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Research Article
Updated taxonomy on Gerronema (Porotheleaceae, Agaricales) with three new taxa and one new record from China
expand article infoQin Na, Yaping Hu§, Hui Zeng|, Zhizhong Song, Hui Ding§, Xianhao Cheng, Yupeng Ge
‡ Ludong University, Yantai, China
§ Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing, China
| Fujian Academy of Agricultural Sciences; National and Local Joint Engineering Research Center for Breeding & Cultivation of Features Edible Fungi, Fuzhou, China
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Abstract

Only three Gerronema (Porotheleaceae) species have been previously recorded in China. Here, we report collections of a fourth species in China: G. nemorale Har. Takah., which is widely distributed in Chinese temperate to subtropical zones. We also formally describe three new species, collected from Anhui, Fujian, and Zhejiang provinces: G. baishanzuense sp. nov., G. microcarpum sp. nov., and G. zhujian sp. nov. Furthermore, we include the results of a phylogenetic analysis of Porotheleaceae based on a multi-locus (ITS + nLSU) dataset. The results, which indicate that Gerronema is polyphyletic, support the taxonomic recognition of the three new species. Morphological descriptions, photographs, line drawings, and comparisons with closely related taxa are presented for the new and newly recorded species. A key to the seven species of Gerronema in China is also provided.

Keywords

new taxon, polygenes, taxonomy, white-spored

Introduction

Gerronema Singer is a small omphalinoid genus, principally subtropical to tropical in distribution, with approximately 62 named species in Index Fungorum. Singer (1951) erected the genus Gerronema to accommodate three tenacious and lignicolous omphalinoid to clitocyboid species from South America and later transferred some species traditionally placed in Omphalina Quél. to this new genus (Singer 1964). This taxonomic definition of Gerronema was controversial, however, as the circumscription of Omphalina by Singer was notably different from that of Bigelow (Bigelow 1970; Singer 1986). Virtually all species of Omphalina recognized by Bigelow were included in Singer’s concept of Gerronema, whereas species placed in Clitocybe (Fr.) Staude by Bigelow were retained in Omphalina by Singer (Bigelow 1970, 1982, 1985; Singer 1986). Furthermore, Lange (1981) treated Gerronema as a subgenus of Omphalina (subgen. Gerronema). Both Singer and Bigelow considered Gerronema to be pigment based and therefore emphasized pigmentation as a more important taxonomic character than other observed features (Bigelow 1970, 1982, 1985; Singer 1986). Gerronema sensu Singer, however, was considered to be heterogeneous (Clémençon 1982; Moser 1983; Kuyper 1986; Singer 1964, 1975, 1986; Norvell et al. 1994; Antonín et al. 2008), and Redhead (1986) restricted the genus to species having sarcodimitic tissues, a concept supported by Norvell et al. (1994). Along with Redhead, Norvell et al. defined Gerronema as comprising lignicolous species with typical sarcodimitic tissues, and the genus was monophyletic according to this circumscription (Redhead 1986; Norvell et al. 1994). Finally, an infrageneric classification proposed by Singer divided Gerronema into four subgenera containing six sections on the basis of pigmentation, cystidia, hymenophoral trama, and clamp connections (Singer 1970).

In previous taxonomic studies, many authors have suggested that the genus Gerronema is heterogeneous (Clémençon 1982; Moser 1983; Kuyper 1986; Antonín et al. 2008). The polyphyletic status of Gerronema is uncertain, however, owing to insufficient species representation and limited phylogenetic evidence, and only four Gerronema taxa have been analyzed in phylogenetic studies: G. chrysophyllum (Fr.) Singer, G. strombodes (Berk. & Mont.) Singer, G. subclavatum (Peck) Singer ex Redhead, and G. marchantiae Singer & Clémençon (Lutzoni 1997; Pine et al. 1999; Hibbett and Binder 2002; Moncalvo et al. 2002; Redhead et al. 2002). Two of these species, G. chrysophyllum and G. marchantiae, have since been transferred to Chrysomphalina Clémençon (Clémençon 1982) and Loreleia Redhead, Moncalvo, Vilgalys & Lutzoni (Redhead et al. 2002), respectively, and the other two species, G. subclavatum and G. nemorale, are difficult to distinguish genetically (Antonín et al. 2008). According to a phylogenetic reconstruction of more than 800 euagaric taxa derived from a nuclear ribosomal large subunit RNA gene (nLSU) sequence dataset, Gerronema is monophyletic and belongs to the “hydropoid” clade together with Hydropus Kühner ex Singer s. str., Megacollybia Kotl. & Pouzar, Clitocybula (Singer) Singer ex Métrod, and Porotheleum fimbriatum (Pers.) Fr. (Moncalvo et al. 2002). Matheny et al. (2006) and Antonín et al. (2019) concurred with Moncalvo et al. (2002) in the establishment of the hydropoid group and the monophyly of Gerronema. Matheny et al. (2006) also included Henningsomyces candidus (Pers.) Kuntze, Hydnopolyporus fimbriatus (Cooke) D.A. Reid, and some Mycena species (M. auricoma Har. Takah., M. amabilissima (Peck) Sacc. and M. aurantiidisca (Murrill) Murrill) in the same subclade of the large Marasmioid clade, but they did not include any Gerronema species in their studies. In a taxonomic and phylogenetic study of Clitocybula s. l., the hydropoid clade was found to comprise eight genera, including Gerronema, and was sister to other genera (Antonín et al. 2019). In 2019, Vizzini et al. assigned the hydropoid clade to Porotheleaceae, a new family; at the same time, they recognized Gerronema as polyphyletic on the basis of previous taxonomic studies and divided it into seven clades, designated as Gerronema 1 to Gerronema 7 (Vizzini et al. 2019). The view of Gerronema as polyphyletic is also supported by our studies.

Gerronema is well characterized by its lignicolous habit; omphalinoid to clitocyboid basidiomata; an umbonate or infundibuliform pileus with partly to entirely pigmented, decurrent lamellae; smooth, thin-walled, and inamyloid basidiospores; cystidia that are present or absent; and sarcodimitic tramal tissues (Singer 1951; Norvell et al. 1994). Species of Gerronema are widespread in subtropical to tropical regions but are also rarely distributed in temperate zones (Singer 1951, 1970; Norvell et al. 1994). Studies of Gerronema during the past 70 years have focused on species distributed in South America and Asia, with 11 new species and six new combinations recognized from Argentina, the USA, Brazil, Japan, India and China (Singer 1951, 1959; Liu 1995; Takahashi 2000; Desjardin et al. 2005; Latha et al. 2018; Liu et al. 2019). In contrast, few investigations of Gerronema taxa in Europe, Australia, and Africa have been conducted, and only one new species and two new combinations have been reported from these regions (Bañares et al. 2006; Degreef and Ndong 2007; Cooper 2014).

Only three Gerronema species, including two new to the genus, have previously been recognized in China (Liu 1995; Dai et al. 2010; Liu et al. 2019). In recent years, progress has been achieved in clarifying the status of mycenoid and omphalinoid fungi in China, including a new taxon reported from Zhejiang Province, China, namely, Leucoinocybe lishuiensis Q. Na, H. Zeng & Y.P. Ge, which is sister to Gerronema (Na and Bau 2018, 2019a, 2019b; Ge et al. 2021; Na et al. 2021). During our ongoing research on omphalinoid fungi, we discovered three new species belonging to Gerronema in subtropical China. These species are formally described here as G. baishanzuense Q. Na, H. Zeng & Y.P. Ge, G. microcarpum Q. Na, H. Zeng & Y.P. Ge, and G. zhujian Q. Na, H. Zeng & Y.P. Ge. In addition, we have determined that G. nemorale Har. Takah., which has not previously been recorded in China, is widely distributed in the country. We accordingly present a morphological description of the new and newly recorded species, and we also provide a key for identification of the seven species of Gerronema currently known from China.

