Research Article
Print
Research Article
Phylogenetic affinities of the sequestrate genus Rhodactina (Boletaceae), with a new species, R. rostratispora from Thailand
expand article infoSanthiti Vadthanarat‡, Olivier Raspé§|, Saisamorn Lumyong‡
‡ Chiang Mai University, Chiang Mai, Thailand
§ Botanic Garden Meise, Meise, Belgium
| Fédération Wallonie–Bruxelles, Brussels, Belgium

Corresponding author: Saisamorn Lumyong ( saisamorn.l@cmu.ac.th )

Academic editor: María P. Martín
© 2018 Santhiti Vadthanarat, Olivier Raspé, Saisamorn Lumyong.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Vadthanarat S, Raspé O, Lumyong S (2018) Phylogenetic affinities of the sequestrate genus Rhodactina (Boletaceae), with a new species, R. rostratispora from Thailand. MycoKeys 29: 63-80. https://doi.org/10.3897/mycokeys.29.22572
Open Access

Abstract

Rhodactina is a small sequestrate genus in Boletaceae with two described species, R. himalayensis and R. incarnata. Phylogenetic analyses of a three-gene dataset including atp6, tef1 and rpb2 of Rhodactina species along with selected Boletaceae species showed that all Rhodactina species formed a monophyletic clade, sister to the genera Spongiforma and Borofutus in subfamily Leccinoideae with high support. All of the taxa in the clade have a similar chemical reaction in which basidiospores turn purplish, purplish red to violet or violet grey when in contact with potassium hydroxide. The molecular analyses also showed that all Rhodactina specimens collected from Ubon Ratchathani province, northeastern Thailand, belong to a new species. Morphologically, the new species is different from others by having a markedly prominent hilar appendage and a terminal hilum on its basidiospores. Thus, the new species, Rhodactina rostratispora, is introduced with detailed macroscopic and microscopic descriptions and illustrations.

Keywords

atp6, Boletales , Diversity, Leccinoideae , Phylogeny, Taxonomy

Introduction

The genus Rhodactina Pegler & T.W.K. Young was first described in 1989 with R. himalayensis Pegler & T.W.K. Young, from northwestern India, as the type species. Typical characters of the genus are a whitish to pinkish puffball like basidiomata lacking both stipe and columella, violet brown to purple brown or pale pink to red hymenophore when mature, combined with purplish to purplish red, dextrinoid basidiospores with longitudinal ridges, lack of both clamp connections and cystidia. The genus was originally classified based on morphological characters in the family Gautieriaceae Zeller as the spore ornamentation was originally viewed as similar to the genera Gautieria Vittad and Austrogautieria E.L. Stewart & Trappe (Pegler and Young 1989). In 2006, the second species, R. incarnata Zhu L. Yang, Trappe & Lumyong was described and the known distribution of R. himalayensis was extended to Chiang Mai Province, northern Thailand. Based on the phylogenetic analyses of atp6 sequences, the genus was moved to the family Boletaceae Chevall (Yang et al. 2006). However, the phylogenetic affinities of Rhodactina within the Boletaceae remained unclear because of very limited taxon sampling. So, at present, there are only two described Rhodactina species, R. himalayensis and R. incarnata (http://www.indexfungorum.org/Names/Names.asp), both of which have been reported to occur in northern Thailand (Chandrasrikul et al. 2011).

Boletaceae diversity seems to be high in Thailand (Chandrasrikul et al. 2011), with several new species described in the last five years (Choeyklin et al. 2012, Halling et al. 2014, Neves et al. 2012, Raspé et al. 2016). During this survey of Boletaceae diversity in Thailand, several Rhodactina collections were made and their morphology and phylogenetic relationships were studied. Phylogenetic analyses were based on three genes: atp6, tef1 and rpb2, which have previously been justified as useful for phylogenetic analyses of Boletales (Kretzer and Bruns 1999, Binder and Hibbett 2006, Hosen et al. 2013, Li et al. 2014, Smith et al. 2015, Orihara et al. 2016, Raspé et al. 2016, Wu et al. 2016). Both morphology and phylogenetic analyses confirmed that all newly collected specimens belong to a new species in the genus Rhodactina. Thus, the third species of Rhodactina, found in Thailand, is described and its phylogenetic affinities are presented in this study.

Materials and method

Specimens collecting

The new Rhodactina specimens were collected and photographed from community forests in Trakan Phuet Phon district, Ubon Ratchathani province, northeastern Thailand, in the rainy season during 2015–2017. The specimens were wrapped using aluminium foil or kept in plastic boxes until return to the laboratory and described within 24 h. The specimens were dried in an electric drier at 45–50 °C. The examined specimens are deposited in the herbaria CMUB and BR (both listed in Index Herbariorum; Thiers, continuously updated).

Morphological studies

The macroscopic description was based on detailed field notes and photos of basidiomata. Colour codes followed Kornerup and Wanscher (1978). Macrochemical reactions (colour reactions) of peridium, hymenophore and microscopic structures were determined using 5 % (w/v) aqueous potassium hydroxide, 28–30 % ammonium hydroxide or Melzer’s reagent. Microscopic structures were observed from dried specimens, rehydrated in 5% KOH or 1 % ammoniacal Congo red. For each collection, a minimum of 50 basidiospores and 20 basidia were randomly selected and measured at 1000× with a calibrated ocular micrometer using an Olympus CX31 microscope. Spore dimensions include ornamentation. The notation ‘(n/m/p)’ represents the number of basidiospores n measured from m basidiomata of p collections. Dimensions of microscopic structures are presented in the following format: (a–)b–c–d (–e), in which c represents the average, b the 5th percentile, d the 95th percentile and extreme values a and e are shown in parentheses. Q, the length/width ratio, is presented in the same format. Sections of the peridium surface were made radially and perpendicularly to the surface, halfway between the centre and the side of basidiomata. All microscopic features were drawn free hand using an Olympus Camera Lucida model U−DA fitted to the microscope cited above. For scanning electron microscopy (SEM), small fragments of dried hymenophore were mounted directly on to an SEM stub with double-sided tape. The samples were coated with gold for 60 seconds using SPI-Module Sputter Coater, examined and photographed at 15–20 kV with a FIB Quanta 200 3D scanning electron microscope (Thermo Fisher Scientific, United States).

