12–25 × 3.0–8.0(9.0) µm, subcylindrical, clavate (and sometimes subcapitate), fusoid. Cheilocystidia 17–38(50) × 4.5–10(17) µm, variable in shape, clavate, (sub)cylindrical, fusoid, mostly lobate, irregular to coralloid, thin-walled. Pleurocystidia absent. Trama hyphae cylindrical or subinflated, ± thin-walled, branched, smooth or minutely incrusted, 4.0‒15 µm wide. Pileipellis composed of cells forming a Dryophila-structure, up to 80 × 5.0‒25 µm in size, cylindrical, fusoid or clavate, irregular, lobate, branched, subcoralloid, thin- to slightly thick-walled, smooth or incrusted, pale (dirty) yellow-brown in KOH. Pileocystidia absent. Stipitipellis a cutis of cylindrical, parallelly arranged, slightly thick-walled, smooth, up to 6.0 µm wide hyphae. Caulocystidia absent, scattered cylindrical, thin-walled terminal cells present. Clamp connections present in all tissues.

Ecology: On detritus and litter of Abies holophylla, Acer sp., Castanea crenata, Juglans mandshurica, Larix campestris, Pinus densiflora, P. koraiensis, P. rigida, Quercus acutissima, Q. mongolica, Q. serrata, Quercus sp. and Zelkova serrata.

Etymology: dryophiloides = similar to G. dryophilus.

Additional Specimens Examined: Republic of Korea. Inje, Buk-myeon, Seoraksan National Park, 38°09′51″N, 128°22′23″E, alt. c. 480 m, 27 June 2008, V. Antonín 08.39 (BRNM 718679); Chuncheon, Dongsan-myeon, Bongmyong-ri, 20 August 2007, R. Ryoo KG 139 (BRNM 781444); Deogyusan National Park, Cheon-yeon falls, 24 August 2007, R. Ryoo KG 158 (BRNM 781446); Deogyusan National Park, Chilyeon falls, 23 August 2007, R. Ryoo KG 153 (BRNM 781446); Cheongju, Songnisan-maltijae Recreational Forest, 37°29′33″N, 127°46′43″E, alt. c. 230 m, 27 August 2015, V. Antonín 15.106, K.-H. Ka, S.-K. Kim & J.-A. Kang (BRNM 781451); Chungju, Joryeongsan Natural Forest, 36°48′43″N, 128°02′43″E, alt. c. 495 m, 28 August 2015, V. Antonín 15.117, K.-H. Ka, S.-K. Kim & J.-A. Kang (BRNM 781452); Chungju, Bonghwang Nature Forest, 37°03′20″N, 127°49′46″E, alt. c. 115 m, 29 August 2015, V. Antonín 15.125, K.-H. Ka, S.-K. Kim & J.-A. Kang (BRNM 781453); Youngdong, Mt. Minjooji Recreational Forest, 36°03′12″N, 127°49′50″E, alt. c. 620 m, 26 August 2015, V. Antonín 15.97, K.-H. Ka, S.-K. Kim & J.-A. Kang (BRNM 781450); Wonju, Mt. Chiaksan, 37°25′24″N, 128°04′16″E, alt. c. 290 m, 27 August 2015, V. Antonín 15.75, K.-H. Ka, S.-J. Yeong & E.-J. Wang (BRNM 781449); Jecheon, recreational forest, 37°08′42″N, 128°02′03″E, alt. c. 350 m, 21 August 2015, V. Antonín 15.65, K.-H. Ka, S.-J. Yeong & E.-J. Wang (BRNM 781448); Muju, Mt. Deogyu Recreational Forest, 35°54′26″N, 127°48′39″E, alt. c. 750 m, 30 August 2016, V. Antonín 16.130, K.-H. Ka & S.-H. Kim (BRNM 781454); ibid., 5 September 2016, V. Antonín 16.155, R. Ryoo, K.H. Wang & Y.S. Jang (BRNM 781456); Jangsu, Waryong National Recreational Forest, 35°40′45″N, 127°28′37″E, alt. 570 m, 1 September 2016, V. Antonín 16.145, K.-H. Ka & S.-H. Kim (BRNM 781455); Gyeongnam Prov., Geochang-gun, Geumwonsan Natural Recreational Forest, 35°43′55″N, 127°47′52″E, alt. 480 m, 11 July 2017, V. Antonín 17.25, K.-H. Ka, R. Ryoo & M.-H. Jeon (BRNM 808970).

