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Phylogenetic overview of Aureoboletus (Boletaceae, Boletales), with descriptions of six new species from China
expand article infoMing Zhang, Tai-Hui Li, Chao-Qun Wang§, Nian-Kai Zeng|, Wang-Qiu Deng§
‡ Guangdong Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, China
§ Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangzhou, China
| Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Haikou, China
Open Access

Abstract

In this study, species relationships of the genus Aureoboletus were studied, based on both morphological characteristics and a four-gene (nrLSU, tef1-a, rpb1 and rpb2) phylogenetic inference. Thirty-five species of the genus have been revealed worldwide, forming eight major clades in the phylogenetic tree, of which twenty-four species have been found in China, including six new species: A. glutinosus, A. griseorufescens, A. raphanaceus, A. sinobadius, A. solus, A. velutipes and a new combination A. miniatoaurantiacus (Bi & Loh) Ming Zhang, N.K. Zeng & T.H. Li proposed here. A key to 24 known Chinese species has been provided.

Keywords

Boletes, molecular phylogeny, morphology, species identification, taxonomy

Introduction

Aureoboletus Pouzar was circumscribed in 1957, based on the type species A. gentilis (Quél.) Pouzar (Pouzar 1957). It was characterised by its slimy basidiomata, glabrous to subglabrous pileus and golden yellow hymenophore unchanging when dry (Quélet 1884; Saccardo 1888; Pouzar 1957). To date, 35 species have been described worldwide, 15 of which were originally described in China (Patouillard 1895; Shi and Liu 2013; Zhang et al. 2014, 2015a, b, 2017; Zeng et al. 2015; Li et al. 2016; Wu et al. 2016; Fang et al. 2019). Aureoboletus species can be found in tropical, subtropical and temperate regions of different continents, but most known species appear to exist in Asia and North America. Interestingly, they are strongly implicated as symbionts with an array of ectotrophic plants of the Fagaceae and Pinaceae families (Pouzar 1957; Yang et al. 2003; Klofac 2010; Shi and Liu 2013; Halling et al. 2015; Zeng et al. 2015; Wu et al. 2016; Zhang et al. 2017).

The establishment and acceptance of the genus Aureoboletus has a long history. Xerocomus section Auripori Singer (1942) was established to accommodate Aureoboletus-like taxa. Later, Auripori species were transferred to the genus Pulveroboletus Murrill (Singer 1947). For a long time, the genus Aureoboletus was not accepted as an independent genus by some mycologists (Smith and Thiers 1971; Corner 1972; Singer 1986; Both 1993; Bessette et al. 2000; Šutara 2005) and species with viscid basidiomata and vivid yellow hymenophores were variously placed in genera Boletellus Murrill, Boletus L., Pulveroboletus and Xerocomus Quél. (Singer 1942, 1947, 1986; Smith and Thiers 1971; Corner 1972; Both 1993; Bessette et al. 2000); However, Aureoboletus was accepted as an independent genus by other mycologists and the features of the genus were redefined (Watling 1965; Watling 2008; Hongo 1973; Zang 1993; Šutara 2008; Klofac 2010). A world-wide survey of the genus, based on morphological characteristics, was conducted and a key was designed to aid in the identification of 11 global Aureoboletus species (Klofac 2010).

Recently, broad-scale molecular phylogenetic studies have been used to investigate phylogenetic relationships amongst the genera and species in Boletes. Aureoboletus was strongly supported as a genus in the Boletaceae, subfamily Xerocomoideae and has been shown to be closely related to Boletellus, Hemileccinum Šutara, Heimioporus E. Horak, Xerocomus etc. (Binder 1999; Binder and Hibbett 2006; Nuhn et al. 2013; Wu et al. 2014, 2016). The genus Sinoboletus M. Zang, originally described in south-western China, was proven to be a synonym of Aureoboletus (Zang 1992; Wu et al. 2014); Boletellus projectellus (Murrill) Singer, B. mirabilis (Murrill) Singer, B. russellii (Frost) E.-J. Gilbert and Pulveroboletus auriflammeus (Berk. & M.A. Curtis) Singer) were transferred into the genus Aureoboletus, based on both morphological and molecular data (Halling et al. 2015; Wu et al. 2016).

Numerous Aureoboletus specimens have been recently obtained in China, increasing the species diversity of Aureoboletus. In this study, the species richness and phylogenetic relationships were re-evaluated, based on detailed morphological observations and a four-gene phylogenetic inference. The aims were to 1) evaluate the phylogenetic relationships within the genus; 2) redefine the characteristics of Aureoboletus; 3) elucidate the species diversity of Aureoboletus in China; 4) describe the newly discovered species.

Materials and methods

Morphological studies

Photographs and records of basidiomata were obtained in the field. Specimens were dried in an electric drier and finally deposited in the Fungarium of Guangdong Institute of Microbiology (GDGM) or the Fungal Herbarium of Hainan Medical University (FHMU), Haikou City, Hainan Province, China. Descriptions of macro-morphological characters and habitats were obtained with photographs and field notes. Colours were described in general terms with serial numbers, for example, reddish-brown (9D8–9E8), following Kornerup and Wanscher (1978). Micro-morphological features were observed from dried materials after sectioning and mounting in 5% potassium hydroxide (KOH) solution and 1% Congo Red or Melzer’s reagent under a light microscope (Olympus BX51, Tokyo, Japan). For basidiospore descriptions, an abbreviation [n/m/p] denotes n spores measured from m basidiomata of p collections; a notation (a–)b–c(–d) describes basidiospore dimensions, where the range b–c represented 90% or more of the measured values and ‘a’ and ‘d’ were the extreme values; Q referred to the length/width ratio of an individual basidiospore and Qm referred to the average Q value of all basidiospores ± sample standard deviation. All line-drawings of microstructures were made, based on rehydrated materials.

DNA extraction, PCR amplification and sequencing

Genomic DNA was extracted from the voucher specimens using the Sangon Fungus Genomic DNA Extraction kit (Sangon Biotech Co. Ltd., Shanghai, China), according to the manufacturer’s instructions. Primer pairs LR0R/LR5 or LR0R/LR7 (Vilgalys and Hester 1990), EF1-B-F1/EF1-B-R, RPB1-B-F/RPB1-B-R and RPB2-B-F1/RPB2-B-R (Wu et al. 2014) were used for the amplification of the large subunit nuclear ribosomal RNA (nrLSU) region, the translation elongation factor 1-alpha subunit (tef1-a), the largest subunit of RNA polymerase II (rpb1) and the second largest subunit of RNA polymerase II (rpb2), respectively. Polymerase Chain Reaction was performed in a total volume of 25 μl containing 1 μl template DNA, 9.5 μl distilled water, 1 μl of each primer and 12.5 μl PCR mix [DreamTaqtm Green PCR Master Mix (2×), Fermentas]. Amplification reactions were performed in a Tprofessional Standard thermocycler (Biometra, Göttingen, Germany) under the following conditions: at 95 °C for 4 min, then 35 cycles of denaturation at 95 °C for 60 s, annealing at 53 °C (LSU) /55 °C (tef1-a, rpb1 and rpb2) for 60 s and extension at 72 °C for 80 s, with a final extension at 72 °C for 8 min. The PCR products were electrophoresed on 1% agarose gels with known standard DNA markers and sequences were performed on an ABI Prism 3730 Genetic Analyzer (PE Applied Biosystems, Foster, CA, USA) at Beijing Genomic Institute (BGI) using the same primers. The raw sequences were assembled with SeqMan implemented in Lasergene v7.1 (DNASTAR Inc., USA). The assembled sequences of the specimens were submitted to GenBank.

Phylogenetic analyses

Newly generated sequences and related sequences downloaded from GenBank were used to reconstruct phylogenetic trees. Detailed information of samples, including species name, voucher, locality, GenBank accession numbers and references, are given in Table 1. Four sequence datasets (nrLSU, tef1-a, rpb1 and rpb2) were separately aligned with MAFFT v6.853 using the E-INS-i strategy (Katoh et al. 2002) and examined in Bioedit v7.0.9 (Hall 1999). The four datasets were analysed independently using the Maximum Likelihood (ML) method to detect the topologies of the four genes. Since no significant incongruence was detected (BS > 70%), the four single-gene alignments were concatenated using Phyutility 2.2 (Smith and Dunn 2008). Missing fragments of some gene markers of several specimens were coded as missing data, intron regions of protein-coding genes were retained in the final analyses and the ambiguously aligned regions were detected and excluded with Gblocks (Castresana 2000).

Information of samples used in this study.