DNA isolation, PCR amplification and DNA sequencing

Genomic DNA was extracted from fresh tissue preserved in CTAB or about 10–15 mg of dried specimens using a CTAB isolation procedure adapted from Doyle and Doyle (1990). The genes atp6, tef1 and rpb2 were amplified by polymerase chain reaction (PCR) technique. For the amplification of atp6, ATP6-1M40F and ATP6-2Mprimers were used (Raspé et al. 2016), with the following PCR programme: 2 min at 95 °C; 5 cycles of 45 s at 95 °C, 60 s at 42 °C, 30 s at 72 °C; 35 cycles of 20 s at 95 °C, 30 s at 55 °C, 30 s+1 s/cycle at 72 °C; 3 min at 72 °C. The primers EF1-983F and EF1-2218R (Rehner and Buckley 2005) were used to amplify tef1 and bRPB2-6F and bRPB2-7.1R primers (Matheny 2005) were used to amplify rpb2. PCR products were purified by adding 1 U of Exonuclease I and 0.5 U FastAP Alkaline Phosphatase (Thermo Scientific, St. Leon-Rot, Germany) and incubated at 37 °C for 1 h, followed by inactivation at 80 °C for 15 min. Sequencing was performed by Macrogen Inc. (Korea and The Netherlands) with PCR primers, except for atp6, for which universal primers M13F-pUC(-40) and M13F(-20) were used; for tef1, additional sequencing was performed with the two internal primers, EF1-1577F and EF1-1567R (Rehner and Buckley 2005).

Alignment and phylogeny inference

The sequences were assembled in GENEIOUS Pro v. 6.0.6 (Biomatters) and introns were removed prior to alignment based on the amino acid sequence of previously published sequences. All sequences, including sequences from GenBank, were aligned using MAFFT (Katoh and Standley 2013) on the server accessed at http://mafft.cbrc.jp/alignment/server/. Maximum Likelihood (ML) phylogenetic tree inference was performed using RAxML (Stamatakis 2006) on the CIPRES web server (RAxML-HPC2 on XSEDE; Miller et al. 2009). The phylogenetic tree was inferred by a single analysis with three partitions (one for each gene), using the GTRCAT model with 25 categories and three Chalciporus species were used as an outgroup. Statistical support of nodes was obtained with 1,000 bootstrap replicates.

Results

DNA analyses

A total of 127 new sequences were generated and deposited in GenBank (Table 1). The alignment contained 157 taxa spread over the entire family Boletaceae and was 2429 characters long (TreeBase number 21933). The authors could not obtain tef1 and rpb2 sequences from R. incarnata (CMU25116) nor rpb2 sequence from R. himalayensis (CMU25117). The specimens were in relatively poor condition and genomic DNA was highly degraded. The 3-gene phylogram indicated that all selected collections of the new taxon R. rostratispora formed a monophyletic group with high bootstrap support sister to R. incarnata within the Rhodactina clade (Figure 1). The Rhodactina clade was sister to a clade composed of the genera Spongiforma Desjardin, Manfr. Binder, Roekring & Flegel and Borofutus Hosen & Zhu L. Yang, within the subfamily Leccinoideae G. Wu & Zhu L. Yang clade. Interestingly, the genera Rhodactina, Spongiforma and Borofutus formed a clade with 100% bootstrap support.

Table 1.
Download as
CSV
XLSX

List of collections used for DNA analyses, with origin, GenBank accession numbers and reference(s).