Remarks: Gymnopus dryophiloides is characterized by having a small, light to grayish orange pileus, a light yellow to light orange, at base subbulbose stipe, small basidiospores, clavate, subcylindrical, fusoid, mostly lobate, irregular to coralloid cheilocystidia, and a pileipellis of the Dryophila-structure. A collection from Dongsan-myeon, Chuncheon (BRNM 781444) differs by smaller, broadly clavate, fusoid, utriform, only more or less regular cheilocystidia, and a collection from Deogyusan National Park, Chilyeon falls (BRNM 781446) also by mostly clavate, regular cheilocystidia.

MycoBank MB 828304

Diagnosis: Gymnopus brunneodiscus differs from G. ocior by a light brown to (chestnut) brown pileus with a paler, almost whitish margin, a pale brown stipe with an orange to orange-brown tinge, and larger cheilocystidia, forming an independent clade in the nrITS and nrLSU phylogeny. Pileus of G. brunneodiscus translucently striate, light brown to (chestnut) brown, with almost whitish margin; stipe pale brown with orange tinge to orange-brown with yellowish white apex; basidiospores (4.7)5.0–7.0 × 2.7–4.0 µm, average = 5.6 × 3.3 µm; cheilocystidia 18–68 × 3.5–6.0(8.0) µm, cylindrical, (narrowly) clavate, irregular, lobed, branched to coralloid; pileipellis of the Dryophila-structure Figures 3 and 5.

Figure 5.

Gymnopus brunneodiscus (BRNM 714970). (A) cheilocystidia; (B) basidiospores; (C) pileipellis cells. Scale bar = 20 μm.

Holotype: Republic of Korea. Tean, Mt. Baekhwa, 36°46′16″N, 126°18′54″E, alt. c. 100 m, 10 July 2014, V. Antonín 14.73 & K.-H. Ka (BRNM 808975, designated here).

Basidiomata single or in groups. Pileus 15–38 mm broad, convex-conical to low convex when young, then almost applanate with ± plane center or with indistinct umbo in small central depression and inflexed, later inflexed to straight margin, hygrophanous, (slightly) translucently striate up to half of the pileus, smooth, glabrous, light brown to (chestnut) brown (6 C–D5 to 7 D–F6‒7 or 7‒8E‒F7), with paler, almost whitish margin (especially when young), drying out to pale yellow or light yellow (± 4A3–4); the pale margin seems to be a constant character. Lamellae close, L = 25–45, l = 3–6, emarginate and attached with tooth, ±horizontal, slightly intervenose, pale yellowish white (3–4A2), sometimes with brownish tinge when young, with concolorous, finely pubescent edge. Stipe 35–70 × 1–3 mm, cylindrical, sometimes slightly broadened at base (up to 8 mm), slightly broadened above, smooth, glabrous except for finely pruinose apex, pale brown with orange to orange-brown tinge (7‒8 C‒E7), apex paler, yellowish white (4A3) when young; with dirty whitish or pale brownish basal tomentum. Context concolorous with surface of basidiomata, hollow in stipe, whitish in pileus, without a special smell and with a mild taste.