Taxon Voucher Country LSU tef1 rpb1 rpb2 Reference
A. auriflammeus DD973 USA AY612818 _ _ _ GenBank
A. auriporus MAN020 Costa Rica JQ003659 _ _ _ Neves et al. 2012
BDCR0431 Costa Rica HQ161871 _ HQ161840 _ Dentinger et al. 2010
A. cf. auriporus GDGM 44404 USA MN410705 _ _ _ This study
A. catenarius GDGM 45142 China MN204514 _ MN473157 _ This study
HKAS54463 China KT990509 KT990710 KT990890 KT990348 Wu et al. 2016
HKAS54467 China KT990510 KT990711 _ KT990349 Wu et al. 2016
A. citriniporus REH8719 USA KF030298 _ _ _ Nuhn et al. 2013
A. clavatus GDGM42992 China MK123462 MK165847 _ _ Zeng et al. 2015
GDGM42962 China KR052045 MK165846 KR052056 _ Zeng et al. 2015
GDGM42963 China KR052046 KR052054 KR052057 _ Zeng et al. 2015
GDGM42984 China KR052047 KR052055 _ _ Zeng et al. 2015
A. duplicatoporus GDGM 49451 China MN204515 _ MN473160 _ This study
GDGM 53135 China MN204517 MN549677 MN473167 _ This study
GDGM 53134 China MN204516 _ MN473166 MN549707 This study
GDGM 52898 China MN410708 _ MN473164 _ This study
GDGM 53181 China MN204518 MN549669 MN473168 _ This study
GDGM 71293 China MN204519 _ MN473173 _ This study
GDGM 71724 China MN204520 _ MN473175 _ This study
HKAS50498 China KF112361 KF112230 KF112561 KF112754 Wu et al. 2016
HKAS63009 China KT990511 KT990712 KT990891 KT990350 Wu et al. 2016
HKAS83115 China KT990512 KT990713 KT990892 KT990351 Wu et al. 2016
GDGM45133 China MK123455 MK165834 _ MN549697 This study
GDGM52889 China MK123456 MK165835 MN473163 _ This study
A. formosus GDGM44441 China KT291749 KT291744 MN473152 KT291751 Zhang et al. 2015
GDGM44444 China KT291750 MK165833 MN473153 KT291752 Zhang et al. 2015
A. gentilis Pug1 Germany DQ534635 KF030399 _ _ Nuhn et al. 2013
MG372a Italy KF112344 KF134014 KF112557 KF112741 Wu et al. 2014
A. glutinosus GDGM 55717 China MN204522 _ _ _ This study
GDGM 45927 China MN204521 _ - MN549699 This study
GDGM44476 China MH670254 MH700192 _ MH700228 This study
GDGM44477 China MH670255 MH700205 _ MH700229 This study
GDGM44479 China MH670256 MH700204 _ MH700230 This study
GDGM44733 China MH670257 MH700203 _ MH700231 This study
GDGM44821 China MH670258 _ _ MH700232 This study
A. griseolorufescens GDGM28490 China MH670278 _ _ MH700241 This study
ZhangM131 China MH670279 _ MH700220 MH700242 This study
A. innixus 136/98 USA DQ534639 _ _ _ Binder and Hibbett 2007
MB03-104 USA KF030239 KF030400 _ _ Nuhn et al. 2013
136 USA KF030240 _ _ _ Nuhn et al. 2013
A. liquidus TNS:F-39710 Japan AB972886 _ _ _ Terashima et al. 2016
TNS:F-52265 Japan AB972884 _ _ _ Terashima et al. 2016
TNS:F-52267 Japan AB972885 _ _ _ Terashima et al. 2016
A. longicollis GDGM 70547 China MN204526 _ MN473172 _ This study
GDGM 75292 China MN204527 _ MN473179 _ This study
GDGM 49735 China MN204525 _ MN473161 _ This study
GDGM 43502 China MN204524 _ MN473150 MN549688 This study
ZhangM56 China MN204528 _ MN473187 _ This study
GDGM43239 China MK123459 MK165843 MN473147 _ This study
HKAS80127 China KT990515 KT990719 _ _ Zeng et al. 2015
GDGM42849 China KR052051 _ KR052058 _ Zeng et al. 2015
HKAS53398 China KF112376 KF112238 KF112625 KF112755 Zeng et al. 2015
HKAS84679 China KT990514 KT990718 _ KT990356 Zeng et al. 2015
HKAS80489 China KT990523 KT990727 _ KT990364 Zeng et al. 2015
GDGM44734 China MK123458 MK165842 MN473155 MN549692 This study
GDGM53336 China MK123460 MK165844 MN473170 MN5497018 This study
GDGM44739 China MK123461 MK165845 MN473156 MN549693 This study
A. marronius GDGM43288 China KJ488958 KT291746 _ KT291753 Zhang et al. 2014
A. miniatoaurantiacus GDGM 75495 China MN204533 _ MN473181 MN549711 This study
GDGM 53350 China MN204532 MN549678 MN473171 MN549709 This study
GDGM 43437 China MN204530 _ MN473149 MN549687 This study
GDGM 43282 China MN204529 MN549671 MN473148 MN549686 This study
GDGM 44727 China MN204531 _ MN473154 MN549691 This study
GDGM53501 China MH670262 MH700199 MH700217 _ This study
Zeng1625 China MH670263 _ _ _ This study
Zeng1294 China MH670264 MH700198 _ _ This study
Zeng1323 China MH670265 MH700197 _ _ This study
Zeng1339 China MH670266 MH700196 _ _ This study
Zeng664 China MH670267 MH700195 _ _ This study
HKAS59694 China KT990513 KT990714 KT990893 KT990352 Wu et al. 2016
GDGM42855 China MH670259 MH700202 MH700214 MH700233 This study
GDGM53274 China MH670260 MH700201 MH700215 MH700234 This study
GDGM52888 China MH670261 MH700200 MH700216 MH700235 This study
A. mirabilis REH9765 USA KP327661 KP327661 _ _ Halling et al. 2015
CBS-136.60 Germany AF050652 _ _ _ Binder and Fischer 1997
HKAS57776 China KF112360 KF112229 KF112624 KF112743 Wu et al. 2014
REH8717 USA KF030299 _ _ _ Nuhn et al. 2013
A. moravicus Xle1 Germany _ KF030403 _ _ Nuhn et al. 2013
MG374a Italy KF112421 KF112232 KF112559 KF112745 Wu et al. 2014
A. nephrosporus HKAS67931 China KT990516 KT990720 KT99089 KT990357 Wu et al. 2016
HKAS74929 China KT990517 KT990721 KT990896 KT990358 Wu et al. 2016
A. novoguineensis K-A/7 Japan DQ534637 _ _ _ Binder and Hibbett 2007
A. projectellus MB-03-118 USA NG027638 _ _ _ GenBank
NYBG13392 USA KP327622 KP327675 _ _ Halling et al. 2015
Sn2Hor USA KF030300 _ _ _ Nuhn et al. 2013
NYBG13393 USA KP327623 KP327676 _ _ Halling et al. 2015
ID-713 USA DQ534582 AY879116 AY788850 AY787218 Binder and Hibbett 2007
A. quercus-spinosae GDGM 43757 China KY039966 MK165839 KY039962 KY039957 Zhang et al. 2017
GDGM43757 China KY039966 MK165839 KY039962 KY039957 Zhang et al. 2017
GDGM43755 China KY039967 MK165836 KY039963 KY039958 Zhang et al. 2017
GDGM43758 China KY039968 MK165837 KY039964 KY039959 Zhang et al. 2017
GDGM43786 China KY039969 MK165838 KY039965 KY039960 Zhang et al. 2017
A. raphanaceus GDGM 45966 China MN204536 MN549673 _ MN549700 This study
GDGM 52266 China MN204538 MN549674 _ MN549702 This study
GDGM 45911 China MN204535 _ _ MN549698 This study
GDGM 52908 China MN204539 MN549675 _ _ This study
GDGM 49634 China MN204537 _ _ MN549701 This study
GDGM 53127 China MN204540 MN549676 MN473165 MN549706 This study
GDGM 75476 China MN204541 _ MN473166 MN549707 This study
GDGM 42937 China MN204534 _ MN473146 MN549685 This study
GDGM52543 China MH670271 _ _ _ This study
GDGM44832 China MH670268 MH700194 MH700218 MH700236 This study
GDGM50266 China MH670269 _ _ MH700237 This study
GDGM46333 China MH670270 _ _ MH700238 This study
GDGM52590 China MH670272 MH700193 MH700219 MN549704 This study
A. roxanae DS626-7 USA KF030311 KF030402 KF030381 _ Nuhn et al. 2013
A. rubellus GDGM52382 China MH670273 _ _ MH700239 This study
GDGM52367 China MH670274 _ _ MH700240 This study
A. shichianus HKAS43373 China AY647211 _ _ _ GenBank
HKAS76852 China KF112419 KF112237 KF112562 KF112756 Wu et al. 2014
A. sinobadius GDGM75499 China MN204551 _ MN473182 _ This study
GDGM 70666 China MN204547 _ _ _ This study
GDGM 49747 China MN204546 _ _ _ This study
GDGM 49670 China MN204545 _ _ _ This study
GDGM 71932 China MN204548 _ MN473176 _ This study
A. sinobadius GDGM 49482 China MN204544 _ _ _ This study
GDGM 72253 China MN204549 _ MN473177 _ This study
GDGM 49432 China MN204543 _ MN473159 _ This study
GDGM 75477 China MN204550 _ MN473180 _ This study
GDGM44473 China MH670250 MH700189 MH700211 _ This study
GDGM43275 China MH6702464 MH700185 MH700208 MH700221 This study
GDGM44732 China MH670247 MH700186 MH700207 MH700222 This study
GDGM44730 China MH670248 MH700187 MH700209 MH700223 This study
GDGM44736 China MH670249 MH700188 MH700210 MH700224 This study
A. solus GDGM46222 China MH670275 _ _ _ This study
GDGM44759 China MH670276 MH700206 _ _ This study
GDGM42822 China MH670277 _ _ _ This study
GDGM 49600 China MN410707 _ _ _ This study
GDGM 49404 China MN204553 _ _ _ This study
GDGM 46807 China MN204552 _ _ _ This study
GDGM 72441 China MN204555 _ _ _ This study
GDGM 70342 China MN204554 _ _ _ This study
Aureoboletus sp. GDGM 49259 China MN410706 _ MN473158 _ This study
GDGM 71707 China MN204556 _ MN473174 MN549710 This study
GDGM 75305 China MN204513 _ _ _ This study
GDGM 70474 China MN204511 _ _ _ This study
GDGM 72473 China MN204512 _ _ _ This study
GDGM 44470 China MN204509 MN549672 _ MN549680 This study
GDGM 52298 China MN204523 _ MN473162 MN549703 This study
LAM-0466 Malaysia KY091058 _ _ _ GenBank
HKAS53458 China KF112456 KF112231 KF112558 KF112742 This study
GDGM44829 China KY039970 _ _ KY039961 This study
GDGM44831 China KY039971 MK165840 _ MN549696 This study
GDGM44469 China KP319028 MK165841 _ MN549690 This study
A. tenuis GDGM42601 China KF534789 KT291745 _ KT291754 Zhang et al. 2013
A. thibetanus HKAS76655 China KF112420 KF112236 KF112626 KF112752 Wu et al. 2014
GDGM43283 China KJ907380 KT291747 _ KT291755 Zhang et al. 2014
GDGM43284 China KJ90738 KT291748 _ KT291756 Zhang et al. 2014
HKAS57692 China KT990524 KT990728 KT990901 KT990365 Wu et al. 2016
HKAS89494 China KT990525 KT990729 KT990902 KT990366 Wu et al. 2016
A. velutipes GDGM52409 China MH670252 _ _ MH700225 This study
GDGM44713 China MH670253 MH700191 MH700213 MH700226 This study
GDGM42608 China MH670251 MH700190 MH700212 MN549683 This study
A. cf. venustus ZhangM142 China MN204558 MN549668 MN473186 MN549714 This study
A-2 China MN204557 MN549679 MN473185 MN549713 This study
GDGM42800 China MK123463 _ MN473187 MN549684 This study
A. venustus HKAS82183 China KU321705 _ _ _ Li et al. 2016
HKAS77700 China KU321703 _ _ _ Li et al. 2016
A. viridiflavus DD972 USA AY612805 _ _ _ GenBank
A. viscidipes GDGM 44818 China MN204510 _ _ MN549694 This study
HKAS77103 China KT990519 KT990723 _ KT990360 Wu et al. 2016
GDGM44820 China MK123457 _ _ MN549695 This study
A. yunnanensis GDGM 26359 China MN204560 MN549670 MN473145 MN549681 This study
GDGM 24560 China MN204559 _ MN473144 MN549682 This study
HKAS57581 China KF112422 KF112233 KF112560 KF112746 Wu et al. 2016
HKAS75050 China KT990520 KT990724 KT990898 KT990361 Wu et al. 2016
A. zangii GDGM 75881 China MN204563 - MN473183 MN549712 This study
GDGM 28577 China MN204561 _ _ _ This study
GDGM 44406 China MN204562 _ MN473151 MN549689 This study
HKAS63217 China KT990526 _ _ _ Wu et al. 2016
HKAS74751 China KT990521 KT990725 KT990899 KT990362 Wu et al. 2016
HKAS74766 China KT990522 KT990726 KT990900 KT990363 Wu et al. 2016
P. imbricatus HKAS68642 China KF112398 KF112299 KF112637 KF112786 Wu et al. 2014
X. aff. subtomentosus HKAS58865 China KF112389 KF112294 KF112630 KF112784 Wu et al. 2014