Species Voucher Origin atp6 tef1 rpb2 References
Afroboletus costatisporus ADK4644 Togo KT823958 KT824024 KT823991 Raspé et al. 2016
Aureoboletus catenarius HKAS54467 China – KT990711 KT990349 Wu et al. 2016
Aureoboletus duplicatoporus HKAS50498 China – KF112230 KF112754 Wu et al. 2014
Aureoboletus gentilis ADK4865 Belgium KT823961 KT824027 KT823994 Raspé et al. 2016
Aureoboletus moravicus VDKO1120 Belgium MG212528 MG212573 MG212615 This study
Aureoboletus nephrosporus HKAS67931 China – KT990720 KT990357 Wu et al. 2016
Aureoboletus projectellus AFTOL 713 U.S.A. DQ534604* AY879116 AY787218 Binder and Hibbett 2006*; Binder et al. unpubl.
Aureoboletus thibetanus HKAS76655 China – KF112236 KF112752 Wu et al. 2014
Aureoboletus tomentosus HKAS80485 China – KT990715 KT990353 Wu et al. 2016
Aureoboletus viscosus HKAS53398 China – KF112238 KF112755 Wu et al. 2014
Aureoboletus zangii HKAS74766 China – KT990726 KT990363 Wu et al. 2016
Austroboletus cf. dictyotus OR045 Thailand KT823966 KT824032 KT823999 Raspé et al. 2016
Austroboletus olivaceoglutinosus HKAS57756 China – KF112212 KF112764 Wu et al. 2014
Austroboletus sp. HKAS59624 China – KF112217 KF112765 Wu et al. 2014
Baorangia pseudocalopus HKAS63607 China – KF112167 KF112677 Wu et al. 2014
Baorangia pseudocalopus HKAS75739 China – KJ184570 KM605179 Wu et al. 2015
Boletellus aff. emodensis OR061 Thailand KT823970 KT824036 KT824003 Raspé et al. 2016
Boletellus sp. HKAS58713 China – KF112307 KF112759 Wu et al. 2014
Boletellus sp. HKAS59536 China – KF112306 KF112758 Wu et al. 2014
Boletellus sp. OR0621 Thailand MG212529 MG212574 MG212616 This study
Boletus aereus VDKO1055 Belgium MG212530 MG212575 MG212617 This study
Boletus albobrunnescens OR131 Thailand KT823973 KT824039 KT824006 Raspé et al. 2016
Boletus botryoides HKAS53403 China – KT990738 KT990375 Wu et al. 2016
Boletus edulis VDKO0869 Belgium MG212531 MG212576 MG212618 This study
Boletus s.s. sp. OR0446 China MG212532 MG212577 MG212619 This study
Boletus erythropus VDKO0690 Belgium KT823982 KT824048 KT824015 Raspé et al. 2016
Borofutus dhakanus HKAS73789 Bangladesh – JQ928576 JQ928597 Hosen et al. 2013
Borofutus dhakanus HKAS73785 Bangladesh – JQ928577 JQ928596 Hosen et al. 2013
Borofutus dhakanus OR345 Thailand MG212533 MG212578 MG212620 This study
Borofutus dhakanus OR352 Thailand MG212534 MG212579 MG212621 This study
Borofutus dhakanus SV210 Thailand MG212535 MG212580 MG212622 This study
Borofutus dhakanus SV245 Thailand MG212536 MG212581 MG212623 This study
Butyriboletus appendiculatus VDKO0193b Belgium MG212537 MG212582 MG212624 This study
Butyriboletus pseudoregius VDKO0925 Belgium MG212538 MG212583 MG212625 This study
Butyriboletus pseudospeciosus HKAS63513 China – KT990743 KT990380 Wu et al. 2016
Butyriboletus roseoflavus HKAS54099 China – KF739779 KF739703 Wu et al. 2014
Butyriboletus subsplendidus HKAS50444 China – KT990742 KT990379 Wu et al. 2016
Butyroboletus cf. roseoflavus OR230 China KT823974 KT824040 KT824007 Raspé et al. 2016
Caloboletus calopus ADK4087 Belgium MG212539 KJ184566 KP055030 This study; Zhao et al. 2014a; Zhao et al. 2014b
Caloboletus radicans VDKO1187 Belgium MG212540 MG212584 MG212626 This study
Caloboletus yunnanensis HKAS69214 China – KJ184568 KT990396 Zhao et al. 2014a; Wu et al. 2016
Chalciporus aff. piperatus OR586 Thailand KT823976 KT824042 KT824009 Raspé et al. 2016
Chalciporus africanus JD517 Cameroon KT823963 KT824029 KT823996 Raspé et al. 2016
Chalciporus rubinus AF2835 Belgium KT823962 KT824028 KT823995 Raspé et al. 2016
Chiua virens OR0266 China MG212541 MG212585 MG212627 This study
Chiua viridula HKAS74928 China – KF112273 KF112794 Wu et al. 2014
Crocinoboletus cf. laetissimus OR576 Thailand KT823975 KT824041 KT824008 Raspé et al. 2016
Cyanoboletus brunneoruber OR0233 China MG212542 MG212586 MG212628 This study
Cyanoboletus pulverulentus RW109 Belgium KT823980 KT824046 KT824013 Raspé et al. 2016
Cyanoboletus sp. OR0257 China MG212543 MG212587 MG212629 This study
Fistulinella prunicolor REH9502 Australia MG212544 MG212588 MG212630 This study
Harrya chromapes KPM NC17835 Japan KC552173 JN378457 – Orihara et al. 2016; Orihara et al. 2012
Harrya moniliformis HKAS49627 China – KT990881 KT990500 Wu et al. 2016
Heimioporus cf. mandarinus OR0661 Thailand MG212545 MG212589 MG212631 This study
Heimioporus japonicus OR114 Thailand KT823971 KT824037 KT824004 Raspé et al. 2016
Heimioporus retisporus HKAS52237 China – KF112228 KF112806 This study
Heimioporus sp. OR0218 Thailand MG212546 MG212590 MG212632 This study
Hemileccinum depilatum AF2845 Belgium MG212547 MG212591 MG212633 This study
Hemileccinum impolitum ADK4078 Belgium MG212548 MG212592 MG212634 This study
Hemileccinum rugosum HKAS84970 China – KT990773 KT990412 Wu et al. 2016
Hourangia cheoi HKAS74744 China – KF112285 KF112772 Wu et al. 2014
Hourangia nigropunctata HKAS 57427 China – KP136927 KP136978 Zhu et al. 2015
Hymenoboletus luteopurpureus HKAS46334 China – KF112271 KF112795 Wu et al. 2014
Imleria badia VDKO0709 Belgium KT823983 KT824049 KT824016 Raspé et al. 2016
Lanmaoa angustispora HKAS74752 China – KM605154 KM605177 Wu et al. 2015
Lanmaoa asiatica HKAS63603 China – KM605153 KM605176 Wu et al. 2015
Leccinellum crocipodium VDKO1006 Belgium KT823988 KT824054 KT824021 Raspé et al. 2016
Leccinellum sp. KPM-NC-0018041 Japan KC552165 KC552094 – Orihara et al. 2016
Leccinum scabrum VDKO0938 Belgium MG212549 MG212593 MG212635 This study
Leccinum scabrum RW105a Belgium KT823979 KT824045 KT824012 Raspé et al. 2016
Leccinum scabrum KPM-NC-0017840 Scotland KC552170 JN378455 – Orihara et al. 2016; Orihara et al. 2012
Leccinum schistophilum VDKO1128 Belgium KT823989 KT824055 KT824022 Raspé et al. 2016
Leccinum variicolor VDKO0844 Belgium MG212550 MG212594 MG212636 This study
Leccinum versipelle KPM-NC-0017833 Scotland KC552172 JN378454 – Orihara et al. 2016; Orihara et al. 2012
Leccinum vulpinum KPM-NC-0017834 Scotland KC552171 JN378456 – Orihara et al. 2016; Orihara et al. 2012
Mucilopilus castaneiceps HKAS75045 China – KF112211 KF112735 Wu et al. 2014
Neoboletus brunneissimus HKAS50538 China – KM605150 KM605173 Wu et al. 2015
Neoboletus brunneissimus OR0249 China MG212551 MG212595 MG212637 This study
Neoboletus junquilleus AF2922 France MG212552 MG212596 MG212638 This study