Basidiospores (4.7)5.0–7.0 × 2.7–4.0 µm, average = 5.6 × 3.3 µm, E = (1.4)1.6–2.2, Q = (1.5)1.7‒1.9, ellipsoid-fusoid, ellipsoid, hyaline, thin-walled. Basidia 20‒25 × 5.5‒7.0 µm, 4-spored, clavate. Basidioles 12–28 × 3.0–7.5 µm, cylindrical, clavate, fusoid. Cheilocystidia 18–68 × 3.5–6.0(8.0) µm, cylindrical, (narrowly) clavate, irregular, lobed, branched to coralloid, thin-walled. Pleurocystidia absent. Trama hyphae cylindrical or subinflated, thin- to slightly thick-walled, branched, smooth or less frequently minutely incrusted, hyaline, 3.0‒15 µm wide. Pileipellis composed of cells forming a Dryophila-structure, cells often relatively slender, irregular, lobate to coralloid, smooth or incrusted, ± thin-walled, 3.0–15 µm wide; incrustation ± hyaline (margin) to (dark) brown (center) in KOH. Pileocystidia absent. Stipitipellis a cutis of cylindrical, parallelly arranged, slightly thick-walled, smooth or minutely incrusted, 3.0‒5.0(6.0) µm wide hyphae. Caulocystidia absent; scattered adpressed to suberect, clavate to cylindrical, ± thin-walled terminal cells present. Clamp connections present in all tissues.

Ecology: On detritus of Larix sibirica, Pinus densiflora, Acer palmatum, Ailanthus glandulosa, Castanea crenata, Quercus mongolica and Quercus sp. in mixed forests.

Etymology: brunneus = brown, discus = disk. Having a brown-colored pileus center.

Additional Specimens Examined: Republic of Korea. Chuncheon, Dongsan-myeon, Experimental forest of Kangwon National University, 37°46′46″N, 127°48′59″E, alt. c. 210 m, 22 July 2007, V. Antonín 07.102, H.D. Shin & R. Ryoo (BRNM 714970); Ibid., V. Antonín 07.108, H.D. Shin & R. Ryoo (BRNM 714974); Cheongju, Sangdang-sanseong Natural Recreational Forest, 36°40′48″N, 127°32′40″E, alt. c. 180 m, 27 August 2015, V. Antonín 15.112, K.-H. Ka, K.-S. Kim & J.A. Kang (BRNM 808971); Hongcheon, Dong-myeon, 37°41′07″N, 128°00′06″E, alt. 285 m, 17 August 2013, V. Antonín 13.175 & R. Ryoo (BRNM 808972); ibid., 37°42′08″N, 128°00′06″E, alt. c. 580 m, 17 August 2013, V. Antonín 13.173 & R. Ryoo (BRNM 808973); ibid., 37°41′10″N, 128°00′02″E, alt. c. 310 m, 17 August 2013, V. Antonín 13.180 & R. Ryoo (BRNM 808974); Tean, Anmyeon-do, 36°29′47″N, 126°21′36″E, alt. 40 m, 11 July 2014, V. Antonín 14.83 & K.-H. Ka (BRNM 808976); Chungju, Joryeongsan Natural Forest, 36°48′43″N, 128°02′43″E, alt. 495 m, 28 August 2015, V. Antonín 15.115, K.-H. Ka, S.-K. Kim & J.-A. Kang (BRNM 808977).

Remarks: Gymnopus brunneodiscus is characterized by having a light to dark brown pileus with a paler margin (which seems to be a constant character), closely placed yellowish white lamellae, a smooth and glabrous stipe, (4.7)5.0–7.0 × 2.7–4.0 µm large basidiospores, and cylindrical, (narrowly) clavate, irregular, lobed to coralloid cheilocystidia. Our collection from Tean, Anmyeon-do (BRNM 808976) differs by having smaller basidiospores ((4.2)4.5‒5.5(6.0) × 2.5‒3.2 µm), and shorter cheilocystidia (18‒35 × 4.0‒7.0 µm).