The combined final dataset was analysed using RAxML v7.2.6 (Stamatakis 2006) and MrBayes v3.1.2 (Ronquist and Huelsenbeck 2003) for Maximum Likelihood (ML) and Bayesian Inference (BI), respectively. For both BI and ML analyses, the substitution model, suitable for each gene partition, was determined using the Akaike Information Criterion (AIC), complemented in MrModeltest v2.3 (Nylander 2004). All parameters in the ML analysis were kept as defaults except for choosing GTRGAMMAI as the model and statistical supports were obtained using rapid non-parametric bootstrapping with 1000 replicates; BI analysis using 4 chains were conducted by setting generations to 80 million and stoprul command with the value of stopval set to 0.01, trees were sampled every 100 generations, the first 25% generations were discarded as burn-ins and posterior probabilities (PP) were then calculated from the posterior distribution of the retained Bayesian trees. Phylloporus imbricatus N.K. Zeng, Zhu L. Yang & L.P. Tang and Xerocomus subtomentosus (L.) Quél. were selected as outgroups, based on Wu et al. (2016) and Zhang et al. (2017).

Results

Molecular phylogenetic results

For phylogenetic analyses, 304 (102 nrLSU, 59 tef1-a, 71 rpb1 and 72 rpb2) new sequences from 105 Aureoboletus collections and 171 GenBank downloaded sequences from 68 Aureoboletus samples were used as ingroups. Four sequences of P. imbricatus and X. subtomentosus, respectively, retrieved from GenBank were used as outgroups. The combined matrix of 175 samples with 3018 nucleotide sites was submitted to TreeBASE (Submission ID 25249). HKY+G, GTR+I+G, SYM+I and SYM+G were chosen as the best substitution models for nrLSU, tef1-a, rpb1 and rpb2, respectively. ML and BI analyses generated almost identical tree topologies with minimal variations in statistical support values. Thus, only a ML tree is displayed (Fig. 1).

Figure 1. 

Maximum likelihood tree from a RAXML search using the GTRGAMMA model, illustrating the phylogeny of Aureoboletus and related taxa in Boletales, based on a multilocus (nrLSU, tef1-a, rpb1 and rpb2) dataset. Phylloporus imbricatus N.K. Zeng, Zhu L. Yang & L.P. Tang and Xerocomus subtomentosus (L.) Quél. are chosen as outgroups. The lineages with new species and new combination are bold in the tree. Branches are labelled with maximum likelihood bootstrap higher than 70% and Bayesian posterior probabilities more than 0.95.

In the multi-gene phylogenetic trees, the monophyly of Aureoboletus was statistically strongly supported (BS = 100, PP = 1); eight well supported main clades, labelled as Clade I to VIII, are shown and six well supported (BS = 100, PP = 1) new species lineages were recognised. In Clade I, nine known species [A. auriporus (Peck) Pouza, A. duplicatoporus (M. Zang) G. Wu & Zhu L. Yang, A. formosus Ming Zhang & T.H. Li, A. gentilis (Quél.) Pouzar, A. novoguineensis Hongo, A. quercus-spinosae Ming Zhang & T.H. Li, A. venustus Fang Li, Kuan Zhao & Qing Li Deng, A. viridiflavus Coker & Beers ex Klofac and A. zangii X.F. Shi & P.G. Liu] were presented, including the type species A. gentilis and a new lineage (lineage I) discovered in this study. Lineage I is presented as a sister group to A. novoguineensis with significant statistical support (BS = 100, PP = 1). Clade II comprised five known species [A. catenarius G. Wu & Zhu L. Yang, A. citriniporus (Halling) Klofac, A. moravicus (Vaček) Klofac, A. roxanae (Frost) Klofac and A. yunnanensis G. Wu & Zhu L. Yang], a new lineage (lineage II) and three unnamed sequences. Lineage II is closely related to an unnamed sample (GDGM71707) from southern China. Clade III is composed of six species, [A. longicollis (Ces.) N.K. Zeng & Ming Zhang, A. marroninus T.H. Li & Ming Zhang, A. tenuis T.H. Li & Ming Zhang, A. thibetanus (Pat.) Hongo & Nagas., A. viscidipes (Hongo) G. Wu & Zhu L. Yang] and a new lineage (lineage III), all of which are from Asia. Clade IV was comprised of the North American species A. auriflammeus (Berk. & M.A. Curtis) G. Wu & Zhu L. Yang and a new species combination from China. Clade V included five strongly supported species level groups [A. innixus (Frost) Halling, A.R. Bessette & Bessette, A. nephrosporus G. Wu & Zhu L. Yang, A. rubellus Kuan Zhao & G. Wu] and two new lineages (lineage IV and lineage V). Clade VI included four known species [A. mirabilis (Murrill) Halling, A. projectellus (Murrill) Halling, A. russellii (Frost) G. Wu & Zhu L. Yang from North America and A. shichianus (Teng & L. Ling) G. Wu & Zhu L. Yang from China]. Clade VII had a single species, A. clavatus N.K. Zeng & Ming Zhang, which was recently reported in southern China. Clade VIII represents a single new lineage (lineage VI), which is the basal group of the genus Aureoboletus.

Taxonomy

Aureoboletus Pouzar, Česká Mykol. 11: 48, 1957.

Type species

. Aureoboletus gentilis (Quél.) Pouzar.

Description

Basidiomata small to large. Pileus viscid, dry or sticky when wet, even or smooth to wrinkled, usually subtomentose, rarely glabrous, with or without veil or velar residues hanging at margin. Context white to yellowish-white, usually pinkish to reddish-brown beneath pileipellis, unchanging or changing blue or greenish or pastel red when exposed. Tubes coloured with all kinds of yellows, pale yellow, golden yellow to bright yellow, unchanging or slightly changing to blue when bruised, pores circular to angular, smaller to larger, somewhat relatively larger and shallowly depressed around the stipe, concolorous with tubes. Stipe central, cylindrical or clavate, surface glabrous to striate fibrillose, never or rare forming reticulation or Leccinum-like scabrous, dry to viscid, with white basal mycelium. Basidiospores smooth to verrucose or longitudinally striate, subfusiform, oblong ovoid to subglobose, yellowish to yellowish-brown in KOH. Hymenophoral trama boletoid, composed of subcylindrical to cylindrical hyphae, colourless. Pleurocystidia fusiform to subclavate, thin- or thick-walled, sometimes containing golden-yellow contents at first, then gradually changing to yellowish-white to hyaline in 5% KOH. Cheilocystidia present, infrequent or absent, usually similar to pleurocystidia in shape and size, if present. Pileipellis as an interwoven trichoderm, trichoderm or ixotrichoderm, consisting of erect hyphae which are occasionally branched, cylindrical to clavate, thin- to slightly thick-walled, usually less than 1 μm. Stipitipellis hymeniform, as an ixotrichoderm to intricated ixotrichoderm. Caulocystidia clavate, fusoid or ventricose-fusoid. Stipe trama composed of parallel hyphae. Clamp connections absent.

Distribution and ecology

World-wide distribution, mainly known from subtropical Asia and temperate zones of the Northern hemisphere, growing on the ground associated with Fagaceae and other broadleaf trees.

Descriptions of six new species and one new combination of Aureoboletus

Aureoboletus glutinosus Ming Zhang & T.H. Li, sp. nov.

MycoBank No: 827103
Figs 2A, B, 3A, 4A–E

Diagnosis

This species is distinguished from other Aureoboletus taxa by its smaller and glutinous basidiomata, reddish-brown to ruby pileus usually with irregular reticulation and darker folds, gelatinised veil remnants and smooth basidiospores 10–13.5 × 4.5–5 µm in size.

Etymology

glutinosus” refers to the glutinous basidiomata.

Type

China, Hunan Province, Rucheng Town, Jiulongjiang National Forest Park, on soil and usually growing amongst the mosses under the broadleaf forest, at 25°38'N, 113°77'E, alt. 300 m, 8 May 2014, M. Zhang (holotype: GDGM44477).

Description

Basidiomata small-sized. Pileus 1–2 cm wide, obtuse to convex, becoming broadly convex to plane, fleshy, viscid, especially when young and wet, reddish-brown, violet brown to greyish-ruby (9E6–12E6, 9E7–12E7), slightly fading to pale yellow (2A3–4A3) towards margin, usually forming a pale yellow to even nearly white zone at margin, distinctly wrinkled and often reticulate irregularly with somewhat darker folds at centre, strongly glutinous or mucilaginous when fresh; margin somewhat involute to nearly flat, often attached with yellowish-white to subhyaline and strongly gelatinised veil remnants. Context 2–5 mm thick at stipe, firm and tough in youth, soft when matured, white on the whole, greyish-red (10B5–11B5) beneath pileipellis, practically unchanging to becoming slightly greyish-pinkish or greyish-red (10B5–11B5) when exposed. Tubes 7–10 mm deep, distinctly depressed around stipe, yellowish-white (2A2–4A2) when young, becoming pale yellow, greyish-yellow, pastel yellow to olive yellow (2A3–4A3, 1B3–2B3, 2A4–3A4, 2C6–3C6) with age, often with an olive tint, unchanging when bruised. Pores 0.3–0.5 mm in diam., mostly subangular, slightly radially elongated around stipe at maturity, smaller near pileus margin, concolorous with tubes. Stipe 15–40 × 2–4 mm, central, cylindrical or narrowly clavate, solid, equal to slightly tender downwards, greyish-orange (6B4), greyish-red (7B4) to brownish-orange (6C4–7C4), without reticulation, smooth to faintly longitudinally striate, gelatinous or strongly viscid when young and wet, usually covered with a mucilaginous layer, with white basal mycelium. Odour not distinct. Taste mild.