Neoboletus magnificus HKAS54096 China – KF112149 KF112654 Wu et al. 2014
Neoboletus venenatus HKAS63535 China – KT990807 KT990448 Wu et al. 2016
Octaviania asahimontana KPM-NC17824 Japan KC552154 JN378430 – Orihara et al. 2016; Orihara et al. 2012
Octaviania asterosperma AQUI3899 Italy KC552159 KC552093 – Orihara et al. 2016
Octaviania celatifilia KPM-NC17776 Japan KC552147 JN378416 – Orihara et al. 2016; Orihara et al. 2012
Octaviania decimae KPM-NC17763 Japan KC552145 JN378409 – Orihara et al. 2016; Orihara et al. 2012
Octaviania tasmanica MEL2341996 Australia KC552156 JN378436 – Orihara et al. 2016; Orihara et al. 2012
Octaviania zelleri MES270 U.S.A. KC552161 JN378440 – Orihara et al. 2016; Orihara et al. 2012
Phylloporus brunneiceps OR050 Thailand KT823968 KT824034 KT824001 Raspé et al. 2016
Phylloporus castanopsidis OR052 Thailand KT823969 KT824035 KT824002 Raspé et al. 2016
Phylloporus imbricatus HKAS68642 China – KF112299 KF112786 Wu et al. 2014
Phylloporus luxiensis HKAS75077 China – KF112298 KF112785 Wu et al. 2014
Phylloporus yunnanensis OR0448 China MG212554 MG212598 MG212640 This study
Porphyrellus castaneus OR0241 China MG212555 MG212599 MG212641 This study
Porphyrellus porphyrosporus MB97-023 Germany DQ534609 GU187734 GU187800 Binder and Hibbett 2006; Binder et al. 2010
Pulveroboletus aff. ravenelii ADK4360 Togo KT823957 KT824023 KT823990 Raspé et al. 2016
Pulveroboletus aff. ravenelii ADK4650 Togo KT823959 KT824025 KT823992 Raspé et al. 2016
Pulveroboletus aff. ravenelii HKAS53351 China – KF112261 KF112712 Wu et al. 2014
Pulveroboletus fragrans OR673 Thailand KT823977 KT824043 KT824010 Raspé et al. 2016
Pulveroboletus ravenelii REH2565 U.S.A. KU665635 KU665636 KU665637 Raspé et al. 2016
Pulveroboletus sp. HKAS74933 China – KF112262 KF112713 Wu et al. 2014
Retiboletus aff. nigerrimus OR049 Thailand KT823967 KT824033 KT824000 Raspé et al. 2016
Retiboletus fuscus OR0231 China MG212556 MG212600 MG212642 This study
Retiboletus griseus MB03-079 U.S.A. KT823964 KT824030 KT823997 Raspé et al. 2016
Retiboletus kauffmanii OR0278 China MG212557 MG212601 MG212643 This study
Retiboletus nigerrimus HKAS53418 China – KT990824 KT990462 Wu et al. 2016
Retiboletus sinensis HKAS59832 China – KT990827 KT990464 Wu et al. 2016
Rhodactina himalayensis CMU25117 Thailand MG212558 MG212602, MG212603 – This study
Rhodactina incarnata CMU25116 Thailand DQ328982 – – Yang et al. 2006
Rhodactina rostratispora OR1055 Thailand MG212559 MG212604 MG212644 This study
Rhodactina rostratispora SV170 Thailand MG212560 MG212605 MG212645 This study
Rhodactina rostratispora SV208 Thailand MG212561 MG212606 MG212646 This study
Rossbeevera cryptocyanea KPM-NC17843 Japan KT581441 KC552072 – Orihara et al. 2016
Rossbeevera eucyanea TNS-F-36986 Japan KC552115 KC552068 – Orihara et al. 2016
Rossbeevera griseovelutina TNS-F-36989 Japan KC552124 KC552076 – Orihara et al. 2016
Rossbeevera pachydermis KPM-NC23336 New Zealand KJ001064 KP222912 – Orihara et al. 2016
Rossbeevera vittatispora TO-AUS-72 Australia KC552108 KC552065 – Orihara et al. 2016
Royoungia reticulata HKAS52253 China – KT990786 KT990427 Wu et al. 2016
Royoungia rubina HKAS53379 China – KF112274 KF112796 Wu et al. 2014
Rubroboletus legaliae VDKO0936 Belgium KT823985 KT824051 KT824018 Raspé et al. 2016
Rubroboletus satanas VDKO0968 Belgium KT823986 KT824052 KT824019 Raspé et al. 2016
Rubroboletus sinicus HKAS56304 China – KJ619483 KP055031 Zhao et al. 2014a; Zhao et al. 2014b
Rugiboletus brunneiporus HKAS83209 China – KM605144 KM605168 Wu et al. 2015
Rugiboletus extremiorientalis HKAS76663 China – KM605147 KM605170 Wu et al. 2015
Rugiboletus extremiorientalis OR0406 Thailand MG212562 MG212607 MG212647 This study
Spongiforma thailandica DED7873 Thailand MG212563 KF030436* MG212648 Nuhn et al. 2013*; This study
Strobilomyces atrosquamosus HKAS55368 China – KT990839 KT990476 Wu et al. 2016
Strobilomyces echinocephalus OR0243 China MG212564 MG212608 MG212649 This study
Strobilomyces floccopus RW103 Belgium KT823978 KT824044 KT824011 Raspé et al. 2016
Strobilomyces mirandus OR115 Thailand KT823972 KT824038 KT824005 Raspé et al. 2016
Strobilomyces sp. OR0259 China MG212565 MG212609 MG212650 This study
Strobilomyces sp. OR0778 Thailand MG212566 MG212610 MG212651 This study
Strobilomyces verruculosus HKAS55389 China – KF112259 KF112813 Wu et al. 2014
Suillellus luridus VDKO0241b Belgium KT823981 KT824047 KT824014 Raspé et al. 2016
Suillellus subamygdalinus HKAS53641 China – KT990841 KT990478 Wu et al. 2016
Sutorius australiensis REH9441 Australia MG212567 JQ327032* MG212652 Halling et al. 2012*; This study
Sutorius eximius REH9400 U.S.A. MG212568 JQ327029* MG212653 Halling et al. 2012*; This study
Turmalinea persicina KPM-NC18001 Japan KC552130 KC552082 – Orihara et al. 2016
Turmalinea yuwanensis KPM-NC18011 Japan KC552138 KC552089 – Orihara et al. 2016
Tylocinum griseolum HKAS50281 China – KF112284 KF112730 Wu et al. 2014
Tylopilus atripurpureus HKAS50208 China – KF112283 KF112799 Wu et al. 2014
Tylopilus balloui s.l. OR039 Thailand KT823965 KT824031 KT823998 Raspé et al. 2016
Tylopilus felleus VDKO0992 Belgium KT823987 KT824053 KT824020 Raspé et al. 2016
Tylopilus sp. OR0252 China MG212569 MG212611 MG212654 This study
Tylopilus sp. OR0542 Thailand MG212570 MG212612 MG212655 This study
Tylopilus vinaceipallidus OR0137 China MG212571 MG212613 MG212656 This study
Veloporphyrellus alpinus HKAS57490 China JX984514 JX984549 – Li et al. 2014
Veloporphyrellus conicus CFMR BZ1670 Belize JX984520 JX984555 – Li et al. 2014
Veloporphyrellus pseudovelatus HKAS52258 China JX984517 JX984551 – Li et al. 2014
Veloporphyrellus velatus HKAS63668 China JX984523 JX984554 – Li et al. 2014
Xerocomellus chrysenteron VDKO0821 Belgium KT823984 KT824050 KT824017 Raspé et al. 2016
Xerocomellus cisalpinus ADK4864 Belgium KT823960 KT824026 KT823993 Raspé et al. 2016
Xerocomus fulvipes HKAS76666 China – KF112292 KF112789 Wu et al. 2014
Xerocomus subtomentosus VDKO0987 Belgium MG212572 MG212614 MG212657 This study
Zangia citrina HKAS52684 China HQ326850 HQ326872 – Li et al. 2011
Zangia olivacea HKAS55830 China HQ326855 HQ326874 – Li et al. 2011
Zangia olivaceobrunnea HKAS52275 China HQ326856 HQ326875 – Li et al. 2011
Zangia roseola HKAS51137 China HQ326858 HQ326877 – Li et al. 2011
Figure 1. 