Key to species of Gymnopus sect. Levipedes collected in the Republic of Korea

Pileus ochraceous to (chestnut) brown, with constantly almost whitish outer margin; cheilocystidia 18–65 × 3.5–6.0(8.0) µm, cylindrical, (narrowly) clavate, irregular, lobed, branched to coralloid; pileipellis of the typical Dryophila-structure...................................Gymnopus brunneodiscus

1*.Pileus white, light to grayish orange or watery ochraceous yellow, ochraceous brownish, light or grayish orange; cheilocystidia up to 38(50) × 4.5–13(17) µm, more distinctly clavate; pileipellis of the typical Dryophila-structure or transient to a cutis.................................................................................2

Pileus milky white to pale yellow-white with irregularly dispersed brown stains; stipe whitish to pale yellowish ochraceous; basidiospores (6.0)6.5‒7.0(7.5) × 3.5‒4.0(4.5) µm, average 6.7 × 3.9 µm.................................................Gymnopus sp. 3

2*.Pileus light to grayish orange or watery ochraceous yellow, ochraceous brownish, light or grayish orange; stipe light yellow to light orange, pale brownish or (orange) brown; basidiospores (4.0)4.5‒6.5 × 2.5‒3.5(4) µm, average less than 6.0 × 3.1 µm............................................................3

Pileipellis of the typical Dryophila-structure; pileus light to grayish orange or watery ochraceous yellow; stipe light yellow to light orange, sometimes darker in old basidiomata; basidiospores (4.0)4.5–6.0(6.5) × 2.5–3.5(4.0) µm, average = 5.3 × 3.1 µm; basidia 17‒23(25) µm long................................................Gymnopus dryophiloides

3*.Pileipellis transient between the Dryophila-structure and a cutis; pileus ochraceous brownish, paler toward margin, light or grayish orange; stipe pale cream and (orange) brown toward base or pale brownish; basidiospores 5.0–6.5 × 2.7–3.5 µm, length more than 5.3 µm on average; basidia 16‒21 µm long..............................4

Pileus orangish ochraceous; stipe pale brownish with paler apex; basidiospores 5.0‒6.0(6.5) × 2.7‒3.5 µm, average 5.6 × 3.1 µm, Q = 1.83............................. Gymnopus sp. 1

4*.Pileus ochraceous brownish at center, pale cream at margin; stipe pale cream at apex, (orange) brown toward base; basidiospores 5.5‒6.5 × (2.5)2.7‒3.2(3.5) µm, average 6.0 × 3.0 µm, Q = 2.03.......................Gymnopus sp. 2

Discussion

Species of Gymnopus sect. Levipedes from the Republic of Korea have been distinguished based on their macro- and micromorphology and molecular characteristics. The phylogenetic position of Gymnopus dryophilus complex is similar in nrITS and nrLSU to that published in previous papers [5,18] but the Korean collections form an independent clade, a new species, G. dryophiloides. This study shows that G. nubicola Halling is a part of the G. dryophilus group in the nrITS phylogeny, although it has morphologically different characters [5]. The separate positions of G. brunneodiscus, Gymnopus spp. 1, 2 and 3 have been confirmed based on their morphological and molecular characterization. Although Gymnopus spp. 1, 2 and 3 represent both morphologically and phylogenetically separate new species, the collected material (only one collection, sometimes only one basidioma) is too poor for formal descriptions of these taxa.