Basidiospores [150/4/4] (9.5–)10–13.5 × (4–)4.5–5 µm, Q = (2.2–)2.3–2.5(–2.7), Qm = 2.48 ± 0.18, subfusiform and inequilateral in side view, oblong in ventral view, smooth, yellowish to yellowish-brown in 5% KOH and yellow brown to dark brown in Melzer’s reagent, thin-walled. Basidia 20–30 × 7–10 µm, clavate, 4-spored, sterigmata 2–4.5 µm long, yellowish-white to hyaline in 5% KOH, without basal clamps. Pleurocystidia 35–60 × 8–13 μm, fusiform, thin-walled. Cheilocystidia frequent, similar to pleurocystidia in shape and size. Hymenophoral trama composed of subparallel hyphae 4–10 μm broad, yellowish-white to hyaline in 5% KOH. Pileipellis an ixotrichodermium of erect hyphae 5–12 μm in diameter, branched, yellowish-white to hyaline in 5% KOH, dextrinoid in Melzer’s reagent; terminal cells 27–50 × 7–12 µm, cylindrical, clavate or nearly fusoid. Stipitipellis a layer of repent to suberect branching hyphae 3–6 μm in diam., hyaline in 5% KOH. Clamp connections absent in all tissues.

Ecology and distribution

Solitary or scattered on ground with humus and debris, usually growing amongst the mosses (Fissidens sp. and Pottiaceae sp.) under Fagaceae, mixed with other broadleaf trees, alt. 300–500 m; May to July, known from Guangdong and Anhui Province.

Additional specimens examined

China, Hunan Province, Chenzhou City, Rucheng Town, Jiulongjian National Forest Park, 8 May 2014, H. Huang (GDGM44476); Same location, 12 June 2015, M. Zhang (GDGM44733); Anhui Province, Huangshan City, Huangshan National Forest Park, 27 July 2015, C.H. Li (GDGM44821).

Notes

Phylogenetic analyses showed that A. glutinosus is closely related to A. marroninus, A. tenuis, A. thibetanus and A. viscidipes; however, the independent phylogenetic position and different morphological characters can distinguish A. glutinosus from these similar species. Aureoboletus marroninus differs in having a more wrinkled and darker (violet brown or maroon) pileus, white context and smaller basidiospores 8.5–10 × 4–4.5 µm (Zhang et al. 2014). Aureoboletus tenuis has relatively larger basidiomata (pileus up to 3.5 cm broad) usually lacking well-developed veil remnants on pileus margin, smaller basidiospores 11–12 × 4–5 μm and ixotrichodermial stipitipellis composed of terminal hyphae with swollen tips (Zhang et al. 2014). Aureoboletus thibetanus is readily separated by its more robust basidiomata (pileus up to 5 cm broad), white ridged reticulation on pileus surface, white stipe and yellowish granular encrustation on cystidia and only known from the temperate zone in southwest China (Patouillard 1895; Yang et al.2003; Klofac 2010). Aureoboletus viscidipes differs in having a brownish to brown pileus tinged with yellowish-white, a longer (up to 4 cm long) and nearly white stipe and a thick layer of a reflective pale-yellow substance on the surface of cheilocystidia and pleurocystidia (Wu et al. 2016).

Figure 2. 

Basidiomata of six new species and one new combination of Aureoboletus from China. A, B A. glutinosus (A GDGM44476 B GDGM44477, holotype) C A. griseorufescens (GDGM28490, holotype) D, E A. miniatoaurantiacus (D GDGM43439 E GDGM43282) F, G A. raphanaceus (F GDGM45911, holotype G GDGM52890) H, I A. sinobadius (H GDGM44732 I GDGM 71932, holotype) J, K A. solus (GDGM44759, holotype) L A. velutipes (L GDGM44713, holotype). Scale bars: 2 cm.

Figure 3. 

Scanning electron micrograph of basidiospores of six new species and one new combination of Aureoboletus from China. A A. glutinosus (GDGM44477, holotype) B A. griseorufescens (GDGM28490, holotype) C, D A. miniatoaurantiacus (C GDGM43439 D GDGM4855) E, F A. raphanaceus (GDGM45911, holotype) G A. sinobadius (GDGM71932, holotype) H A. solus (GDGM44759, holotype) I A. velutipes (GDGM44713, holotype). Scale bars: 5 µm.

Figure 4. 

Aureoboletus glutinosus. A Basidiospores B Cheilocystidia and pleurocystidia C Basidia and pleurocystidia D Pileipellis E Stipitipellis. Scale bars: 10 µm (A–C); 20 µm (D, E).

Aureoboletus griseorufescens Ming Zhang & T.H. Li, sp. nov.

MycoBank No: 827104
Figs 2C, 3B, 5A–E

Diagnosis

This taxon can be distinguished from other Aureoboletus species by its brownish-orange to ruby pileus colour, white to yellowish-white context changing to greyish-red or greyish-rose when exposed, light yellow tubes and comparatively small basidiospores 9–10.5 × 4.5–5 μm.

Etymology

griseorufescens” refers to the greyish-red discolouration of context when exposed or bruised.

Type

China, Guangdong Province, Shaoguan City, Chebaling National Natural Reserve, on soil under the broadleaf forest dominated by Fagaceae trees, alt. 300 m, 23°22'N, 113°42'E, 15 July 2008, C.Y. Deng (holotype: GDGM28490) .

Description

Basidiomata small to medium-sized. Pileus 2–5 cm wide, hemispheric when young, becoming convex to nearly plane in age, fleshy, subviscid or slightly viscid when wet, glabrous to minutely velvet-subtomentose, slightly wrinkled to rugulose, even or nearly so at margin, brownish-orange, brownish-red, dark red to greyish-ruby (6C6–7 to 11C6–7). Context 3–6 mm thick at centre, firm and tough, white to yellowish-white (2A1–2 to 3A1–2), more or less greyish-red (9C4–11C4) beneath the pileipellis and browner at the border line adjacent to tubes, gradually changing to greyish-red (9C4–11C4) to greyish-rose (12B5) when exposed. Tubes 2–4 mm deep, light yellow, yellow, pastel yellow to greenish-yellow (2A5, 3A4–6), unchanging when bruised. Pores small, 1–2 per mm, circular to angular, somewhat relatively larger and shallowly depressed around the stipe at maturity, concolorous with tubes, unchanging when bruised. Stipe 35–60 × 4–10 mm, central, cylindrical or clavate, equal to slightly enlarged downwards, smooth, viscid in wet condition, concolorous with pileus, pale in the apex. Stipe context white to reddish-white (9A2–11A2), gradually changing to greyish-red (9C4–11D5) to greyish-rose (12B5) when exposed, especially in the lower part. Basal mycelium white. Odour none. Taste mild.

Basidiospores [50/2/2] (8–)9–10.5(–11) × (4–)4.5–5(–5.5) μm, Q = (1.8–)2–2.2 (2.6), Qm = 2.19 ± 0.18, subfusiform and inequilateral in side view, oblong in ventral view, smooth, yellowish to yellowish-brown in 5% KOH and yellow brown to dark brown in Melzer’s reagent, thin-walled. Basidia 4-spored 25–30 × 7–11 μm, clavate, yellowish-white to hyaline in 5% KOH, sterigmata 2–3 μm. Cheilocystidia infrequent. Pleurocystidia 43–70 × 8–13 μm, fusiform, thin-walled, yellowish-white to hyaline in 5% KOH. Hymenophoral trama composed of subparallel hyphae 5–8 μm broad, yellowish-white to hyaline in 5% KOH. Pileipellis an entangled trichodermium of erect hyphae 12–19 μm in diameter, branched, yellowish-white to hyaline in 5% KOH, yellow brown to dark brown in Melzer’s reagent, terminal cells 20–50 × 6–10 μm, cylindrical, clavate or nearly fusoid. Stipitipellis a tangled layer of repent to suberect branching hyphae 7–10 μm in diam., hyaline in 5% KOH, with terminal cells 22–30 × 7–18 μm. Caulocystidia 43–58 × 12–18 μm, numerous, in clusters, clavate, fusoid or fusoid ventricose, mostly clavate, swollen at apex and usually contain yellow to yellowish-brown substance at an early stage in 5% KOH. Clamp connections absent in all tissues.

Ecology and distribution

Solitary or scattered on ground with humus and debris under Fagaceae trees, mixed with other broadleaf trees, alt. 200–400 m; June to September; currently only known from southern China.

Additional specimens examined

China, Hainan Province, Changjiang County, Bawangling National Forest Park, 7 July 2013, M. Zhang (ZhangM131).

Notes

Aureoboletus griseorufescens is somewhat similar to the recently reported species A. venustus from southern China; however, the latter taxon differs in having relatively larger (pileus up to 8 cm) and more viscous basidiomata, a reddish-orange pileus and broader basidiospores 7.5–10.5 × 5–6 μm (Li et al. 2016). In addition, A. griseorufescens formed a separate species level branch at the base of the phylogenetic tree (Fig. 1), indicating that it is in an independent phylogenetic position.

Figure 5. 

Aureoboletus griseorufescens. A Basidia and pleurocystidia B Cheilocystidia and pleurocystidia C Basidiospores D Pileipellis E Stipitipellis. Scale bars: 10 µm (A–C); 20 µm (D, E).

Aureoboletus raphanaceus Ming Zhang & T.H. Li, sp. nov.

MycoBank No: 827106
Figs 2F, G, 3E, F, 6A–E

Diagnosis

This species can be easily distinguished from other Aureoboletus taxa by its dry and yellowish-white to pinkish-white pileus covered with fibrillose to tomentose squamules, radish smell and ovoid basidiospores 7.5–9 × 5–6 μm.

Etymology

raphanaceus” refers to the radish smell of the new species.

Type

China, Jiangxi Province, Chongyi Town, Yangling National Forest Park, on soil under the broadleaf forest dominated by Fagaceae trees, at 25°28'N, 114°19'E, alt. 300 m, 1 September 2016, H. Huang (holotype: GDGM45911).

Description

Basidiomata small to medium-sized. Pileus 3–8 cm wide, hemispheric when young, becoming convex to nearly plane in age, fleshy, dry or slightly viscid when wet, covered with greenish-grey, yellowish-grey to brownish-grey (1D2–10D2) fibrillose to tomentose squamules on yellowish-white (1A2–4A2) to pinkish-white background, slightly wrinkled at disc; margin thin, slightly incurved at first, then extending. Context 8–12 mm thick at centre, firm and tough in youth, becoming soft, white, more or less pinkish, brownish-orange (5C4–7C4), greyish-red (8C4–10C4) to light brown (5D4–7D4) beneath the pileipellis, unchanging or slightly changing blue near the hymenophore when exposed. Tubes 4–7 mm deep, greyish-yellow (1B5–3B5), light yellow (1A5–3A5) to yellow (2A7–3A7), unchanging when bruised. Pores small, 0.5–1 per mm, circular to angular, somewhat relatively larger and shallowly depressed around the stipe at maturity; pore-surface concolorous with tubes, unchanging when hurt. Stipe 20–40 × 8–15 mm, central, cylindrical or clavate, equal to slightly enlarged downwards, dry, concolorous with pileus, longitudinally streaked and faintly pruinose or tomentose, with a very pale flush of pastel red (8A5–10A5) zone at apex. Stipe context white to yellowish-white, slightly changing pale yellow (2A3–4A3) when exposed, especially in the lower part. Basal mycelium white. Odour as radish. Taste mild.