Maximum likelihood phylogenetic tree inferred from the three-gene dataset (atp6, rpb2, tef1), including Rhodactina rostratispora and selected Boletaceae. The three Chalciporus species were used as outgroup taxa. Most of the taxa not belonging to the subfamily Leccinoideae were collapsed into subfamilies or similar level clade (i.e. Pulveroboletus group). Bootstrap support values > 70% are shown above branches.

Taxonomy

Key to the species of Rhodactina

1 Basidiospores with a markedly prominent hilar appendage 2.5–5 µm long and 3.5–5 µm wide with a terminal hilum, spore size 12–16 × 10–14 µm R. rostratispora sp. nov.
– Basidiospores without markedly prominent hilar appendage or with short to nearly truncate hilar appendage up to 1.5 µm long and 1.5 µm wide 2
2 Basidiospores bearing large (5)6–7(8) longitudinal ridges, 3–4 µm wide, up to 5 µm tall, dark violet in 5 % KOH, spore size 15–20 × 12.5–18 µm R. himalayensis
– Basidiospores bearing (7)8–9(10) longitudinal ridges, 2–3 µm wide, up to 3 µm tall, slightly reddish to purplish yellow in 5 % KOH, spore size 10–13 × 10–12 µm R. incarnata

Rhodactina rostratispora Vadthanarat, Raspé & Lumyong, sp. nov.

MycoBank No: 822126
Figs 2, 3, 4

Type

THAILAND, Ubon Ratchathani Province, Trakan Phuet Phon District, Don Khok Tam Lae community forest, 15°35'46"N, 105°06'38"E, elev. 150 m., 28 July 2015, S. Vadthanarat 170, (holotype: CMUB!; isotype: BR!).

Etymology

From Latin “rostrati–” meaning having beaked prow or a solid projection and “spora” meaning spores, referring to the basidiospores having a markedly prominent and large hilar appendage.

Description

Basidiomata small to medium-sized 0.8–2.5(4.5) cm diam., subglobose to ovoid with a rudimentary elongated basal attachment, with greyish white to pale brown rhizoids at the base and going up along the surface of basidiomata to about half of the height. Peridium surface (outer peridium) fibrillose to arachnoid, off-white to pinkish white (7A2–3 to 9A2), dull, moist, cracked in places. Peridium very thin, 0.1–0.2(0.4) mm thick. Hymenophore cartilaginous, completely enclosed, whitish orange to reddish orange (7A3–4 to 8A5–6) at first becoming orangey red to red (9D–E8 to 10D–E8) with age, then dark red when very old, irregular; Stipe-columella absent. Taste fungoid. Odour absent when young, very strongly fruity alcoholic when old.

Macrochemical reactions: hymenophore turned dark purplish (15F8) to greyish violet (19D3) with 5% KOH, slightly greyish violet (19D3) with NH4OH.

Basidiospores [404/8/8] (11.5–)12–13.6–15(–16) × (10–)10.5–11.7–13(–14), Q = (1–)1.04–1.16–1.3(–1.4), from the holotype, (12–)12–13.5–15.2(–16) × (10–)10–11.6–13.2(–14) µm, Q = (1–)1–1.02–1.33(–1.4), N = 50, ellipsoid to broadly ellipsoid with longitudinal ridges, stellate in polar-view, thick-walled (1–1.5 µm thick), yellowish to orangey hyaline to reddish yellow at first, reddish to brownish yellow with age in water, slightly purplish and slightly more reddish to brownish in 5% KOH, slightly purplish hyaline in NH4OH, slightly dextrinoid to dextrinoid in Melzer’s reagent; ornamentation (7)8–9 solid ridges regularly and longitudinally arranged under light microscope, sometimes anastomosing under SEM, 2–3 µm tall and 2–2.5 µm wide at the base; hilar appendage prominent, 2.5–5 µm long with a terminal hilum. Basidia 4–spored, (26–)26.1–32.3–36(–36) × (8–)8–9.5–11(–11) µm (n = 20; from holotype only), clavate to cylindrical, hyaline in water, 5% KOH and NH4OH, yellowish hyaline in Melzer’s reagent; sterigmata broken by spore release, stout, 3–4 µm long. Cystidia none observed. Hymenophoral trama 60–130 µm thick, irregular, with a narrow, central layer of subparallel to loosely interwoven, 3–7(8) µm wide, thin-walled hyphae, slightly gelatinised, hyaline in water, 5% KOH and NH4OH. Peridiopellis a tomentum 45–120 µm thick, poorly differentiated, composed of thin-walled, 3–10 µm wide hyphae, anastomosing at places and covered with yellowish brown incrustations on the surface at places, otherwise hyaline in water, 5% KOH and NH4OH, inamyloid. Clamp connections not seen in any of the tissues.