Materials and methods

Sample collection and morphological description

Specimens were collected in Anhui, Fujian, Jilin, and Zhejiang provinces, China, from June 2019 to August 2021. Basidiomata were photographed in their natural habitats with a Canon 90D digital camera and then dried on allochroic silica gel. Fresh fruiting bodies were recorded in the field to identify macroscopic characters. In our descriptions, color codes and notations follow Kornerup & Wanscher (Kornerup and Wanscher 1978). Microscopic features were conducted on dried specimens mounted in 5% KOH and stained with Congo red when necessary. Melzer’s reagent was used to test whether spores and tissues were amyloid (Horak 2005). Twenty mature basidiospores from each basidiocarp were measured, the notation [a/b/c] used at the beginning of each basidiospore description indicates that a basidiospores from b basidiocarps of c specimens were measured. The dimensions of basidiospores and Q values are presented as (d) e–f–g (h) × (i) j–k–l (m), where d is the minimum length, eg represents the range of at least 90% of values, f is the average length, and h is the maximum length; width (im) is expressed in the same manner. In addition, Q is the length: width ratio of a spore, and Q ± SD is the average Q of all basidiospores ± the sample standard deviation (Ge et al. 2021; Liu et al. 2021; Na et al. 2021). Hyphae of the pileipellis and stipitipellis and a total of 20 basidia, cheilocystidia, and caulocystidia were measured from each collection. Author abbreviations follow those used in Index Fungorum (https://www.indexfungorum.org). Voucher specimens have been deposited in the Fungarium of the Fujian Academy of Agricultural Sciences (FFAAS), China.

Phylogenetic reconstruction

Genomic DNA was extracted from dried specimens using a NuClean Plant Genomic DNA kit (Kangwei Century Biotechnology Co., Beijing, China). The internal transcribed spacer (ITS) region and the nuclear large subunit (nLSU) of ribosomal DNA were respectively amplified with primer pairs ITS1/ITS4 and LR0R/LR7 (White et al. 1990; Hopple and Vilgalys 1999). The PCR thermocycling protocol (for both ITS and nLSU) was the same as reported in Ge et al. (2021). A dataset comprising sequences from 38 accessions of seven genera of Porotheleaceae and Mycena purpureofusca as an outgroup was compiled for phylogenetic analysis. All newly generated sequences and those downloaded from GenBank are shown in Table 1. The sequences used in this study were aligned and adjusted manually using BioEdit 7.0.4.1 and Clustal X (Thompson et al. 1997; Hall 1999). In the alignment, gaps were treated as missing data. The alignment was deposited in TreeBase (submission ID: 29143; study accession URL: http://purl.org/phylo/treebase/phylows/study/TB2:S29143). The best model of nucleotide evolution for the ITS and nLSU data was identified using Modeltest 2.3 (Nylander 2004). The optimized sequence dataset was analyzed using Bayesian inference (BI) and maximum likelihood (ML) methods in MrBayes 3.2.6 and raxmlGUI 1.5b1, respectively (Ronquist and Huelsenbeck 2003; Stamatakis 2006). The BI analysis was performed for 2 million generations, with trees sampled every 100 generations. The sampled trees were subsequently summarized by using the “sump” and “sumt” commands after discarding the first 25% of iterations as burn-in. For the ML analysis, default parameters in RAxML were used with 1,000 bootstrap replicates. Phylogenetic trees were visualized with Figtree 1.4.3.

Table 1.

Sequenced specimens used in phylogenetic analysis. New and newly recorded species are marked in bold.