Basidiospores [80/3/3] (7–)7.5–9(–10) × 5–6 μm, Q= (1.27–)1.45–1.6(–1.7), Qm = 1.51 ± 0.08, ovoid and inequilateral in side view, ovoid in ventral view, smooth, yellowish to pale brown in 5% KOH and yellowish-brown in Melzer’s reagent, thin-walled. Basidia 20–30 × 8–11 μm, clavate, 4-spored, rarely 1-, 2-, 3-spored, yellowish-white to hyaline in 5% KOH, without basal clamps, sterigmata 2–3.5 µm long. Pleurocystidia 30–60 × 8–13 μm, fusiform, thin-walled, usually containing golden-yellow contents at first, gradually changing yellowish-white to hyaline in 5% KOH. Cheilocystidia infrequent, similar to pleurocystidia in shape and size. Hymenophoral trama composed of subparallel hyphae 5–23 μm broad, yellowish-white to hyaline in 5% KOH. Pileipellis an ixotrichodermium to trichodermium of erect hyphae 4–12 μm in diameter, usually covered with yellow to brownish-yellow pigment slightly dissolving in 5% KOH, branched, yellowish-white to hyaline in 5% KOH, dextrinoid in Melzer’s reagent; terminal cells cylindrical, clavate or nearly fusoid. Stipitipellis a layer of suberect branching hyphae 4–15 μm in diameter, hyaline in 5% KOH. Caulocystidia 30–60 × 8–12 μm, numerous, in clusters, fusiform to lageniform and usually contain yellow to yellowish-brown substance in an early stage in 5% KOH. Clamp connections absent in all tissues.

Ecology and distribution

Solitary or scattered on ground with humus and debris under Fagaceae trees mixed with other broadleaf trees, alt. 300–1300 m; June to September; Currently known from Jiangxi and Hunan Province.

Additional specimens examined

China, Jiangxi Province, Chongyi County, Yangling National Forest Park, alt. 550 m, 1 September 2016, M. Zhang (GDGM52908); Same locality and date B. Song (GDGM53127), M. Zhang (GDGM52266 and GDGM50266), H Huang (GDGM52890); Hunan Province, Guidong Town, Bamianshan National Nature Reserve, alt. 1250 m, 18 June 2016, Z.P. Song (GDGM52543 and GDGM46333).

Notes

The yellowish-white basidioma colour makes it easy to distinguish A. raphanaceus from the other species. Boletus orientialbus N.K. Zeng & Zhu L. Yang recently described from China is somewhat similar to A. raphanaceus in colour; however, B. orientialbus differs in having more robust basidiomata, smooth pileus, reticulate stipe and smaller basidiospores 7–10 × 4.5– 5 μm (Zeng et al. 2013).

Figure 6. 

Aureoboletus raphanaceus. A Basidiospores B Basidia and pleurocystidia C pleurocystidia D Pileipellis E Stipitipellis. Scale bars: 10 µm (A–C), 20 µm (D, E).

Aureoboletus sinobadius Ming Zhang & T.H. Li, sp. nov.

MycoBank No: 827101
Figs 2H, I, 3G, 7A–F

Diagnosis

This species is distinguished from other Aureoboletus species by its pastel red to reddish-brown pileus, light yellow hymenophore unchanging when bruised, salty taste and two different shapes of basidiospores.

Etymology

sino-” refers China, the holotype’s location of the species; “badius” means the brownish-red or chestnut pileus colour.

Type

China, Guangdong Province, Guangzhou City, Baiyun Mountain Scenic Area, on soil and usually growing amongst moss under broadleaf forest, dominated by Fagaceae trees, alt. 280 m, 18 May 2018, M. Zhang (holotype: GDGM71932).

Description

Basidiomata medium to large-sized. Pileus 5–10 cm wide, hemispheric when young, becoming convex to nearly plane in age, fleshy, viscid, especially when young and wet, glabrous to minutely velvet-subtomentose, slightly wrinkled, usually violet brown (10E5–8 to 12E5–8) when young, gradually fading to pastel red (8A5–10A5), brownish-red (9C7–10C7), reddish-brown to brownish-violet (9D6–11D6, 9D7–11D7) at maturity, with a thin and slightly incurved margin. Context 7–10 mm thick at centre, firm and tough in youth and later soft, white to yellowish-white, and more or less greyish-red (9C4–10C4) beneath the pileipellis, slightly changing to greyish-red (9C4–10D5) when exposed. Tubes 8–15 mm deep, light yellow to greenish-yellow (2A5, 2B5), unchanging when bruised. Pores small, 1–1.5 per mm, circular to angular, somewhat relatively larger and shallowly depressed around the stipe at maturity, unchanging when bruised; pore-surface concolorous with tubes. Stipe 40–80 × 5–9 mm, central, cylindrical or clavate, equal to slightly enlarged downwards, smooth, viscid when wet, pastel red (8A5–10A5), with a very pale flush of pale orange (5A3–6A3) fibrous stripe. Stipe context white to yellowish-white, slightly changing to greyish-red (9C4–10D5) when bruised. Basal mycelium white. Odour mild. Taste salty.

Basidiospores [150/8/5] 10–13(–14) × (4–) 4.5–5 (–5.5) μm, average 11.5–12.5 × 4.5–5, Q = (–2) 2.3–2.67 (–2.88), Qm = 2.44 ± 0.22, subfusiform and inequilateral in side view with an obtuse apex, oblong to ovoid in ventral view, smooth, yellowish to yellowish-brown in 5% KOH, yellow brown to dark brown in Melzer’s reagent, occasionally two different shapes in some specimens. Basidia 22–33 × 8–11 μm, clavate, predominantly 4-spored, partially 2-spored, with sterigmata 2–4 µm long, yellowish-white to hyaline in 5% KOH, without basal clamp. Pleurocystidia 27–50 × 7–13 μm, fusiform, thin-walled, usually containing golden-yellow contents at first, gradually changing from yellowish-white to hyaline in 5% KOH. Cheilocystidia frequent, 23–48 × 9–15 μm, clavate to subfusiform, thin-walled, containing golden-yellow contents at first, gradually changing yellowish-white to hyaline in 5% KOH. Hymenophoral trama composed of subparallel hyphae 4–10 μm broad, yellowish-white to hyaline in 5% KOH. Pileipellis an ixotrichodermium of erect and branched hyphae 6–12 μm in diameter, yellowish-white to hyaline in 5% KOH, dextrinoid in Melzer’s reagent; terminal cells 35–60 × 5–10 μm, cylindrical, clavate or nearly fusoid. Stipitipellis a layer of repent to suberect branched hyphae 3–10 μm in diam., hyaline in 5% KOH. Caulocystidia 30–45 × 9–18 μm, mostly swollen clavate, usually containing yellow to yellowish-brown substance at an early stage in 5% KOH. Clamp connections absent in all tissues.

Ecology and distribution

Solitary or scattered on ground with humus and debris under Castanopsis fissa Rehder E.H. Wilson mixed with other broadleaf trees, alt. 200–300 m; known from south China.

Additional specimens examined

China, Guangdong Province, Guangzhou City, Baiyun Mountain Scenic Area, alt. 300 m, 4 June 2015, M. Zhang (GDGM44736 and GDGM44732); Same location, alt. 300 m, 30 May 2013, M. Zhang (GDGM43275); Same location, alt. 300 m, 4 June 2013, M. Zhang (ZhangM55); Same location, alt. 280 m, 14 May 2015, M. Zhang (GDGM45920); Guangdong Province, Huizhou City, Xiangtoushan National Nature Reserve, alt. 300 m, 2 April 2015, M. Zhang (GDGM44473); Hunan Province, Chenzhou City, Jiulongjiang National Forest Park, alt. 280 m, 13 June 2015, M. Zhang (GDGM44730); Guangzhou City, Research Institute of Tropical Forestry, alt. 200 m, 4 May 2018, J. Xu (GDGM72253).

Notes

Aureoboletus sinobadius is morphologically similar to A. auriporus, A. flaviporus (Earle) Klofac, A. gentilis, A. novoguineensis and A. venustus. However, A. auriporus differs from A. sinobadius in the pinkish cinnamon, vinaceous to vinaceous brown pileus, longer and more robust stipe covered with yellow pruina or floccosity at apex, slight acid taste and broader basidiospores 11–16 × 4–6 μm (Pouzar 1957; Smith and Thiers 1971; Halling 1989; Both 1993; Bessette et al. 2000; Klofac 2010); A. flaviporus differs in the pale cinnamon to dark reddish-brown pileus, reddish-brown stipe usually with reticulation at the apex, acidic taste, broader basidiospores 11–15 × 4–6 μm and the known distribution in North America (Bessette et al. 2000); A. gentilis, originally described from Europe, differs in having pinkish-brown to flesh-coloured pileus, whitish context unchanging when exposed and longer and broader basidiospores 12–15 × 5–6.5 μm (Singer 1945; Pouzar 1957; Klofac 2010); A. novoguineensis, originally described from New Guinea, has pale pink brown or pale red context, shorter (3–4 mm deep) and sometimes compound hymenophore, acid taste and larger basidiospores (11.5–15.5 × 4.5–5.5 μm) and pleurocystidia (36–66 × 13–18 μm) (Hongo 1973); A. venustus recently described from southern China differs by its shorter and broader basidiospores 7.5–10.5 × 5–6 μm (Li et al. 2016).

Figure 7. 

Aureoboletus sinobadius. A Basidiospores B Cheilocystidia and pleurocystidia C Basidia and pleurocystidia D Pileipellis E Stipitipellis. Scale bars: 10 µm (A–C); 20 µm (D, E).

Aureoboletus solus Ming Zhang & T.H. Li, sp. nov.

MycoBank No: 827105
Figs 2, K, 3H, 8A–D

Diagnosis

This species can be easily distinguished from other Aureoboletus taxa by its dry and small basidiomata, brownish-yellow to greyish-red pileus, glabrous stipe and smaller basidiospores (7–)8–10.5(–11) × (4–)4.5–5 μm.

Etymology

solus” refers to the solitary habit.