Figure 2. 

Basidiomata of Rhodactina rostratispora A S. Vadthanarat 170 (holotype) B S. Vadthanarat 206 C S. Vadthanarat 208 D O. Raspé 1055 E S. Vadthanarat 406, showing one basidioma (white arrow) that had a strong fruity alcoholic smell F Hymenophore turned dark purple to greyish violet with 5% KOH (white arrow). Scale bars: A–E = 1 cm; F =0.5 cm.

Figure 3. 

Microscopic features of Rhodactina rostratispora A Basidiospores in side view, polar view and optical section B Basidia C Hymenium showing basidia and basidioles D Peridiopellis covered with some encrustations. All drawings were made from the type. Scale bars: A = 10 µm; B–C = 20 µm; D = 50 µm.

Figure 4. 

Scanning electron micrographs of basidiospores A–B Rhodactina himalayensis (CMU25117) showing the basidiospores with 6–7 longitudinal ridges C–D Rhodactina incarnata (CMU25116, holotype) showing the basidiospores with 8–9 longitudinal ridges E–F Rhodactina rostratispora (O. Raspé 1055) showing the basidiospores with 8–9 longitudinal ridges, the wide and prominent hilar appendage (ha), a terminal hilum (th) and anastomosing ridges in some spores (as).

Habit and habitat

Subepigeal, solitary to gregarious (4–7 basidiomata), or fasciculate by 2–5 basidiomata, on sandy soil in dipterocarp forest dominated by Dipterocarpus tuberculatus, D. intricatus, D. obtusifolius, Shorea obtusa, S. siamensis and Eucalyptus sp.

Known distribution

Currently found only from Ubon Ratchathani province, northeastern Thailand.

Additional specimens examined

Rhodactina rostratispora.—THAILAND, Ubon Ratchathani Province, Trakan Phuet Phon District, Don Khok Tam Lae community forest, 15°35'40.2"N–105°06'37.8"E, elev. 150 m., 28 July 2015, S. Vadthanarat 169, (CMUB, BR); ibid. 15°35'41.5"N–105°06'35.4"E, elev. 150 m., 28 July 2015, O. Raspé 1055, (CMUB, BR); ibid. 15°35'48.3"N –105°06'35.9"E, elev. 150 m., 6 August 2015, S. Vadthanarat 206, (CMUB, BR); ibid. 15°35'52.4"N–105°06'41.2"E, elev. 150 m., 6 August 2015, S. Vadthanarat 208, (CMUB, BR); ibid. 15°35'56.1"N–105°06'38.9"E, elev. 150 m., 6 August 2015, S. Vadthanarat 212, (CMUB, BR); ibid. 15°36'2.6"N–105°06'36.7"E, elev. 150 m., 14 May 2017, S. Vadthanarat 376, (CMUB, BR); Ban Huay Fai community forest, 15°32'42.7"N–105°10'16.3"E, elev. 160 m., 15 July 2017, S. Vadthanarat 406, (CMUB, BR).

R. himalayensis. – THAILAND, Chiang Mai Province, Doi Suthep-Pui National Park, forest behind Channel 9 TV station, 4 August 2000, Saisamorn Lumyong, Pipob Lumyong, Rarunee Sanmee and B. Dell 2254 (CMU25117).

R. incarnata. – THAILAND, Chiang Mai Province, Sanpatong District, Mae Wang, Conservation forest, Sanpatong-Ban Guard Rd., 24 July 2002, Saisamorn Lumyong, Pipob Lumyong, Rarunee Sanmee and Zhu L. Yang 45209 (CMU25116; holotype).

Remarks

Rhodactina rostratispora is characterised by its basidiospores having a markedly prominent hilar appendage (2.5–5 µm long, 3.5–5 µm wide), with a terminal hilum; ornamentation consisting of (7)8–9 longitudinal ridges, and (11.5–)12–13.6–15(–16) × (10–)10.5–11.7–13(–14) µm. R. himalayensis has larger basidiospores (15–20 × 12.5–18 µm) without prominent hilar appendage, with fewer [(5)6–7(8)], broader ridges, while R. incarnata has a similar spore size (10–13 × 10–12 µm) and the same number of spore ridges [(7)8–9(10)] as the new species, but it does not have the prominent hilar appendage.

In one R. rostratispora specimen (S. Vadthanarat 208), abnormal spores were observed. Those spores were elongated, 21–24 × 4–8 µm, thick-walled, narrowly fusiform to bacilliform, with or without longitudinal ridges, more or less constricted in the middle. They were usually found attached to apparently normal basidia with four sterigmata.