No. Taxa Voucher Locality ITS Sequences ID nLSU Sequences ID Reference
1 Chrysomycena perplexa MCVE:30184 Italy MN496427 NG071251 Vizzini et al. 2019
2 Clitocybula abundans STU:SMNS-B-FU-2017/00898 not indicated MF627833 from GenBank
3 C. familia PRM 921866 Czech JF730327 JF730320 Antonín et al. 2011
4 C. familia BRNM 736053 Slovakia JF730328 JF730323 Antonín et al. 2011
5 C. familia 2319-QFB-25741 not indicated KM406970 from GenBank
6 C. familia STU:SMNS-B-FU-2017/00926 not indicated MF627834 from GenBank
7 C. familia NAMA 2017-349 not indicated MH979253 from GenBank
8 C. flavoaurantia D Italy HM191743 Malysheva and Morozova 2011
9 C. flavoaurantia GDOR Italy HM191744 Malysheva and Morozova 2011
10 C. flavoaurantia LE 262757 Russia HM191745 Malysheva and Morozova 2011
11 C. lacerata LE 6639 Russia HM191746 Malysheva and Morozova 2011
12 C. lacerata LE 262744 Russia HM191747 Malysheva and Morozova 2011
13 C. lacerata LE 262743 Russia HM191748 Malysheva and Morozova 2011
14 C. lignicola BPI M-20.989 Russia HM191735 Malysheva and Morozova 2011
15 C. lignicola BPI M-20.825 Russia HM191736 Malysheva and Morozova 2011
16 C. lignicola LE253926 Russia HM191741 Malysheva and Morozova 2011
17 C. lignicola LE262737 Russia HM191742 Malysheva and Morozova 2011
18 C. oculus AFTOL-ID 1554 USA DQ192178 Matheny et al. 2006
19 C. oculus 3512 not indicated KM406971 from GenBank
20 C. oculus BIOUG24046-B03 Canada KT695321 Telfer et al. 2015
21 C. oculus WU 20008 Austria LT854017 LT854017 Antonín et al. 2019
22 C. oculus S.D. Russell iNaturalist # 8591258 India MN906164 from GenBank
23 C. oculus S.D. Russell iNaturalist # 8606755 India MN906165 from GenBank
24 Gerronema atrialbum AFTOL-ID 1529 USA DQ192179 DQ192179 Matheny et al. 2006
25 G. baishanzuense FFAAS0359 Holotype China OL985962 OL985984 This study
26 G. baishanzuense FFAAS0360 China OL985963 This study
27 G. baishanzuense FFAAS0361 China OL985964 OL985985 This study
28 G. baishanzuense FFAAS0362 China OL985965 OL985986 This study
29 G. baishanzuense FFAAS0363 China OL985966 OL985987 This study
30 G. baishanzuense FFAAS0366 China OL985967 OL985988 This study
31 G. indigoticum HMJAU 47636 China MK693727 MK693732 Liu et al. 2019
32 G. indigoticum HMJAU 47942 China MK693728 MK693733 Liu et al. 2019
33 G. indigoticum HMJAU 47943 China MK693729 MK693734 Liu et al. 2019
34 G. keralense CAL 1666 India MH156555 NG_064531 Latha et al. 2018
35 G. kuruvense CAL 1665 India NG_159831 NG_064530 Latha et al. 2018
36 G. microcarpum FFAAS0365 China OL985989 from GenBank
37 G. microcarpum FFAAS0371 China OL985968 OL985990 from GenBank
38 G. microcarpum FFAAS0372 China OL985969 OL985991 from GenBank
39 G. microcarpum FFAAS0373 Holotype China OL985970 OL985992 from GenBank
40 G. microcarpum FFAAS0374 China OL985971 from GenBank
41 G. microcarpum FFAAS0375 China OL985972 OL985993 from GenBank
42 G. nemorale KACC 43599 Korea EU883592 This study
43 G. nemorale KACC 43600 Korea EU883593 This study
44 G. nemorale not indicated Korea EU883594 This study
45 G. nemorale FA249 Pakistan MN744686 This study
46 G. nemorale FA236 Pakistan MN744687 This study
47 G. nemorale FA239 Pakistan MN744688 This study
48 G. nemorale FFAAS0377 China OL985976 OL985997 This study
49 G. nemorale FFAAS0379 China OL985977 OL985998 This study
50 G. nemorale FFAAS0382 China OL985978 OL985999 This study
51 G. nemorale FFAAS0384 China OL985979 OL986000 This study
52 G. nemorale FFAAS0388 China OL985980 OL986001 This study
53 G. nemorale FFAAS0389 China OL985981 OL986002 This study
54 G. nemorale FFAAS0392 China OL985982 OL986003 This study
55 G. nemorale FFAAS0410 China OL985983 OL986004 This study
56 G. strombodes DJL05NC72 USA EU623639 Hughes et al. 2007
57 G. strombodes TFB12519/TENN60718 USA EU623640 Hughes et al. 2007
58 G. strombodes TFB12783/TENN61350 USA EU623641 Hughes et al. 2007
59 G. strombodes TFB11947 clone C2 USA KY242503 Hughes et al. 2007
60 G. strombodes TFB11947 clone C3 USA KY242504 Hughes et al. 2007
61 G. strombodes TFB11947 clone C5 USA KY242506 Hughes et al. 2007
62 G. strombodes TFB14234 USA KY242507 Hughes et al. 2007
63 G. strombodes TFB14514 USA KY242509 Hughes et al. 2007
64 G. strombodes TFB11947 USA KY271083 from GenBank
65 G. subclavatum Redhead 5175, DAOM not indicated U66434 Lutzoni 1997
66 G. subclavatum FLAS-F-60986 USA MH016932 from GenBank
67 G. subclavatum FLAS-F-61518 USA MH211945 from GenBank
68 G. subclavatum Smith-2018 USA MK573888 Direct Submission
69 G. subclavatum Mushroom Observer # 243440 USA MK607510 Direct Submission
70 G. subclavatum iNaturalist # 8545787 India MN906021 from GenBank
71 G. subclavatum S.D. Russell MycoMap # 6854 India MN906138 from GenBank
72 G. viridilucens SP307883 (SP) Brazil EF514207 Desjardin et al. 2005
73 G. waikanaense PDD:87667 New Zealand JQ694117 from GenBank
74 G. wildpretii BRNM 788347 Madeira LT854045 LT854043 Antonín et al. 2019
75 G. xanthophyllum PRM 924657 Czech LT854023 LT854023 Antonín et al. 2019
76 G. zhujian FFAAS0364 China OL985973 OL985994 This study
77 G. zhujian FFAAS0370 China OL985974 OL985995 This study
78 G. zhujian FFAAS0376 Holotype China OL985975 OL985996 This study
79 Hydropus fuliginarius DAOM196062 USA AF261368 Moncalvo et al. 2002
80 H. marginellus AFTOL-ID 1720 Czech DQ490627 DQ457674 Matheny et al. 2006
81 H. marginellus OSC 112834 USA EU669314 EU852808 from GenBank
82 Leucoinocybe lishuiensis FFAAS 0111 China MW424488 MW424492 Na et al. 2021
83 L. lishuiensis FFAAS 0112 China MW424489 MW424493 Na et al. 2021
84 L. lishuiensis FFAAS 0113 China MW424490 MW424494 Na et al. 2021
85 L. lishuiensis FFAAS 0115 China MW424491 MW424495 Na et al. 2021
86 L. sp. KA12-0435 South Korea KR673482 Kim et al. 2015
87 L. sulcata CAL 1246 (HOLOTYPE) India KR029720 KR029721 Latha et al. 2015
88 L. taniae BCN-SCM B-4064 Italy LT854057 LT854028 Antonín et al. 2019
89 Megacollybia clitocyboidea TFB11884/TENN60766 USA EU623658 Hughes et al. 2007
90 M. clitocyboidea TENN62231 USA EU623664 Hughes et al. 2007
91 M. clitocyboidea TENN62230 clone c4 USA EU623673 Hughes et al. 2007
92 M. clitocyboidea TENN62230 clone c5 USA EU623674 Hughes et al. 2007
93 M. fallax MICH 45002 USA EU623714 Hughes et al. 2007
94 M. fallax TFB11561/TENN59447 USA EU623723 Hughes et al. 2007
95 M. fallax DAOM208710 USA EU623724 Hughes et al. 2007
96 M. fallax Mushroom Observer 291302 USA MN176984 Direct Submission
97 M. fallax Mushroom Observer 286893 USA MT437075 Direct Submission
98 M. marginata TENN60752 USA EU623685 Hughes et al. 2007
99 M. marginata HR 91607 Czech LT854051 Antonín et al. 2019
100 M. platyphylla TFB11572/TENN59523 USA EU623712 Hughes et al. 2007
101 M. platyphylla LE 256-2004 USA EU623713 Hughes et al. 2007
102 M. platyphylla 10164 Italy JF908499 Osmundson et al. 2013
103 M. platyphylla BRNM 737654 Czech LT854048 LT854036 Antonín et al. 2019
104 M. platyphylla LE-BIN 3863 Russia MG734826 from GenBank
105 M. rodmani BHS2009-06 USA GQ397989 from GenBank
106 M. rodmani PUL F27039 USA MW448576 from GenBank
107 M. subfurfuracea TFB11075/TENN59558 clone c3 USA EU623744 Hughes et al. 2007
108 M. subfurfuracea TFB11075/TENN59558 clone c8 USA EU623745 Hughes et al. 2007
109 M. texensis DPL7405/TENN62058 clone c1 USA EU623725 Hughes et al. 2007
110 M. texensis DPL7405/TENN62058 clone c2 USA EU623726 Hughes et al. 2007
111 M. texensis FLAS-F-61511 USA MH211940 from GenBank
112 Mycena purpureofusca HMJAU 43554 China MG654740 Na and Bau 2018
113 Mycena purpureofusca HMJAU 43624 China MG654741 Na and Bau 2018
114 Mycena purpureofusca HMJAU 43640 China MG654742 Na and Bau 2018
115 Porotheleum fimbriatum Dai 12276 China KX081137 KX161656 from GenBank
116 P. fimbriatum Dai 12289 China KX081138 KX161654 from GenBank
117 P. fimbriatum CLZhao 1120 China MH114870 from GenBank
118 P. fimbriatum CLZhao 2368 China MH114871 from GenBank
119 P. fimbriatum SWFC 006350 China MK894078 from GenBank
120 P. fimbriatum SWFC 006399 China MK894079 from GenBank
121 Trogia benghalensis CUH AM031 India KU647630 Dutta et al. 2017
122 T. benghalensis CUH AM122 India MF967246 Dutta et al. 2017
123 T. infundibuliformis KUN_HKAS63661 China JQ031775 JQ031780 Yang et al. 2012
124 T. infundibuliformis KUN_HKAS56709 China JQ031776 JQ031781 Yang et al. 2012
125 T. infundibuliformis NW1487 Thailand MW504969 Direct Submission
126 T. venenata KUN_HKAS54710 China JQ031772 JQ031778 Yang et al. 2012
127 T. venenata KUN_HKAS56679 China JQ031773 JQ031779 Yang et al. 2012
128 T. venenata TC2-28 China KT968080 Mi et al. 2016
129 T. venenata CLZhao 4141 China MK268886 from GenBank

Results

Phylogenetic analysis

The concatenated dataset of 127 ITS and 50 nLSU sequences from 38 taxa of eight genera in Porotheleaceae, with the addition of one Mycena species as an outgroup, comprised 1,527 sites. Sequences retrieved from GenBank and those obtained in this study are listed in Table 1.

BI and ML phylogenetic analyses of the concatenated dataset were performed under the optimal evolutionary model selected for both ITS and nLSU partitions, GTR + I + G (lset nst = 6, rates = gamma, and prset statefreqpr = dirichlet [1,1,1,1]). Because the BI and ML phylogenetic reconstructions were consistent in topology, only the ML tree is shown in Fig. 1.