Gymnopus dryophiloides is morphologically and phylogenetically closely related to G. dryophilus, a species widely distributed throughout Europe [1]. It differs by a more distinct orange tinge of the stipe, sometimes distinctly yellow lamellae, slightly smaller (shorter) basidiospores and shorter cheilocystidia with a greater variability in shape [1,18]; for a detailed comparison, see Table 2. According to our phylogenetic studies, it seems that North American collections also form a separate clade. Gymnopus nubicola, described from Ecuador, should differ by a dark reddish brown pileus when young and fresh, eventually becoming brown to light brown, occasionally becoming grayish orange and then mostly at the margin, flesh with a pungent, almost waxy smell, and a mild to waxy taste, a brown to dark brown stipe toward base, and small, 10‒20 × 3‒5 µm, scattered and inconspicuous, irregularly lobed and knobbed cheilocystidia [3]. However, the phylogenetic placement of this collection supports the proposal by Matta et al. [5] to consider it merely a form of an (American) type of “G. dryophilus”. Gymnopus sp. 2 (Yangyang, Micheongol Natural Resort Forest, 26 June 2008, V. Antonín 08.29, BRNM 718669, Figures 3 and 6) differs by a centrally ochraceous brownish and marginally pale cream pileus, an (orange) brown stipe toward base, larger basidiospores, 5.5‒6.5 × (2.5)2.7‒3.2(3.5) µm, Q = 2.03, shorter basidia (18‒21 × 5.5‒7.5 µm) and a pileipellis forming a transition between a Dryophila-structure and a cutis. Gymnopus sp. 3 (Hamyang, Macheon-myeon, 8 July 2008, V. Antonín 08.72 & R. Ryoo, BRNM 718701, Figures 3 and 7) differs by a milky white to pale yellow-white pileus with irregularly dispersed brown stains, brown stained lamellae, larger basidiospores, (6.0)6.5‒7.0(7.5) × 3.5‒4.0(4.5) µm, and smaller cheilocystidia (23‒30 × 6.0‒10 µm).

Table 2.

Differential macro- and micromorphological characters of G. dryophiloides against similar species.

	G. dryophiloides	G. dryophilus [1,18]
Pileus	pale to light yellow or orange or watery ochraceous-yellow	pale colored, orange-brown or ochraceous brown, then ochraceous-brown, yellow-ochraceous to pinkish ochraceous
Lamellae	whitish then yellowish white	white, cream to yellow
Stipe	30‒75 × 1.5‒5 mm, concolorous with lamellae at apex, pale to light yellow or orange, sometimes darker, light orange or grayish orange	30‒120 × 1‒5 mm, yellowish with paler apex, sometimes somewhat darker ochraceous brown in basal part
Basidiospores	(4.0)4.5–6.0(6.5) × 2.5–3.5(4.0) μm	5.0–7.0(8.0) × (2.5)3.0–4.0(4.5) μm
Cheilocystidia	17–38(50) × 4.5–10(17) μm, variable in shape, clavate, (sub)cylindrical, fusoid, mostly lobate, irregular to coralloid	17–55 × 4.0–10 μm, (sub)cylindrical, narrowly clavate, mostly coralloid, also lobate or with apical projections

Figure 6.

Gymnopus sp. 1 (BRNM 808978). (A) cheilocystidia; (B) basidiospores; (C) pileipellis cells. Scale bar = 20 μm.

Figure 7.

Gymnopus sp. 2 (BRNM 718669). (A) cheilocystidia; (B) basidiospores; (C) pileipellis cells. Scale bar = 20 μm.

The clade formed by Gymnopus brunneodiscus has 1.00 posterior probabilities and shows one independent group phylogenetically. Gymnopus ocior differs by a dark red- or orange-brown pileus sometimes with yellowish or yellow-red (never whitish) margin, a yellow to ochraceous or reddish brown stipe and smaller, 12‒45 × 3.0‒9.0 µm cheilocystidia [1,18]. In the original description of Gymnopus sepiiconicus (Corner) A.W. Wilson, Desjardin & E. Horak, Corner [22] mentioned smaller basidiomata (pileus up to 18 mm wide, stipe up to 50 × 1.5 mm), and slightly smaller basidiospores (4.5–6 × 2.7–3.5 µm). According to Wilson et al. [4], the Indonesian collections of G. sepiiconicus differ by slightly different basidiospores (4.8–6.4 × 2.4–4.4 µm) and shorter cheilocystidia (20–44 × 3–7 µm), G. alpinus (Vilgalys & O.K. Mill.) Antonín & Noordel. has a dark brown pileus and larger, (6.2)6.5‒8.5 × 3.0‒4.4 µm basidiospores and differently shaped cheilocystidia [1]. Gymnopus bicolor A.W. Wilson, Desjardin & E. Horak also has a distinctly paler margin, but has larger, 5.2‒8.0 × 2.4‒3.6 µm basidiospores and differently shaped cheilocystidia [4]. Gymnopus earleae Murrill has a dark brown pileus, but differs by a basally brown stipe, smaller basidiospores (5.6‒6.4 × 2.8‒3.5 µm) and smaller, usually absent or inconspicuous (and then 24.5‒30 × 2.0‒2.8 µm) cheilocystidia [6]; for a comparison, see Table 3. Gymnopus sp. 1 (Hocheong, 4 Jul 2014, V. Antonín 14.45, R. Ryoo & K.-H. Ka, BRNM 808978, Figures 3 and 8) differs by an almost entirely orangish ochraceous pileus with a paler outer margin, yellow lamellae, a pale brownish stipe, smaller basidiospores, 5.0‒6.0(6.5) × 2.7‒3.5 µm, and smaller, 14‒30 × 6.0‒11(13) µm, clavate, subcylindrical cheilocystidia, which are only irregular, lobate or with projection(s).