Discussion

Morphologically, the new species R. rostratispora is characterised by its ridged basidiospores having a markedly prominent hilar appendage with a terminal hilum, which is not found in other Rhodactina species (Pegler and Young 1989, Yang et al. 2006). However, ridged basidiospores having a prominent hilar appendage are found in some other sequestrate Boletaceae in the genus Turmalinea Orihara & N. Maek and Rossbeevera, including T. persicina Orihara, T. chrysocarpa Orihara & Z.W. Ge, T. mesomorpha Orihara, Ro. paracyanea Orihara and Ro. cryptocyanea Orihara. The basidiospores of those species have a long pointed hilar appendage 4.5–6 µm (Orihara et al. 2016) but are not as wide as in R. rostratispora (2.5–5 µm long, 3.5–5 µm wide) and also their hilar appendage lacks a terminal hilum. Macroscopically, those species differ from R. rostratispora in that both Rossbeevera and Turmalinea have basidiomata often turning blue to greenish blue when bruised, which has never been reported in any Rhodactina species (Pegler and Young 1989, Yang et al. 2006). Moreover, the colour of mature hymenophore of Turmalinea and Rossbeevera species are dark brown or blackish brown (Lebel et al. 2012, Orihara et al. 2016) not red or dark red like in Rhodactina.

The phylogenetic analyses also support the placement of the new taxon in the genus Rhodactina, with R. incarnata being the closest species. The phylogenetic tree also showed that Rhodactina is sister to a clade composed of Spongiforma and Borofutus within the subfamily Leccinoideae, with 100% bootstrap support. According to Wu et al. (2016), there are 10 genera in the sub-family Leccinoideae including Borofutus, Chamonixia Rolland, Leccinum Gray, Leccinellum Bresinsky & Manfr. Binder, Octaviania Vittad, Pseudoaustroboletus Y.C. Li & Zhu L. Yang, Retiboletus Manfr. Binder & Bresinsky, Rossbeevera T. Lebel & Orihara & N. Maek, Spongiforma and Tylocinum Yan C. Li & Zhu L. Yang. The phylogenetic analyses infer that Rhodactina is the eleventh genus in the subfamily.

In the examination of R. rostratispora, it was found that the hymenophore turned dark purplish to greyish violet with 5% KOH. Interestingly, all of the genera in subfamily Leccinoideae that turn purple to violet with aqueous KOH solution, namely Rhodactina, Borofutus and Spongiforma, are grouped in one clade with 100% bootstrap support. All of the species in the clade share the characteristic of the basidiospores turning more or less purplish, purplish red to violet grey in aqueous KOH solution (Desjardin et al. 2009, Hosen et al. 2013). Spongiforma squarepantsii Desjardin, Peay & T.D. Bruns, which was described from Malaysia, was not included in these analyses, but the original description of this species also mentioned that its basidiospores turn pale lilac grey in 3% KOH (Desjardin et al. 2011). A chemical reaction with KOH was observed not only with basidiospores, but also on the hymenophore (Desjardin et al. 2009). The reaction to 5% KOH has been observed on fresh basidiomata of Borofutus dhakanus Hosen & Zhu L. Yang which is an epigeous species and the only currently known species of this genus. The colour reaction of pileus and pileus context, which turned pinkish blue to purplish blue, was different from that of the stipe and stipe context, which turned yellowish green to olive green. This variation in colour of the reaction to 5% KOH was not mentioned in the original description of the species (Hosen et al. 2013). Therefore, this chemical character is very useful for the identification of boletes belonging to this group. Other taxa that have been reported to show similar colour reactions to KOH and would, therefore, belong to this group, include Austroboletus longipes (Massee) Wolfe, Austroboletus malaccensis (Pat. & C.F. Baker) Wolfe and Austroboletus tristis (Pat. & C.F. Baker) Wolfe (Corner 1972, Horak 2011).

Some basidiomata of R. rostratispora were old when collected, with dark red hymenophore and had a very strong fruity, alcoholic odour. The odour seems to be present in old basidiomata only (S. Vadthanarat 212 and one basidiomata of S. Vadthanarat 406). One possible explanation to the alcoholic smell is that sterigmata are broken from spore release and any remaining cytoplasm in the basidia could leak into the cavities of the hymenophore and be fermented. Fermentation by yeasts might be possible due to the cracking of the peridium, allowing contact of the hymenophore cavities with ambient air. As mammals and marsupials are known to be the main spore dispersal vectors of truffle-like fungi (e.g. Lamont et al. 1985, Cázares and Trappe 1994, Vernes and Dunn 2009), the strong alcoholic smell could facilitate detection and entice consumption of the basidiomata by mammals and thus help spore dispersal.

The three Rhodactina species were found only in dipterocarp forest between 100 to 600 m above sea level in India, northern and northeastern Thailand (Pegler and Young 1989, Yang et al. 2006). They presumably form ectomycorrhizal associations with trees of the genera Dipterocarpus and Shorea (Dipterocarpaceae). However, in the forest where the new species was found, some scattered Eucalyptus trees were also observed. As Eucalyptus species have been reported to be ectomycorrhizal trees (e.g. Giachini et al. 2000, Ducousso et al. 2012, Garrett Kluthe et al. 2016), the Eucalyptus trees found in the forest could also possibly be host of R. rostratispora. However, Eucalyptus is not indigenous to Thailand; several species have been planted since the early 1900s (Luangviriyasaeng 2003). As Rhodactina species seem to be indigenous to Thailand and Eucalyptus not, they are less likely to be ectomycorrhizal partners. Further study is needed, however, to confirm the range of ectomycorrhizal host tree species of R. rostratispora. Borofutus and Spongiforma, the most closely related genera of Rhodactina, are also ectomycorrhizal associates with trees in Dipterocarpaceae. The only known Borofutus species, B. dhakanus is ectomycorrhizal with Shorea robusta (Hosen et al. 2013). As for Spongiforma species, S. thailandica was reported as associated with Dipterocarpus sp. and Shorea sp. in primary forest while S. squarepantsii was reported as associated with unidentified dipterocarp trees (Desjardin et al. 2009, Desjardin et al. 2011).

Acknowledgments

Financial support from the Graduate School, Chiang Mai University, is appreciated. The work was partly supported by a TRF Research Team Association Grant (RTA 5880006) to SL and OR and by the Higher Education Research Promotion and the Thai Centre of Excellence on Biodiversity (BDC-PG2-159013) and Center of Excellence in Bioresources for Agriculture, Industry and Medicine, Faculty of Science, Chiang Mai University. OR is grateful to the Fonds National de la Recherche Scientifique (Belgium) for travel grants. The authors are grateful to Dennis Desjardin and Roy Halling for the loan of specimens. The comments of Roy Halling and Roy Watling helped improving the article and are gratefully acknowledged.