Figure 1. 

Maximum Likelihood and Bayesian tree concatenated ITS + nLSU dataset. In the generated trees, ML bootstrap support values greater than 75% and Bayesian posterior probabilities (BPP) greater than 0.90 are shown for relevant branch nodes (BS ≥ 75%, BPP ≥ 0.90). The tree is rooted with Mycena purpureofusca. The new species, Gerronema baishanzuense, G. microcarpum, and G. zhujian are marked by red. The newly discovered species, G. nemorale Har. Takah. is marked by green.

In the phylogenetic tree shown in Fig. 1, 17 major clades are evident. Chrysomycena Vizzini, Picillo, Perrone & Dovana, Clitocybula, Hydropus, Leucoinocybe Singer ex Antonín, Borovička, Holec & Kolařík, Megacollybia, Porotheleum Fr., and Trogia form monophyletic groups, whereas Gerronema is polyphyletic (Vizzini et al. 2019). In the analysis of Vizzini et al. (2019), Gerronema was resolved into eight clades; in our tree, this number is increased to 10, including 13 species, which we have designated as Gerronema clades 1 to 10.

Each individual Gerronema clade (e.g., Gerronema 1, Gerronema 2, etc.) is sister to some subset of Porotheleaceae genera, all with high statistical support (ML bootstrap support [BS] = 100%, Bayesian posterior probability [BPP] = 1.00). Samples of the three new species and the newly recorded species are placed in Gerronema 1, Gerronema 2, Gerronema 6, and Gerronema 7 clades, where they constitute monophyletic lineages, each with high statistical support (G. baishanzuense, BS = 100%, BPP = 1.00; G. microcarpum, BS = 100%, BPP = 1.00; G. zhujian, BS = 100%, BPP = 1.00; G. nemorale, BS = 98%, BPP = 0.99; Fig. 1). The two new species G. baishanzuense and G. zhujian form a monophyletic lineage that is sister to a group comprising Gerronema 5 and Gerronema 8 clades, the latter consisting of G. strombodes (Berk. & Mont.) Singer and G. kuruvense K.P.D. Latha & Manim. Gerronema microcarpum, which is well supported as a species, is placed along with G. keralense K.P.D. Latha & Manim., a new species recently reported from India, in the Gerronema 1 clade (Latha et al. 2018). In contrast, G. nemorale is polyphyletic, with accessions of this species and G. subclavatum forming an unresolved lineage in the Gerronema 2 clade that are difficult to distinguish genetically.

The weakly supported Gerronema 3 clade consists of two species: G. xanthophyllum (Bres.) Norvell, Redhead & Ammirati and G. waikanaense (G. Stev.) J.A. Cooper, collected from the Czech Republic and New Zealand, respectively. Finally, Gerronema clades 5 to 10 comprise a single species each.

Taxonomy

Gerronema baishanzuense Q. Na, H. Zeng & Y.P. Ge, sp. nov.

MycoBank No: 842308
Figs 2, 3, 4

Diagnosis

Pileus dark brown at center, covered with dark brown fibrillose or pubescent. Stipe densely pruinose when young. Cheilocystidia present. Pileus trama with visible dark brown hyphae and coarse excrescences.

Figure 2. 

Fresh basidiomata of Gerronema baishanzuense Q. Na, H. Zeng & Y.P. Ge a–e FFAAS0359 (Holotype) f–g FFAAS0360 h–i FFAAS0361 j–k FFAAS0362 l–m FFAAS0363 n–o FFAAS0366. Scale bars: 10 mm (a–o). Photographs a–e by Qin Na; f–g by Junqing Yan h–i by Liangliang Qi j–o by Yupeng Ge.

Holotype

China. Zhejiang Province, Lishui City, Qingyuan County, Baishanzu, 8 Jul 2020, Qin Na, Yupeng Ge, Yaping Hu, Hui Zeng, and Zewei Liu, FFAAS0359 (collection no. MY0246).

Figure 3. 

Microscopic features of Gerronema baishanzuense Q. Na, H. Zeng & Y.P. Ge. (FFAAS0359, Holotype) a–e basidiospores f basidia g–i cheilocystidia j lamellar trama k pileipellis l stipitipellis and caulocystidia. Scale bars: 5 μm (a–e); 10 μm (f–l).

Etymology

Refers to the type locality.

Description

Pileus 3.0–25.5 mm in diam., hemispherical when young, becoming applanate and slightly concave at center with age, deeply infundibuliform when old, with uplifted margin, dark brown all over when young (2F8), dark brown at center and fading to light yellowish brown (2D4) towards the margin at maturity, margin light yellowish white (2A2), translucent–striate, sulcate, surface dry, with appressed dark brown (2F8) fibrillose or pubescent, margin glabrescent and brown (2F8), fibrillose or pubescent at the center with age. Context thin and fragile, yellowish white (2A2). Lamellae subdecurrent to decurrent, ascending, cream-white (3A2) to light yellowish white (2A2), faces concolorous with the sides. Stipe slender, 4.5–26.0 × 0.5–2.0 mm, hollow, cylindrical, central, straight, light whitish yellow (4A2), base yellow-brown (4D8) when old, densely pruinose on the entire surface when young, almost glabrous when old, slightly broadened at the base. Odor and taste inconspicuous.

Figure 4. 

Morphological features of Gerronema baishanzuense Q. Na, H. Zeng & Y.P. Ge. (FFAAS0359, Holotype) a basidiomata b basidia c basidiospores d cheilocystidia e stipitipellis and caulocystidia f pileipellis. Scale bars: 10 mm (a); 10 μm (b–f). Drawing by Qin Na and Yupeng Ge.

Basidiospores [140/7/6] (6.6) 7.5–8.4–9.3 (9.8) × (4.0) 4.4–4.9–5.4 (5.6) μm [Q = 1.65–1.74, Q = 1.72 ± 0.015] [holotype [40/2/1] (7.6) 7.9–8.6–9.5 (9.8) × (4.3) 4.5–4.9–5.5 (5.6) μm, Q = 1.72–1.74, Q = 1.74 ± 0.031], long ellipsoid, hyaline, guttulate, thin-walled, inamyloid. Basidia 31–45 × 6–9 μm, hyaline, clavate, 4-spored. Cheilocystidia 30–48 × 8–14 μm, clavate with swollen apex, or subfusiform, hyaline, thin-walled. Pleurocystidia not seen. Lamellar trama subregular; hyphae 2–10 μm wide, thin-walled, hyaline, inamyloid. Pileus trama subregular, sarcodimitic, sometimes with dark brown (4F8) hyphae. Pileipellis a cutis, hyphae 2–6 μm wide, light yellow (2B2) to yellow (2B4), occasionally with coarse excrescences; terminal elements utriform, clavate, sometimes with sparse coarse excrescences, 25–56 × 6–10 μm, light yellowish brown (2C4) to yellowish brown (2C6) pigment in KOH; true pileocystidia absent. Hyphae of the stipitipellis 2–7 μm wide, hyaline, smooth; caulocystidia cylindrical or clavate, 39–70 × 5–14 μm, hyaline, thin-walled. All tissues nonreactive in iodine. Clamps present in all tissues.

Habit and habitat

Solitary to scattered on rotten wood, branches, and twigs in mixed forests of Picea, Pinus, Populus, Quercus, etc. Subtropical monsoon climate or subtropical humid climate.