Type

China, Guangdong Province, Shaoguan City, Nanling National Nature Reserve, on soil under the broadleaf forest, dominated by Fagaceae trees, 16 June 2015, M. Zhang (holotype: GDGM44759).

Description

Basidiomata small-sized. Pileus 1.5–2.5 cm wide, hemispheric when young, becoming convex to nearly plane in age, fleshy, dry or slightly viscid when wet, minutely velvet subtomentose, slightly wrinkled, brownish-yellow, brownish-orange, brownish-red to greyish-red (5C7–8C7, 5C5–9C5); margin thin, slightly incurved at first, becoming nearly straight, often appendiculate with small membranous remains of the veil. Context 2–6 mm thick at centre, firm and tough in youth, becoming soft, white, more or less greyish-red (9C5–11C5) to brownish-red (9C7–11C7) beneath the pileipellis, unchanging when exposed. Tubes 2–3 mm deep, gr-yish-yellow (1B5–3B5), light yellow (1A5–3A5) to vivid yellow (1A8–3A8), gradually changing to greenish-yellow when mature, unchanging when bruised, shallowly depressed around the stipe at maturity. Pores small, 1–2 per mm, somewhat larger around the stipe, circular to angular; pore-surface concolorous with tubes. Stipe 20–45 × 2–6 mm, central, cylindrical or clavate, equal to slightly enlarged downwards, glabrous, dry or slightly viscid when wet, pale orange to pale red (5A3–7A3), pastel red (8A5–10A5), with very pale flush of pastel red (8A5–10A5) fibrous stripes. Stipe context white to pastel red (8A4–10A4), slightly darker when bruised, especially in the lower part. Basal mycelium white. Odour none. Taste mild.

Basidiospores [80/3/3] (7–)8–10.5(–11) ×(4–)4.5–5 μm, Q = (1.5–)1.8–2.2(–2.6), Qm = 2.0 ± 0.21, subfusiform and inequilateral in side view, oblong to ovoid in ventral view, smooth, yellowish to yellowish-brown in 5% KOH and yellow brown to dark brown in Melzer’s reagent, thin-walled. Basidia 1, 2, 4-spored 25–46 × 9–16 μm, clavate, yellowish-white to hyaline in 5% KOH; sterigmata 2–4.5 µm long. Pleurocystidia frequent, 38–66 × 11–15 μm, fusiform, thin-walled, yellowish-white to hyaline in 5% KOH. Cheilocystidia similar to pleurocystidia in shape and size. Hymenophoral trama composed of subparallel hyphae 5–11 μm broad, yellowish-white to hyaline in 5% KOH. Pileipellis an entangled trichodermium of erect hyphae 5–17 μm in diameter, branched, yellowish-white to hyaline in 5% KOH, dextrinoid in Melzer’s reagent; terminal cells cylindrical, clavate or nearly fusoid. Stipitipellis a layer of repent hyphae 4–23 μm in diameter, hyaline in 5% KOH. Caulocystidia infrequent. Clamp connections absent in all tissues.

Ecology and distribution

Solitary or gregarious on soil under broadleaf forests dominated by Castanopsis spp. and Cyclobalanopsis spp. and mixed with other broadleaf trees, alt. 300–1200 m; May to July, currently only known from Guangdong Province.

Additional specimens examined

China, Guangdong Province, Shaoguan City, Nangling National Nature Reserve, alt. 1200 m, 29 July 2017, M. Zhang (GDGM70342); Guangdong Province, Huizhou County, Xiangtoushan National Nature Reserve, alt. 400 m, 16 June 2016, J.P. Zou (GDGM46222); Guangdong Province, Huizhou City, Nankunshan Provincial Nature Reserve, alt. 700 m, 15 May 2013, M. Zhang (GDGM42822); Guangdong Province, Shaoguan City, Danxianshan National Nature Reserve, alt. 300 m, 3 June 2017, M. Zhang (GDGM46807), Same locality, 2 June 2017, M. Zhang (GDGM49404).

Notes

Aureoboletus solus looks like A. tenuis; however, the latter differs from the former in its viscid basidiomata, ixotrichodermial stipitipellis, composed of terminal hyphae with slightly swollen tips and larger basidiospores (10–)11–12 × 4–5 µm (Zhang et al. 2014). Phylogenetic analyses indicated that A. solus is closely related to A. nephrosporus, but A. nephrosporus differs in having larger basidiomata with a red to brownish-red pileus, ovoid to nephroid basidiospores 8–10.5 × 5–6 µm and cheilocystidia and pleurocystidia covered with a thick layer of a strongly refractive pale yellow substance (Wu et al. 2016).

Figure 8. 

Aureoboletus solus. A Basidiospores B Cheilocystidia and pleurocystidia C Basidia and pleurocystidia D Pileipellis. Scale bars: 10 µm (A–D).

Aureoboletus velutipes Ming Zhang & T.H. Li, sp. nov.

MycoBank No: 827108
Figs 2L, 3I, 9A–E

Diagnosis

This species can be easily distinguished from others in Aureoboletus by its dry and small basidiomata, brown orange to reddish-brown pileus, light yellow to pastel yellow stipe, covered with fibrillose to tomentose squamules and smooth basidiospores 10–13 × 4–6.5 μm.

Etymology

velutipes” refers to the stipe, covered with fibrillose to tomentose squamules.

Type

China, Guangdong Province, Huizhou City, Xiangtoushan National Nature Reserve, on soil under the broadleaf forest, dominated by Fagaceae trees, alt. 350 m, 2 April 2015, M. Zhang (holotype: GDGM44713).

Basidiomata small-sized. Pileus 2–4 cm wide, obtuse to convex when young, becoming broadly convex to plane at mature, fleshy, dry, covered with fibrillose to tomentose squamules, light yellow, light orange (4A4–6A4), brownish-orange (6C7–7C7), brown to reddish-brown (6D7–9D7), slightly fading to light orange to brownish-orange towards margin. Context 3–5 mm thick at stipe, firm and tough in youth, soft when matured, yellowish to white on the whole, more or less reddish-brown beneath the pileipellis, slightly changing to pastel red (7A4–9A4) when exposed. Tubes 3–5 mm deep, distinctly depressed around stipe, yellowish-white (2A2–4A2) when young, becoming pale yellow, greyish-yellow, pastel yellow to olive yellow (2A3–4A3, 1B3–2B3, 2A4–3A4, 2C6–3C6) in age, often with an olive tint, unchanging when bruised. Pores 0.5–0.8 mm in diam., mostly subangular, slightly elongated around stipe at maturity, smaller near pileus margin, concolorous with tubes. Stipe 30–60 × 5–10 mm, central, cylindrical or narrowly clavate, solid, equal to slightly enlarged downwards, covered with white, yellowish-white to yellowish-brown fibrillose to tomentose squamules, usually forming reticulation or longitudinally striate, light yellow to pastel yellow (2A4–4A4, 2A5–4A5), with white basal mycelium. Odour none. Taste mild.

Basidiospores [90/3/3] 10–13 × (4–)5–6(–6.5) μm, Q = (1.75–)1.8–2.2(–2.4), Qm = 2.08 ± 0.35, subfusiform and inequilateral in side view, oblong to ovoid in ventral view, smooth, yellowish to yellowish-brown in 5% KOH and yellow brown to dark brown in Melzer’s reagent, thin-walled. Basidia 25–30 × 9–13 μm, clavate, predominantly 4-spored but frequently also 2-spored, with sterigmata 2–3 µm long, yellowish-white to hyaline in 5% KOH, without basal clamps. Pleurocystidia 35–65 × 10–18 μm, fusiform, thin-walled. Cheilocystidia frequent, similar to pleurocystidia in shape and size. Hymenophoral trama composed of subparallel hyphae 6–10 μm broad, yellowish-white to hyaline in 5% KOH. Pileipellis a trichodermium of erect and often branched hyphae 4–17 μm in diameter, yellowish-white to hyaline in 5% KOH, dextrinoid in Melzer’s reagent; terminal cells 30–60 × 4–17 μm, cylindrical, clavate or nearly fusoid. Stipitipellis a layer of repent to suberect branching hyphae 3–15 μm in diameter, with swollen tips, terminal cells 30–70 × 11–21 μm, hyaline in 5% KOH. Clamp connections absent in all tissues.

Ecology and distribution

Scattered on soil in subtropical forests, dominated by Fagaceae (Castanopsis spp., Lithocarpus spp. and Quercus spp., etc). Currently known from southern China.

Additional specimens examined

China, Guangxi Province, Guilin City, Maoershan National Nature Reserve, alt. 1380 m, 1 July 2012, M. Zhang (GDGM42608); Jiangxi Province, Jinggangshan City, Jingganshan National Nature Reserve, alt. 1000 m, 21 June 2016, H. Huang (GDGM52409).

Notes

The obviously villose or fibrous squamulose stipe can distinguish it from other species in Aureoboletus. Aureoboletus catenarius, recently described from southwest China, is somewhat similar to A. velutipes with a dry and tomentose pileus, but A. catenarius has a cracked and light brown to reddish-brown pileus, faintly or finely fibrillose stipe and smaller basidiospores 7–9 × 3.5–5 μm (Wu et al. 2016).

Figure 9. 

Aureoboletus velutipes. A Basidiospores B Pleurocystidia C Basidia and pleurocystidia D Pileipellis E Stipitipellis. Scale bars: 10 µm (A–C), 40 µm (D, E).

Aureoboletus miniatoaurantiacus (Bi & Loh) Ming Zhang, N.K. Zeng & T.H. Li, comb. nov.

MycoBank No: 827109
Figs 2D, E, 3C, D, 10A–D

Basionym

Boletus miniatoaurantiacus C.S. Bi & Loh, in Bi, Loh & Zheng, Acta Bot. Yunn. 4(1): 60, 1982

Synonym

Aureoboletus tomentosus G. Wu & Zhu L. Yang, in Wu, Li, Zhu, Zhao, Han, Cui, Li, Xu & Yang, Fungal Diversity 81: 51, 2016

Diagnosis

In Bi et al. (1982): Pileus 1–1.6 cm latus, siccus, obtuse hemisphaerius, aurantiacus, confertim et minute villoso-tomentosus. Contexto flava, immutibili, ad stipitem 2–3 cm crasso, sapor mitis et odor nullus. Stipes centralis, 3–3.3 cm longus, 3–6 mm crassus, albidus, in parte in feriore flavus, subcylindraceus, solidus, velutinus. Tubuli albidi, immutabiles, ad stipitem breviter decurrentes, 3 mm longi, facile denudati; pori ovati, majuscules, 3 mm diam. Sporae ellipsoideae, laeves, pallido-flavae, 7–10 × 3.3–4 μm, 1 guttatae. Pleurocystidiis 35 × 6.5 μm, paucis.