Table 3.

Differential macro- and micromorphological characters of G. brunneodiscus against similar species.

	G. brunneodiscus	G. ocior [1,18]	G. sepiiconicus [4]	G. alpinus [1,18]	G. bicolor [4]	G. earleae [2]
Pileus	Light brown to (chestnut) brown, with paler, almost whitish margin	Dark red- or orange-brown, pallescent to reddish yellow or pinkish brownish	Brown to dark brown with beige yellow to white margin in age	Very dark red- to purplish brown, uniform, or only slightly paler at very margin	Brown with beige white margin	Dark brown when young and fresh, fading to an orangish buff
Lamellae	Pale yellowish white, sometimes with brownish tinge when young	Whitish or yellowish lamellae	White	White or cream colored	White	Pale orangish yellow, becoming orangish buff
Stipe	35–70 × 1–3 mm, pale brown with orange tinge to orange-brown, with paler, yellowish white apex when young	20‒60 × 2‒5 mm, yellow to ochraceous or reddish brown	40‒52 × 1‒2 mm, brownish orange to brown or creamy buff, with orange beige apex	30‒60 × 2.5‒6 mm, pale yellow at apex, orange-yellow to orange-brown below	30‒42 × 2‒3 mm, reddish brown, becoming pale orange‒brown, with white beige apex	22‒40(50) × 1‒2(4) mm, orangish buff when young, becoming yellowish orange (ochraceous orange) at the apex and a tawny brown below with age
Basidiospores	(4.7)5.0–7.0 × 2.7–4.0 μm	(5.0)5.5–6.5(7.0) × (2.5)2.75–3.5(4.0) μm	4.8–6.4 × 2.4–4.4 μm	(6.2)6.5–8.5 × 3.0–4.4 μm	5.2‒8.0 × 2.4‒3.6 µm	5.6‒7 × 2.8‒3.5 µm
Cheilocystidia	18–68 × 3.5–6.0(8.0) μm, cylindrical, (narrowly) clavate, irregular, lobed, branched to coralloid,	16–60 × 6.0–12 μm, clavate, subcylindrical or subutriform, often lobed, branched, coralloid or with apical projections	20–44 × 3–7 μm, irregularly cylindrical to obtuse clavate, contorted, lobulate	16.5‒30(44) × 6.0‒11.5 µm, clavate, simple, irregular to coralloid	17.5‒25.5 × 6.5‒9.5 µm, broadly clavate, lobulate, smooth	usually absent, inconspicuous and rare when present, often collapsed, 24.5‒30 × 2.0‒2.8 µm, narrowly cylindric to flexuous contorted, rarely diverticulate

Figure 8.

Gymnopus sp. 3 (BRNM 718701). (A) cheilocystidia; (B) basidiospores; (C) pileipellis cells. Scale bar = 20 μm.