Other specimens examined

Anhui Province, Chizhou City, Shitai County, Dayan Village, Guniujiang National Natural Reserve, 31 Aug 2019, Qin Na, Yupeng Ge, Hui Zeng, Liangliang Qi, and Junqing Yan, FFAAS0366 (collection no. MY0260); Zhejiang Province, Lishui City, Qingyuan County, Baishanzu, 24 May 2020, Qin Na, Yupeng Ge, Yaping Hu, Hui Zeng, and Zewei Liu, FFAAS0360 (collection no. MY0247), FFAAS0362 (collection no. MY0250); Zhejiang Province, Lishui City, Qingyuan County, Jushui Village, 27 May 2020, Qin Na, Yupeng Ge, Yaping Hu, Hui Zeng, and Zewei Liu, FFAAS0361 (collection no. MY0249), Longquan City, Longquan Mountain, 11 Jul 2020, Qin Na, Yupeng Ge, Yaping Hu, Hui Zeng, and Zewei Liu, FFAAS0363 (collection no. MY0251).

Remarks

Gerronema baishanzuense is considered to be a distinct species of Gerronema on account of its deeply infundibuliform pileus, decurrent lamellae, smooth and long ellipsoid basidiospores, sarcodimitic tramal tissues, cylindrical or clavate caulocystidia, and a lignicolous habitat (Singer 1986; Redhead 1986; Norvell et al. 1994). Four species with a yellow pileus have been recorded: G. keralense, G. kuruvense, G. nemorale, and G. strombodes (Singer 1970; Takashi 2009; Antonín et al. 2011; Latha et al. 2018; Takahashi 2000). Gerronema nemorale, originally described from Japan and later reported from the Republic of Korea, has the most morphological similarities to G. baishanzuense; however, the former differs in having a smaller pileus (< 20 mm in diameter) but a longer stipe (up to 40 mm), terminal elements less than 37 μm long, and much smaller caulocystidia (Takahashi 2000; Antonín et al. 2008). In contrast to G. baishanzuense, two new species recently reported from the Indian state of Kerala, G. keralense and G. kuruvense, are easily mistaken for the new species (Latha et al. 2018). However, the pileus of G. keralense lacks dark brown fibrillose or pubescent, has smaller and slightly thick-walled cheilocystidia, and the hyphae of its stipitipellis and caulocystidia are both thin- to thick-walled (Latha et al. 2018). Gerronema kuruvense is always distinctly yellow, has small basidiomata (pileus < 11 mm in diameter) and true pileocystidia, and lacks cheilocystidia (Latha et al. 2018). Finally, G. strombodes, distributed in North America and Asia, differs from G. baishanzuense in having larger basidiomata, a white to grayish white pileus (up to 80 mm wide), smooth pileipellis hyphae, and the absence of hymenial cystidia (Singer 1970; Antonín et al. 2008; Kim et al. 2014). G. citrinum (Corner) Pegler (Pegler 1983) and G. tenue Dennis (Dennis 1961), are allied with G. baishanzuense, but their lamellae edges without cheilocystidia. Moreover, G. citrinum has a relatively larger pileus (20–30 mm in diam.) and smaller basidiospores (6–7.5 × 3.5–4 μm), and G. tenue differs in having a citrine yellow pileus and an insititious stipe (Dennis 1961; Pegler 1983). G. hungo (Henn.) Degreef & Eyi, reported by Degreef and Ndong (2007) as a new combination, differs in yellowish orange to brownish orange pileus, ellipsoid basidiospores, and absent cheilocystidia.

Gerronema microcarpum Q. Na, H. Zeng & Y.P. Ge, sp. nov.

MycoBank No: 842309
Figs 5, 6, 7

Diagnosis

Basidiomata distinctly small. A pileus a bit slimy when moist. Stipe light yellow, base turning to light brown with age. Cheilocystidia common in clavate with rounded apex, rarely fusiform. Pileipellis occasionally with coarse excrescences.

Figure 5. 

Fresh basidiomata of Gerronema microcarpum Q. Na, H. Zeng & Y.P. Ge. a FFAAS0365 b FFAAS0372 c–d FFAAS0375 e FFAAS0373 (Holotype) f–g FFAAS0374 h–i FFAAS0371. Scale bars: 10 mm (a–i). Photographs a, e–i by Yupeng Ge; b by Junqing Yan; c–d by Qin Na.

Holotype

China. Zhejiang Province, Lishui City, Qingtian County, Shigu Lake, 6 Aug 2021, Qin Na, Yupeng Ge, Junqing Yan, Zewei Liu, and Yulan Sun, FFAAS0373 (collection no. MY0526).

Figure 6. 

Microscopic features of Gerronema microcarpum Q. Na, H. Zeng & Y.P. Ge. (FFAAS0373, Holotype) a–e basidiospores f basidia g–i cheilocystidia j lamellar trama k pileipellis l stipitipellis and caulocystidia. Scale bars: 5 μm (a–e); 10 μm (f–l).

Etymology

Refers to the small basidiomata.

Description

Pileus 1.5–9.0 mm in diam., at first convex, later applanate in the marginal zone, infundibuliform or deeply umbilicate in the center when old, grayish yellow (2B2) to shallow yellowish brown (2C4), shallowly sulcate, translucent–striate, smooth, a bit slimy when moist, but not hygrophanous. Context yellowish white (2A2), thin. Lamellae close to moderately close, shortly decurrent when young, whitish yellow (1A2), decurrent to deeply decurrent when old, concolorous with the sides. Stipe 5.0–18.0 × 1.0–2.0 mm, hollow or soon becoming hollow, generally central, equal or with slightly broader base, light yellow (2A2), becoming light brown (5C6) towards the base, pruinose, glabrescent when old, base covered with a few white fibrils. Odor and taste indistinctive.

Figure 7. 

Morphological features of Gerronema microcarpum Q. Na, H. Zeng & Y.P. Ge. (FFAAS0373, Holotype) a basidiomata b basidia c basidiospores d cheilocystidia e stipitipellis and caulocystidia f pileipellis. Scale bars: 10 mm (a); 10 μm (b, d–f); 5 μm (c). Drawing by Qin Na and Yupeng Ge.

Basidiospores [140/7/6] (6.1) 6.3–6.8–7.2 (7.5) × (3.3) 3.5–3.8–4.1 (4.3) μm [Q = 1.64–1.95, Q = 1.80 ± 0.059] [holotype [40/2/1] (6.1) 6.2–6.7–7.3 (7.5) × 3.4–3.7–4.1 (4.3) μm, Q = 1.64–1.95, Q = 1.81 ± 0.066], narrowly ellipsoid to cylindrical, hyaline in water and 5% KOH, inamyloid, smooth. Basidia 25–33 × 6–8 μm, 4-spored, clavate, hyaline. Cheilocystidia common in clavate with rounded apex, 31–35 × 5–8 μm, rarely fusiform, thin-walled and hyaline. Pleurocystidia not seen. Lamellar trama subregular; hyphae 2–5 μm wide, thin-walled, hyaline, inamyloid. Pileus trama subregular, sarcodimitic. Pileipellis a cutis, hyphae 3–6 μm wide, light yellow (2B2); terminal elements clavate, utriform, occasionally with coarse excrescences, 19–43 × 4–6 μm, light yellowish brown (2C4) to yellowish brown (2D4) pigment in KOH; true pileocystidia absent. Hyphae of the stipitipellis 2–6 μm wide, hyaline, smooth; caulocystidia long cylindrical or clavate, 26–65 × 4–9 μm, hyaline, thin-walled. All tissues nonreactive in iodine. Clamps present in all tissues.

Habit and habitat

Scattered on rotten wood and twigs in mixed evergreenbroadleaf forests consisting of species of Fagaceae, Lauraceae, Theaceae, Ericaceae, Symplocaceae, Pinaceae, etc. Subtropical monsoon climate or subtropical humid climate.