Basidiomata small to medium-sized. Pileus 1.5–8 cm wide, hemispheric when young, becoming convex to nearly plane in age, fleshy, dry or viscid when wet, surface minutely tomentose or pulverous, slightly wrinkled, orange yellow, reddish-yellow, orange to reddish-orange (4A6–7A6, 4A7–7A7), commonly with a thin and slightly extended margin. Context 5–10 mm thick at centre, firm and tough in youth and, later, soft, white to yellowish-white, with more or less green tint at border contacting tubes, unchanging when exposed. Tube 3–10 mm deep, light orange to orange unchanging when bruised. Pores polygonal, 0.5–1.5 per mm, somewhat relatively larger and shallowly depressed around the stipe, orange to pale orange unchanging when bruised. Stipe 30–80 × 4–10 mm, central, solid, cylindrical or clavate, equal to slightly enlarged downwards, smooth to distinctly longitudinally streaks or broad reticulations, viscid in wet condition, concolorous with pileus. Stipe context concolorous with that of pileus, unchanging when exposed. Basal mycelium white to yellowish-white. Odour strong. Taste mild.

Basidiospores [90/3/3] (6.5–)7–10.5(–11) × (4–)4.5–5.5(–6) μm, Q = (1.42–)1.6–2.0(–2.3), Qm = 1.79 ± 0.18, ovoid and inequilateral in side view with an obtuse apex, ovoid in ventral view, smooth, yellowish to yellowish-brown in 5% KOH and yellow brown to dark brown in Melzer’s reagent, thin-walled. Basidia 18–35 (45) × 7–14 μm, 4-spored, rarely 1-, 2-, 3-spored, clavate, yellowish-white to hyaline in 5% KOH, sterigmata 2–3 μm. Cheilocystidia (21) 26–55 (61) × (6) 8–12 μm, fusiform to subclavate, thin-walled, contained with bright yellow pigments. Pleurocystidia similar to cheilocystidia in shape and size, thin-walled, yellowish-white to hyaline in 5% KOH. Hymenophoral trama composed of interwoven branched hyphae 6–15 μm wide, yellowish-white to hyaline in 5% KOH. Pileipellis an entangled trichodermium to ixotrichodermium of erect hyphae 4–18 μm in diameter, composed of yellow to bright yellow vacuolar pigmented filamentous hyphae, terminal cells cylindrical, clavate or nearly fusoid. Stipitipellis a tangled layer of repent to suberect branching hyphae 7–12 μm in diameter, hyaline in 5% KOH. Caulocystidia 25–75 × 12–18 μm, common, clavate, fusoid or fusoid ventricose and usually contain yellow to yellowish-brown substance in an early stage in 5% KOH. Stipe trama composed of parallel hyphae 4–18 μm wide. Clamp connections absent in all tissues.

Ecology and distribution

Scattered on soil in tropical to subtropical forests dominated by Fagaceae (Castanopsis chinensis, C. fissa, Lithocarpus spp. and Quercus spp.). Currently known from southern and southwest China

Additional specimens examined

China, Guangdong Province, Zhaoqing City, Dinghu Mountain, 6 September 1980, C.S. Bi et al. 677 (GDGM4677, holotype of B. miniatoaurantiacus); Same locality, 14 April 1981, C. Li (GDGM5071); 11 August 1981, C.S. Bi et al. 855 (GDGM4855); Fujian Province, Zhangping City, alt. 350 m, 2 September 2009, N.K. Zeng 664, 669 (FHMU424, 429); same locality, 27 July 2013, N.K. Zeng 1294 (FHMU848); 29 July 2013, N.K. Zeng 1323 (FHMU876); 1 August 2013, N.K. Zeng 1339 (FHMU891); Guangdong Province, Guangzhou City, Tianluhu Forest Park, alt. 200 m, 29 May 2015, M. Zhang (GDGM42855); Guangdong Province, Shaoguan City, Chebaling National Nature Reserve, alt. 300 m, 3 September 2013, M. Zhang & C.Q. Wang (GDGM43282); Guangdong Province, Huizhou City, Xiangtoushan National Nature Reserve, alt. 300 m, 7 July 2015, M. Zhang (GDGM44727); Jiangxi Province, Chongyi County, Yangling National Forest Park, alt. 280 m, 14 August 2015, M. Zhang (GDGM51694 and GDGM43439); same locality, 31 August 2016, H. Huang (GDGM52888); Same locality, 1 September 2016, M. Zhang (GDGM53350); Same locality, 2 September 2016, M. Zhang (GDGM53274); Same locality, 3 September 2016, M. Zhang (GDGM53501).

Notes

Aureoboletus miniatoaurantiacus, originally described as B. miniatoaurantiacus, is a rather common species in southern China and can be easily distinguished by its bright orange-yellow basidiomata, tomentose or pulverulent pileus surface, light orange to orange hymenophore unchanging when bruised and ovoid basidiospores. Based on a re-study of the type specimen and other collections quoted by Bi et al. in 1994, we found that the type specimen is composed of two small immature basidiomata, which are in a poor condition for morphological observation, but other voucher specimens fit well with the description of A. tomentosus. Thus, the newly described species A. tomentosus is, in fact, a synonym of A. miniatoaurantiacus, this conclusion also being supported by molecular data in this study (Bi et al. 1982; Bi et al. 1994; Wu et al. 2016). Aureoboletus auriflammeus, originally described from North America, is similar to A. miniatoaurantiacus; however, the former differs in having a distinctly reticulate stipe and narrower basidiospores (8–12 × 3–5 μm) (Murrill 1908; Bessette et al. 2000).

Figure 10. 

Aureoboletus miniatoaurantiacus. A Basidiospores B Cheilocystidia C Pleurocystidia D Basidia and pleurocystidia E Pileipellis. Scale bars: 10 µm (A–D), 20 µm (E).

Key to the species of Aureoboletus known in China

1 Pileus dry or slightly viscid when wet 2
Pileus viscid 13
2 Basidiomata medium to larger (≥ 6 cm in diam.) 3
Basidiomata smaller (< 6 cm in diam.) 4
3 Pileus 6–10 cm in diameter, greyish-orange to brownish-orange; stipe glabrous, greyish-yellow on the upper part to blond on the lower part; context unchanging when cut; basidiospores 9–11 × 4–5.5 µm A. yunnanensis
Pileus 6–15 cm in diameter, brownish-red to reddish-brown; context yellowish-white changing to yellowish-olivaceous when injured; hymenophore pale yellow to olivaceous yellow; stipe surface with longitudinal stripe, brownish-red to reddish-brown; basidiospores subglobose, 7–8 × 5.5–6 µm A. clavatus
4 Stipe surface smooth or with small dots or splotches 5
Stipe surface non-smooth, with reticula, longitudinal stripe, flocci or others 11
5 Basidiospores nodulose to verrucose, 12–15 × 8–11 µm; basidiomata small, golden brown to umber; stipe up to 7 cm long A. shichianus
Basidiospores surface smooth; other characters not as above 6
6 Hymenophore bright yellow to vivid yellow, unchanging when old 7
Hymenophore pale yellow, light yellow, greenish-yellow to olive brown 8
7 Pileus greyish-rose to brownish-red, glabrous to slightly subtomentose; context pale yellow to light yellow unchanging when cut; stipe dark orange to yellow ochre, with distinct longitudinal streaks and furfuraceous scales; basidiospores 8–10.5 × 5–6 µm A. nephrosporus
Pileus reddish-brown to greyish-ruby, smooth to minutely velvet-subtomentose; context white to yellowish-white changing to greyish-red to greyish-rose when exposed; stipe smooth, concolorous with pileus; stipe context white to reddish-white gradually changing to greyish-red to greyish-rose when bruised; basidiospores 9–10.5 × 4.5–5 μm A. griseorufescens
8 Pileus yellowish-white to reddish-white; context white, unchanging or slightly changing blue near the hymenium when exposed; tubes greyish-yellow to light yellow, unchanging when bruised; stipe context white to yellowish-white, slightly changing pale yellow when exposed; odour with radish scent; basidiospores 5–9 × 5–6 μm A. raphanaceus
Pileus coloured with brownish-red to reddish-brown tonalities 9
9 Pileipellis epithelium; basidiospores subfusoid, 7–9 × 3.5–5 μm A. catenarius
Pileipellis trichoderm 10
10 Basidiospores fusiform to ovoid, 8–10.5 × 4.5–5 μm A. solus
Basidiospores oblong to ovoid, 8.5–10.5 × 5–5.5 µm A. rubellus
11 Stipe surface ornamented with distinctly reticulation, pileus surface covered with coarse tomentose, basidiospores (20–)22–27(–28) × 9–13 µm A. mirabilis
Stipe surface without reticulation or the reticulation inconspicuous 12
12 Stipe surface ornamented with distinctly longitudinally streaks or dotted scales; pileus surface orange yellow, reddish-yellow to reddish-orange, covered with tomentose; hymenophore light orange to orange; basidiospores 7–11 × 4.5–6 μm A. miniatoaurantiacus
Stipe surface covered with distinctly fibrillose to tomentose squamules; pileus surface brownish-orange to reddish-brown, covered with fibrillose to tomentose squamules; context yellowish-white changing to pastel red when exposed; basidiospores 10–13 × 4–6.5 μm A. velutipes
13 Pileus margin with a gelatinised membranous veil 14
Pileus margin without any membranous veil 19
14 Pileus surface distinctly reticulate, coarsely rugose, chestnut-brown to pale brown; stipe whitish; pleurocystidia covered with yellow substance on surface; basidiospores 9.5–13 × 4.5–5 µm A. thibetanus
Pileus glabrous or slightly rugose in central 15
15 Basidiospores smooth 16
Basidiospores longitudinally costate, 12–16 × 9–12 µm A. longicollis
16 Pileus brownish to brown; basidiospores 10–12.5 × 4.5–5 µm A. viscidipes
Pileus reddish-brown to violet brown 17
17 Basidiomata usually ≥ 2.5 cm; basidiospores 11–13.5 × 4.5–5.5 µm A. tenuis
Basidiomata usually < 2.5 cm 18
18 Basidiospores 8.5–10 × 4–4.5 µm A. marroninus
Basidiospores 10–13.5 × 4.5–5 µm A. glutinosus
19 Pileus wrinkled, greyish-yellow to brownish-orange; taste salty; distribution in subalpine zone, ectomycorrhizal with Quercus spinose; basidiospores 15–21 × 5–6.5 μm A. squercus-spinosae
Pileus smooth, fibrillose to tomentose; the rest of the characters usually not as above 20
20 Basidiospores relatively broader, 7.5–10.5 × 5–6 μm, Qm < 2 A. venustus
Basidiospores relatively narrower, usually Qm ≥ 2 21
21 Basidiospores comparatively larger, 15–16.5 × 4.5–5 μm A. formosus
Basidiospores comparatively smaller, commonly < 15 μm long 22
22 Basidiomata small to medium-sized (pileus usually < 5 cm). Pileus yellowish-brown or reddish-golden, subtomentose; stipe light brown to brownish-orange; basidiospores 9–11 × 4–5 μm A. zangii
Basidiomata medium to large (pileus usually > 5 cm) 23
23 Pileus violet brown to brownish-violet, glabrous to minutely velvet-subtomentose; stipe pastel red with a pale flush fibrous stripe; taste salty; basidiospores 10–14 × 4.5–5.5 μm A. sinobadius
Pileus reddish-brown to brownish-red, nearly glabrous; stipe reddish-orange to garnet brown with faintly longitudinal streaks; taste unknown, basidiospores 8.5–13 × 4.5–5.5 μm A. duplicatoporus