Other specimens examined

Anhui Province, Chizhou City, Shitai County, Dayan Village, Guniujiang National Natural Reserve, 31 Aug 2019, Qin Na, Yupeng Ge, Hui Zeng, Liangliang Qi, and Junqing Yan, FFAAS0365 (collection no. MY0259); Fujian Province, Nanping City, Wuyi Mountain, 25 Jul 2020, Qin Na, Yupeng Ge, Yaping Hu, Hui Zeng, and Zewei Liu, FFAAS0375 (collection no. MY0544); Zhejiang Province, Hangzhou City, Tianmu Mountain, 30 Jul 2021, Qin Na, Yupeng Ge, Zewei Liu, and Yulan Sun, FFAAS0371 (collection no. MY0424); Lishui City, Liandu District, Baiyun National Forest Park, 2 Aug 2021, Qin Na, Yupeng Ge, Zewei Liu, and Yulan Sun, FFAAS0372 (collection no. MY0478), Qingtian County, Shigu Lake, 6 Aug 2021, Qin Na, Yupeng Ge, Junqing Yan, Zewei Liu, and Yulan Sun, FFAAS0374 (collection no. MY0527).

Remarks

Characteristics such as tiny omphalinoid basidiomata, decurrent lamellae, inamyloid and narrowly ellipsoid to cylindrical basidiospores, sarcodimitic tramal tissues, a pileipellis with pigmented terminal elements, and long cylindrical or clavate caulocystidia support the placement of this species in Gerronema (Singer 1970, 1986; Norvell et al. 1994). Because of its small basidiomata, decurrent lamellae, and subregular pileus trama, G. kuruvense is difficult to distinguish from G. microcarpum, but its pileus is orange yellow all over, no cheilocystidia or pleurocystidia are present, and its pileocystidia and caulocystidia are somewhat thick-walled (Latha et al. 2018). Gerronema nemorale has certain morphological similarities to G. microcarpum, namely, the presence of tiny yellowish basidiomata, decurrent lamellae, and cylindrical basidiospores (Antonín et al. 2008, 2011; Takashi 2009). However, G. nemorale differs in having a pileus with an olive tint, a longer stipe with conspicuous white mycelioid bristles, and larger terminal elements of the pileipellis (up to 150 μm) (Antonín et al. 2008, 2011; Takashi 2009). Compared with G. microcarpum, G. subchrysophyllum (Murrill) Singer has an olive-umber pileus fading to grayish when old, larger and ellipsoid basidiospores (4.3–8.5 × 2.5–6.3 μm), and sometimes basidiole-like cheilocystidia (Singer 1970). Gerronema keralense and G. strombodes are easily mistaken for G. microcarpum, but both the two closely related species are distinguishable by their absence of cheilocystidia or their partially thick-walled pileipellis and stipitipellis (Singer 1970; Antonín et al. 2008; Latha et al. 2018; Kim et al. 2014).

Gerronema zhujian Q. Na, H. Zeng & Y.P. Ge, sp. nov.

MycoBank No: 842310
Figs 8, 9, 10

Diagnosis

Pileus fuscous and densely covered with tiny, deep brown fur or scales, distinctly radially striped with darkened lines. Stipe white, upper part slight brown when old. Cheilocystidia present. Pileipellis without coarse excrescences.

Figure 8. 

Fresh basidiomata of Gerronema zhujian Q. Na, H. Zeng & Y.P. Ge. a–b FFAAS0364 c–d FFAAS0376 (Holotype) e–f FFAAS0370. Scale bars: 10 mm (a–f). Photographs a–b, e–f by Liangliang Qi c–d by Junqing Yan.

Holotype

China. Fujian Province, Nanping City, Wuyi Mountain, 25 Jul. 2020, Qin Na, Yupeng Ge, Yaping Hu, Hui Zeng, and Zewei Liu, FFAAS0376 (collection no. MY0553).

Figure 9. 

Microscopic features of Gerronema zhujian Q. Na, H. Zeng & Y.P. Ge. (FFAAS0376, Holotype) a–e basidiospores f basidia g–i cheilocystidia j lamellar trama k pileipellis l stipitipellis and caulocystidia. Scale bars: 5 μm (a–e); 10 μm (f–l).

Etymology

The name refers to the centrally depressed, umbilicate basidiocarps, which resemble an eye or a loudspeaker; zhujian is a mythical one-eyed Chinese creature who is usually very noisy, like a walking loudspeaker.

Figure 10. 

Morphological features of Gerronema zhujian Q. Na, H. Zeng & Y.P. Ge. (FFAAS0376, Holotype) a basidiomata b basidia c basidiospores d cheilocystidia e stipitipellis and caulocystidia f pileipellis. Scale bars: 10 mm (a); 10 μm (b–f). Drawing by Qin Na and Yupeng Ge.

Description

Pileus 8.6–18.5 mm in diam., convex to broadly convex, papillate, applanate and centrally depressed, subumbilicate to umbilicate with age, pellucid-striate to rugulo-striate, or sulcate, always ± distinctly radially striped with darkened lines, fuliginous-fuscous (2F8) or fuscous (4F8) at center when young, grayish white (3B1) towards the margin, fading to brown (3F8) at the center, yellowish-brown (4E8) towards the margin, densely covered with tiny, deep brown (4F4) fur or scales, slightly sparse with age, with a slightly involuted margin. Context white, thin, tough. Lamellae subdecurrent to decurrent, moderately broad, pure white to yellowish-white (4A2), edges concolorous with the sides. Stipe 19.0–25.0 × 1.0–1.5 mm, central, cylindrical, almost equal above, white, slight brown (8D3–8D4) in upper part when old, fibrous, hollow, pruinose, base slightly swollen with tiny, white fine hairs. Odorless, taste mild.

Basidiospores [80/4/3] (6.3) 6.7–7.4–8.0 (8.5) × (3.2) 3.7–4.1–4.6 (4.8) μm [Q = 1.64–2.07, Q = 1.81 ± 0.076] [holotype [40/2/1] (6.3) 6.6–7.4–7.9 (8.3) × (3.2) 3.7–4.0–4.5 (4.6) μm, Q = 1.69–2.07, Q = 1.82 ± 0.087], narrowly ellipsoid to cylindrical, hyaline, guttulate, thin-walled, inamyloid. Basidia 28–40 × 6–9 μm, hyaline, clavate, 4-spored. Cheilocystidia 29–46 × 7–13 μm, subfusiform, clavate, apex usually swollen, hyaline. Pleurocystidia absent. Lamellar trama subregular; hyphae 3–8 μm wide, thin-walled, hyaline, inamyloid. Pileus trama subregular, sarcodimitic. Pileipellis hyphae 3–6 μm wide, a cutis, light yellow (2B2); terminal elements utriform or clavate, 25–49 × 6–9 μm, light yellowish brown (2C4) to yellowish brown (2C6) pigmented, especially in the apex; true pileocystidia absent. Hyphae of the stipitipellis 2–8 μm wide, hyaline, smooth; caulocystidia long cylindrical, sometimes with rounded apex, 27–47 × 4–8 μm, hyaline, thin-walled. All tissues nonreactive in iodine. Clamps present in all tissues.

Habit and habitat

Solitary to scattered on rotten wood, branches, and twigs in Theaceae, Fagaceae, Symplocaceae, Lauraceae, Aquifoliaceae, Ericaceae, and Pinaceae mixed forests. Subtropical monsoon climate, subtropical humid climate or subtropical maritime monsoon climate.

Other specimens examined

Anhui Province, Chizhou City, Shitai County, Dayan Village, Guniujiang National Natural Reserve, 26 Jul 2019, Qin Na, Yupeng Ge, Hui Zeng, Junqing Yan, and Liangliang Qi, FFAAS0364 (collection no. MY0256); Fujian Province, Sanming City, Mingxi County, Junzifeng National Natural Reserve, 23 Jun 2021, Qin Na, Yupeng Ge, Liangliang Qi, and Binrong Ke, FFAAS0370 (collection no. MY0296).