Discussion

Species delimitation, species diversity and new taxa in China

In the taxonomic circumscription of the genus Aureoboletus proposed by Pouzar (1957), 35 species were identified prior to this study, of which 20 species were recorded from China (i.e. A. auriporus, A. catenarius, A. clavatus, A. duplicatoporus, A. formosus, A. longicollis, A. marroninus, A. mirabilis, A. nephrosporus, A. quercus-spinosae, A. rubellus, A. shichianus, A. tenuis, A. thibetanus, A. tomentosus, A. venustus, A. viscidipes, A. viscosus, A. yunnanensis and A. zangii). However, the report of the North American species A. auriporus was excluded from China in this study due to a misidentification, as its correct name is A. sinobadius. The previously described species, A. tomentosus, was proven to be A. miniatoaurantiacus and so, a new combination is proposed here. Six species, A. glutinosus, A. griseorufescens, A. sinobadius, A. solus, A. raphanaceus and A. velutipes, obtained from China, are newly described in this study.

The present study demonstrates that species of Aureoboletus are very diverse in China, especially in its southern areas. Common morphological characteristics and molecular data make Aureoboletus easily distinguishable from other existing genera in Boletaceae, but some variable morphological features make it difficult to recognise some species. Careful examination showed that several morphological characteristics are available to delimit these species in China. For example, the colour of the hymenophore and pattern of the pileus are important characteristics: A. glutinosus has a light yellow to olive yellow hymenophore and a coarse pileus with irregular reticulation; A. sinobadius has a vivid yellow hymenophore and a subtomentose to glabrous and viscid pileus; A. miniatoaurantiacus has a light orange to orange hymenophore and a tomentose to pulverous pileus; regarding the size of basidiomata, A. clavatus and A. yunnanensis have relatively larger basidiomata up to 10 cm in diameter, whereas A. glutinosus and A. marroninus have smaller basidiomata usually less than 2.5 cm in diameter. The colour of the pileus and the colour and odour of the context also help to identify species in the field. In contrast to macro-morphology, several micro-morphological features can also be used to discriminate species of Aureoboletus, such as the size and shape of basidiospores and the shape and inclusion of cystidia, pileipellis and stipitipellis seem to be rather constant amongst the different species.

Phylogenetic analyses supported the presence of eight clades in Aureoboletus

In the present study, all selected samples of Aureoboletus formed a well-supported monophyletic group and eight major clades are proposed here, based on morphological characteristics and phylogenetic inference.

Clade I is characterised by the presence of a viscid pileus, a vivid yellow to greyish-yellow hymenophore that is unchanging when bruised, smooth basidiospores and ixotrichodermium pileipellis. In the present study, this group contains ten species, including the type species A. gentilis and the new species A. sinobadius. This clade is a rather homogeneous group in terms of morphology, which is consistent with the definition of Aureoboletus given by Pouzar (1957). Species in this clade can be separated from each other by pileus colour and the size of basidiospores. In addition, two unsequenced species, A. flavimarginatus and A. flaviporus, should belong to this clade, based on their morphological characteristics (viscid pileus and vivid yellow hymenophore).

Clade II is characterised by the presence of a dry (or slightly sticky when wet) pileus, a vivid yellow to olive yellow hymenophore that is unchanging when bruised, smooth basidiospores and trichodermium pileipellis. This clade includes six species, of which A. velutipes has distinctive morphological characteristics, such as a villous pileus and stipe, pale yellow to olive yellow hymenophore and swollen tips in terminal cells of the stipitipellis.

Clade III is well-characterised by the presence of a viscid pileus with well-developed yellowish to subhyaline veil remnant at the margin, greyish-yellow to olive yellow hymenophore, smooth to longitudinally costate basidiospores and ixotrichodermium pileipellis. Aureoboletus longicollis, originally described from Malaysia, is a well-defined species in this clade and is readily distinguished by its more viscid and larger basidioma, longer stipe and longitudinally costate basidiospores. A Chinese species, A. viscosus, shares similar traits with A. longicollis and the two species cannot be separated from each other in morphology. In this study, we did not have access to specimens of A. longicollis from Malaysia for morphological and phylogenetical study and it is not possible to make a taxonomic decision on whether A. viscosus is the same or a different species to A. longicollis without phylogenetic data. Thus, the name A. longicollis is temporarily used in this study and further studies with more materials are needed. The other species in this clade are characterised by smooth basidiospores and they can be distinguished from each other by their pileus colour and the size of basidiospores.

Clade IV contains the species A. auriflammeus and A. miniatoaurantiacus, which are mainly characterised by their bright orange yellow basidiomata, tomentose pileus surface and ovoid basidiospores. Species in this clade can be easily distinguished from others in this genus.

Clade V is characterised by the presence of a dry or somewhat tacky pileus, greyish-yellow to vivid yellow hymenophore changing to olive yellow when mature and oblong, ovoid to nephroid basidiospores. This clade contains five species, including the two species A. solus and A. raphanaceus described above.

Clade VI is composed of four distinct species, which have all been recently added to Aureoboletus, based on phylogenetic analyses (Halling et al. 2015, Wu et al. 2014, 2016). Aureoboletus projectellus, A. mirabilis and A. russellii were originally described from North America and have a dry or coarsely tomentose pileus, distinct coarse reticulations on the stipe and larger basidiospores (up to 20 μm); however, the basidiospores of A. projectellus and A. mirabilis are smooth, while A. russellii has longitudinally costate basidiospores (Murrill 1938; Singer 1945; Smith and Thiers 1971; Pegler and Young 1981; Bessette et al. 2000). A. shichianus, originally described from southwest China, is a remarkable species in this clade and differs from the others by its small basidiomata, tomentose pileus, radially arranged pores, comparatively long and glabrous stipe and scabrous basidiospores with nodules. Species in this clade are quite diverse, though the coarsely reticulated stipe and ornamented basidiospores are unique in the genus.

Clade VII is currently formed by a single species, A. clavatus. The most striking characteristics are the large basidiomata with slightly viscid pileus, yellowish-white context staining yellowish-olivaceous when exposed, pale yellow to olivaceous-yellow hymenophore, subglobose basidiospores and the pileipellis composed of a turf of clavate hyphae. Besides the slightly viscid pileus, this species shares nearly none of the basic morphological traits of the genus Aureoboletus. However, phylogenetic analyses showed that it belongs to Aureoboletus and formed a separate branch.

Clade VIII is formed by a single species A. griseorufescens. Morphologically, A. griseorufescens is similar to those species in Clade I with a vivid yellow hymenophore and subviscid pileus; however, the most striking characteristic of A. griseorufescens is its white to yellowish-white context changing to greyish-red or greyish-rose when exposed. In the phylogenetic tree, A. griseorufescens formed the basal branch of Aureoboletus with highly-supported values, which showed that it might be an early divergent species from Aureoboletus.

Geographical distribution and species evolution

Aureoboletus is a cosmopolitan genus, but most known species have relatively distinct habitats or regional locations. Currently, most of known Aureoboletus species are distributed in East Asia (mainly in China) and North America and intercontinentally-distributed species are infrequent. Two species A. projectellus and A. mirabilis, originally reported from North America, were examined in several studies and found to have disjunctive distributions in the North Temperate region from North America to Asia (China, Japan) and Europe (Hongo 1973, Chen et al. 1988, Motiejūnaitė et al. 2013, Halling et al. 2015, Wu et al. 2016). In Asia and North America, some morphologically similar and phylogenetically related species also exist. For example, A. auriporus and A. viridiflavus are similar to A. sinobadius and A. formosus and A. auriflammeus is similar to A. miniatoaurantiacus. However, they can be clearly separated from each other by molecular data. In Europe, only A. gentilis was originally described and not found in other continents; this represents a separate geographical region of Aureoboletus.

Phylogenetic analyses based on 144 collections uncovered some useful information regarding the geography of Aureoboletus. Species in Clades III, V and VIII are found in Asia (China-Japan-Malaysia-Vietnam), representing subtropical-tropical Asia distributions. Compared with North America and Europe, China has the greatest number of Aureoboletus species and endemic species, especially in the subtropical-tropical region. Furthermore, many regions in China are under-sampled and more under-described indigenous Aureoboletus species will undoubtedly be discovered in the future. The high diversity of Aureoboletus species in China indicates that the subtropical-tropical region of China (or Asia) is the current species diversity centre of Aureoboletus.

In this study, some evolutionary patterns of morphological characteristics were also discovered. The traits of dry or viscid pileus surface and hymenophore colour appear to be relatively stable evolutionary characteristics and were wellsupported by monophyletic clades on the phylogenetic tree. The shape and surface ornamentation of basidiospores are not reliable characteristics for delimiting Aureoboletus, but are useful for species identification. Basidiospores ornamentation may have evolutionarily originated several times within Aureoboletus history. More morphological and molecular data are needed to understand this trait.

Acknowledgements

The authors are grateful to the editors and anonymous reviewers for their constructive comments and suggestions. Thanks are given to Mr. Hao Huang, Ting Li, Jun-Ping Zou, Zong-Ping Song (Guangdong Institute of Microbiology) and Yu Chen (Guangdong Xiangtoushan National Nature Reserve Administration) for their kind help in the fieldwork; to Dr. Chun-Ying Deng (Guizhou Academy of Sciences) and Dr. Chuan-Hua Li (Institute of Edible Fungi, Shanghai Academy of Agricultural Sciences) for providing collections. This study was supported by the National Natural Science Foundation of China (Nos. 31700021, 31770014, 31670029), the Ministry of Science and Technology of the People’s Republic of China (2013FY111500), the Ministry of Ecology and Environment (2019HB2096001006) and the GDAS’ Special Project of Science and Technology Development (2019GDASYL-0104009).

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