Remarks

Gerronema zhujian is unique among Gerronema on account of its fuscous pileus with tiny, dark brown fur or scales, its distinctly radially striping with darkened lines, cheilocystidia present and pileipellis without coarse excrescences. Two species of Omphalina characterized by dark pigments in the pileus–Omphalina depauperata (Singer) Raithelh. and O. subpallida (Singer) Raithelh., formerly named G. subpallidum Singer and G. depauperatum Singer, respectively, have been described from Argentina. These two species most closely resemble G. zhujian but differ in having a hyaline or white stipe, ellipsoid basidiospores, and no cheilocystidia (Singer 1970). Gerronema chrysocarpum is closely allied to G. zhujian on the basis of the dark brown coloration of the umbilicus of its pileus, its whitish stipe, and similarly shaped basidiospores (Liu 1995). This taxon differs from G. zhujian in having a viscid and glabrescent pileus, pale orange lamellar margin, and pleurocystidia (Liu 1995). Other species of Gerronema, such as G. nemorale and G. strombodes, have a distinctly yellow, yellowish orange, olive yellow to yellowish brown pileus, and their micromorphological features are also different (Singer 1970; Antonín et al. 2008; Latha et al. 2018).

Gerronema nemorale Har. Takah.

Figs 11, 12, 13

Description

Pileus 3.0–19.0 mm in diam., hemispherical at first, then convex with a depressed center, applanated and deeply umbilicate with age, slightly striate at the margin in younger basidiomata, slightly translucently striate forming shallow grooves, greenish yellow (2E3), yellowish brown (2D5), olive brown (2E8), always deeper at the center, fading light yellow (5A2) towards the margin, finely tomentose when young, glabrescent with age, with a flat margin. Context white to light yellow, thin. Lamellae moderately distant to distant, decurrent, white or pale yellow (5A2), narrow, edges concolorous with the sides. Stipe 19.0–36.0 × 1.0–2.5 mm, almost equal, but swollen at the base, terete, slender, hollow, pruinose overall, glabrescent with age; base with conspicuous white mycelioid bristles. Odorless, taste mild.

Figure 11. 

Fresh basidiomata of Gerronema nemorale Har. Takah. a–b MY0364 (Wunvfeng, Jian City, Liaoning Province) c MY0113 (Guniujiang, Shitai County, Anhui Province) d MY0264 (Miaoqian Town, Qingyang County, Anhui Province) e MY0248 (Baishanzu, Qingyuan County, Zhejiang Province) f MY0254 (Longquan Mountain, Longquan City, Zhejiang Province) g–h MY0273 (Lanni Lake, Qingtian County, Zhejiang Province) i–j MY0276 (Dayang Mountain, Jinyun County, Zhejiang Province) k–l MY0462 (Baiyun Forest Park, Lishui City, Zhejiang Province) m–n MY0287 (Junzifeng, Sanming City, Fujian Province) o MY0549 (Wuyi Mountain, Nanping City, Fujian Province). Scale bars: 10 mm (a–o). Photographs a–e by Qin Na; f–g by Junqing Yan; h–i by Liangliang Qi; j–o by Yupeng Ge.

Basidiospores [60/3/3] (6.8) 7.9–8.8–9.9 (10.7) × (3.7) 4.6–5.2–5.8 (6.3) μm [Q = 1.59–1.88, Q = 1.70 ± 0.065], narrowly ellipsoid or cylindrical, hyaline, guttulate, thin-walled, inamyloid. Basidia 32–46 × 6–9 μm, hyaline, clavate, 4-spored. Cheilocystidia 27–49 × 5–9 μm, abundant, irregularly cylindric or clavate, colorless. Pleurocystidia absent. Lamellar trama subregular; hyphae 3–9 μm wide, thin-walled, hyaline, inamyloid. Pileus trama subregular, sarcodimitic. Pileipellis hyphae 2–5 μm wide, light yellow (2B2), a cutis; terminal elements cylindric or clavate, 31–50 × 4–9 μm, light yellowish brown (2C4) to yellowish brown (2C6) pigmented, especially in the apex; true pileocystidia absent. Hyphae of the stipitipellis 3–6 μm wide, hyaline, smooth; caulocystidia cylindrical or broadly clavate, 32–48 × 5–8 μm, hyaline, thin-walled. All tissues nonreactive in iodine. Clamps present in all tissues.

Figure 12. 

Morphological features of Gerronema nemorale Har. Takah. (FFAAS0410) a basidiomata b basidia c basidiospores d cheilocystidia e stipitipellis and caulocystidia f pileipellis. Scale bars: 10 mm (a); 10 μm (b–f). Drawing by Qin Na and Yupeng Ge.

Habit and habitat

Solitary to caespitose on dead fallen twigs or rotten wood in mixed broadleaf–conifer forests from early spring to late autumn, common, especially in subtropical zones in China. Subtropical monsoon climate, subtropical humid climate subtropical maritime monsoon climate, or continental monsoon humid climate.

Figure 13. 

Microscopic features of Gerronema nemorale Har. Takah. (FFAAS0410) a–e basidiospores f basidia g–i cheilocystidia j lamellar trama k pileipellis l stipitipellis and caulocystidia. Scale bars: 5 μm (a–e); 10 μm (f–l).

Distribution

Known from Asia (Japan, Korea, Pakistan).

Specimens examined

Anhui Province, Chizhou City, Shitai County, Dayan Village, Guniujiang National Natural Reserve, 7 Jun 2019, Qin Na, Yupeng Ge, Hui Zeng, Junqing Yan, and Liangliang Qi, FFAAS0377 (collection no. MY0113), Qingyang County, Miaoqian Town, 2 Sep 2019, Qin Na, Yupeng Ge, Hui Zeng, Junqing Yan, and Liangliang Qi, FFAAS0384 (collection no. MY0264); Fujian Province, Nanping City, Wuyi Mountain, 10 Aug 2021, Qin Na, Yupeng Ge, Junqing Yan, Zewei Liu, and Yulan Sun, FFAAS0410 (collection no. MY0549), Sanming City, Junzifeng National Natural Reserve, 22 Jun 2021, Qin Na, Yupeng Ge, Binrong Ke, and Liangliang Qi, FFAAS0390 (collection no. MY0287); Zhejiang Province, Lishui City, Qingyuan County, Wangmu, 26 May 2020, Qin Na, Yupeng Ge, Yaping Hu, Junqing Yan, and Zewei Liu, FFAAS0379 (collection no. MY0248); Jilin Province, Tonghua City, Jian City, Wunvfeng National Forest Park, 6 Jul 2021, Qin Na, Yupeng Ge, and Zewei Liu, FFAAS0392 (collection no. MY0364); Zhejiang Province, Lishui City, Longquan City, Zhuangbian Village, 10 Jul 2020, Qin Na, Yupeng Ge, Junqing Yan, and Zewei Liu, FFAAS0382 (collection no. MY0254), Liandu District, Baiyun National Forest Park, 2 Aug 2021, Qin Na, Zewei Liu, FFAAS0395 (collection no. MY0462), Qingtian County, Lanni Lake, 2 Jun 2021, Qin Na, Yupeng Ge, Junqing Yan, Yulan Sun, and Zewei Liu, FFAAS0388 (collection no. MY0273), Jinyun County, Dayang Mountain, 3 Jun 2021, Qin Na, Yupeng Ge, and Junqing Yan, FFAAS0389 (collection no. MY0276).

Remarks

Having a sarcodimitic tissue structure, G. nemorale fits well within the currently restricted concept of the genus Gerronema (Redhead 1986; Norvell et al. 1994). Gerronema nemorale seems to be rather common in the East Asian region (Takahashi 2000; Antonín et al. 2008; Kim et al. 2014; Aqdus and Khalid 2021). Kim et al. (2014) has reported a basidiospore size of 6.0–8.2 × 3.5–4.8 μm for G. nemorale collected from Mount Halla (Jeju Island) in southwestern Korea, which is distinctly smaller than that of other specimens from Korea, Japan, Pakistan, and our collections (Takahashi 2000; Antonín et al. 2008; Kim et al. 2014; Aqdus and Khalid 2021). Gerronema tenue Dennis, described from Venezuela, is allied with G. nemorale, but the latter differs in having a citrine yellow pileus, an insititious stipe, and lamellae edges without cheilocystidia (Dennis 1961). Another similar species, G. corticiphilum Lj.N. Vassiljeva, described as G. corticiphila, has a rarely sulfurous-colored pileus and larger and narrower basidiospores (13–17 × 4–5 μm) (Vassiljeva 1973). In addition, G. icterinum (Singer) Singer from South America, now treated as Trogia icterina (Singer) Corner, shows some similarities with G. nemorale but has veined and forked lamellae and lacks cheilocystidia (Singer 1986). Another species of Trogia, T. mellea Corner, is also similar to G. nemorale, but can be easily distinguished from the latter in having no olivaceous tones on the pileus surface, a fuscous, pruinose pileus center and stipe, and subclavate or subventricose cheilocystidia (Corner 1966).

Discussion

Our phylogenetic analysis divided Gerronema into several highly supported clades containing other members of Porotheleaceae, thus providing further evidence that Gerronema is polyphyletic (Vizzini et al. 2019). This finding is consistent with the view of Vizzini et al., who only included seven genera in Porotheleaceae: Hydropus, Chrysomycena, Clitocybula, Leucoinocybe, Megacollybia, Porotheleum, and Trogia; in addition, many taxa in this family in the sense of Redhead have a sarcodimitic structure (Redhead 1986; Vizzini et al. 2019). The phylogenetic results are in agreement with the taxonomic concept of Gerronema as a heterogeneous group. Although Gerronema was treated after its establishment as a subgenus of Omphalina by Lange (1981), the view of Gerronema as a distinct genus has been widely adopted (Redhead 1986; Norvell et al. 1994).

The phylogenetically and morphologically closest genera to Gerronema are Megacollybia and Trogia (Hughes et al. 2007; Antonín et al. 2019; Vizzini et al. 2019). Compared with Gerronema, however, Megacollybia is well characterized by the presence of rhizomorphs at the base of stipe and a sarcodimitic stipe structure, whereas narrow and frequently forked gills and a trichodermic pileipellis are observed in Trogia (Corner 1966; Hughes et al. 2007). Other groups in the same family, namely, Hydropus, Chrysomycena, Clitocybula, Leucoinocybe, and Porotheleum, have different morphological characteristics and are genetically distant from Gerronema (Hausknecht et al. 1997; Antonín et al. 2008, 2019; Vizzini et al. 2019).

Since 1995, only three species of Gerronema have been reported from China, namely, G. albidum (Fr.) Singer, G. chrysocarpum P.G. Liu, and G. indigoticum T. Bau & L.N. Liu (Liu 1995; Dai et al. 2010; Liu et al. 2019). The distinctly white and blue basidiomata of G. albidum and G. indigoticum can be used to distinguish those two species from our newly described and newly recorded species, and G. chrysocarpum has a viscid pileus and pleurocystidia (Liu 1995; Dai et al. 2010; Liu et al. 2019).

Key to seven species of Gerronema in China

1 Basidiomata not yellow or brown 2
Basidiomata yellow to brown 3
2 Pileus and stipe blue G. indigoticum
Pileus and stipe white G. albidum
3 Pleurocystidia present G. chrysocarpum
Pleurocystidia absent 4
4 Pileus densely covered with deep brown fur or scales G. zhujian
Pileus without fur or scales 5
5 Basidiomata distinctly small (Pileus < 9 mm in diam.) G. microcarpum
Basidiomata moderately small (Pileus > 9 mm in diam.) 6
6 Cheilocystidia up to 48 μm G. baishanzuense
Cheilocystidia less than 35 μm G. nemorale

Morphological and molecular evidence support classification of the four newly recognized/recorded species as members of Gerronema. The four species share an umbonate or infundibuliform pileus, decurrent lamellae, inamyloid basidiospores, clavate cystidia, and sarcodimitic tramal tissues. In addition, the four species are lignicolous in habit, growing on rotten wood or fallen twigs. Gerronema microcarpum is mainly distinguished from G. baishanzuense, G. nemorale, and G. zhujian by its distinctly small basidiomata and basidiospores. The tiny brown fur or scales on the pileus of G. zhujian differentiate it from the other three species. Gerronema nemorale is morphologically most similar to G. baishanzuense but can be readily discriminated on the basis of its olive-tinted pileus, larger basidiospores, and smaller caulocystidia.

Significantly, the phylogenetic relationship of G. subclavatum to G. nemorale remains unresolved given the limited genetic differentiation between these two taxa (Cooper 2014; Latha et al. 2018; Antonín et al. 2019; Vizzini et al. 2019). Gerronema subclavatum was formerly classified as a species in Omphalina; the original description is as follows: "Pileus thin, submembranaceous, subclavate or tubaeform, deeply umbilicate, glabrous, grayish brown, 6–12 mm. broad; lamellae subdistant, very decurrent, yellow; stem slender, subpruinose, often tomentose near the base, hollow, whitish, about 2.5 cm. long, 1 mm. thick; spores elliptic, 6–7.5 μm long, 4–5 μm broad" (Peck 1900). A new combination, G. subclavatum, was later proposed, but a detailed description was not provided (Singer 1970; Redhead 1986). Taking into account the grayish brown pileus, whitish stipe, and smaller basidiospores of G. subclavatum, we believe that this species is morphologically distinct from G. nemorale. We therefore tentatively accept G. subclavatum and G. nemorale as two independent taxa but emphasize that sufficient sampling and a detailed appraisal of the morphological and molecular variation of G. subclavatum and G. nemorale are required to confirm this hypothesis.

Acknowledgements

This study was supported by the Natural Science Foundation of Shandong Province (grant no. ZR2020QC001), the National Natural Science Foundation of China (grant no. 3190012), the Natural Science Foundation of Shandong Province (grant no. ZR2019PC028), the Shandong Agricultural Industry Technology System (2021 grant no. 26, SDAIT-07-03), the Central Public-Interest Scientific Institution Basal Research Fund (grant no. GYZX200203), the Project of Biological Resources Survey in Wuyishan National Park (grant no. HXQT2020120701), the Project of Biodiversity Conservation in Lishui, Zhejiang Province (grant no. HXYJCP2021110648), the Biodiversity investigation, observation and assessment program of Ministry of Ecology and Environment of China (grant no. 2110404 and 2019-2023), and the Cooperation Project of University and Local Enterprise in Yantai of Shandong Province (grant no. 2021XDRHXMPT09). We sincerely thank Dr Liangliang Qi (Microbiology Research Institute, Guangxi Academy of Agricultural Sciences), Dr Junqing Yan (Jiangxi Agriculture University), Mr Binrong Ke (Institute of Edible Fungi, Fujian Academy of Agricultural Sciences), Mr Zhiheng Zeng (Institute of Edible Fungi, Fujian Academy of Agricultural Sciences), Mr Xiaojian Wu (Microbiology Research Institute, Guangxi Academy of Agricultural Sciences), Ms Liying Li (Microbiology Research Institute, Guangxi Academy of Agricultural Sciences), Ms Zewei Liu (Ludong University), and Mr Feng Wang (Shutterbug) for their kind help during field work.

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