References

  • Binder M, Larsson KH, Matheny Hibbett DS (2010) Amylocorticiales ord. nov. and Jaapiales ord. nov.: early diverging clades of Agaricomycetidae dominated by corticioid forms. Mycologia 102: 865–880. https://doi.org/10.3852/09-288
  • Cázares E, Trappe JM (1994) Spore dispersal of ectomycorrhizal fungi on a glacier forefront by mammal mycophagy. Mycologia 86: 507–510. https://doi.org/10.2307/3760743
  • Chandrasrikul A, Suwanarit P, Sangwanit U, Lumyong S, Payapanon A, Sanoamuang N, Pukahuta C, Petcharat V, Sardsud U, Duengkae K, Klinhom U, Thongkantha S, Thongklam S (2011) Checklist of Mushrooms (Basidiomycetes) in Thailand. Office of Natural Resources and Environmental Policy and Planning, Bangkok, Thailand, 1–448.
  • Corner EJH (1972) Boletus in Malaysia. Gov. Printer, Singapore, 1–263.
  • Desjardin DE, Binder M, Roekring S, Flegel T (2009) Spongiforma, a new genus of gasteroid boletes from Thailand. Fungal Diversity 37: 1–8.
  • Desjardin DE, Peay KG, Bruns TD (2011) Spongiforma squarepantsii, a new species of gasteroid bolete from Borneo. Mycologia 103(5): 1119–1123. https://doi.org/10.3852/10-433
  • Doyle JJ, Doyle JL (1990) Isolation of plant DNA from fresh tissue. Focus 12: 13–15.
  • Ducousso M, Duponnois R, Thoen D, Prin Y (2012) Diversity of ectomycorrhizal fungi associated with Eucalyptus in Africa and Madagascar. International Journal of Forestry Research 2012: 1–10. https://doi.org/10.1155/2012/450715
  • Garrett Kluthe B, Ben Hassine Ben Ali M, Nelsen DJ, Stephenson SL (2016) A preliminary study of the ectomycorrhizal fungi associated with introduced Eucalyptus in Kenya. Mycosphere 7(1): 81–86.
  • Giachini AJ, Oliveira VL, Castellano MA, Trappe JM (2000) Ectomycorrhizal fungi in Eucalyptus and Pinus plantations in Southern Brazil. Mycologia 92(6): 1166–1177. https://doi.org/10.2307/3761484
  • Halling RE, Desjardin DE, Fechner N, Arora D, Soytong K, Dentinger BTM (2014) New porcini (Boletus sect. Boletus) from Australia and Thailand. Mycologia 106: 830–834. https://doi.org/10.3852/13-340
  • Halling RE, Nuhn M, Fechner NA, Osmundson TW, Soytong K, Arora D, Hibbett DS, Binder M (2012) Sutorius: a new genus for Boletus eximius. Mycologia 104(4): 951–961. https://doi.org/10.3852/11-376
  • Horak E (2011) Revision of Malaysian Species of Boletales s.l. (Basidiomycota) Described by Corner EJH (1972, 1974). Forest Research Institute and Ministry of Natural Resources and Environment, Malaysia, 1–283.
  • Hosen MI, Feng B, Wu G, Zhu XT, Li YC, Yang ZL (2013) Borofutus, a new genus of Boletaceae from tropical Asia: phylogeny, morphology and taxonomy. Fungal Diversity 58: 215–226. https://doi.org/10.1007/s13225-012-0211-8
  • Katoh K, Standley DM (2013) MAFFT Multiple sequence alignment software version 7: improvements in performance and usability. Molecular Biology and Evolution 30: 772–780. https://doi.org/10.1093/molbev/mst010
  • Kornerup A, Wanscher JH (1978) Methuen Handbook of Colour. 3rd ed. Eyre Methuen Ltd, London, 1–252.
  • Lebel T, Orihara T, Maekawa N (2012) The sequestrate genus Rosbeeva T. Lebel & Orihara gen. nov. (Boletaceae) from Australasia and Japan: new species and new combinations. Fungal Diversity 52: 49–71. https://doi.org/10.1007/s13225-011-0109-x
  • Li YC, Ortiz-Santana B, Zeng NK, Feng B (2014) Molecular phylogeny and taxonomy of the genus Veloporphyrellus. Mycologia 106(2): 291–306. https://doi.org/10.3852/106.2.291
  • Luangviriyasaeng V (2003) Eucalypt planting in Thailand. In: Turnbull JW (Ed.) Eucalypts in Asia.Proceedings of an international conference held in Zhanjiang, Guangdong, People’s Republic of China, 7–11 April 2003. ACIAR Proceedings no. 111. Australian Centre for International Agricultural Research, Canberra, 28–31.
  • Matheny PB (2005) Improving phylogenetic inference of mushrooms with RPB1 and RPB2 nucleotide sequences (Inocybe; Agaricales). Molecular Phylogenetics and Evolution 35: 1–20. https://doi.org/10.1016/j.ympev.2004.11.014
  • Miller MA, Holder MT, Vos R, Midford PE, Liebowitz T, Chan L, Hoover P, Warnow T (2009) The CIPRES portals. CIPRES. Available at: http://www.phylo.org/portal2/home
  • Neves MA, Binder M, Halling R, Hibbett D, Soytong K (2012) The phylogeny of selected Phylloporus species inferred from NUC-LSU and ITS sequences, and descriptions of new species from the Old World. Fungal Diversity 55(1): 109–123. https://doi.org/10.1007/s13225-012-0154-0
  • Orihara T, Lebel T, Ge Z-W, Smith ME, Maekawa N (2016) Evolutionary history of the sequestrate genus Rossbeevera (Boletaceae) reveals a new genus Turmalinea and highlights the utility of ITS minisatellite-like insertions for molecular identification. Persoonia 37: 173–198. https://doi.org/10.3767/003158516X691212
  • Orihara T, Smith ME, Shimomura N, Iwase K, Maekawa N (2012) Diversity and systematics of the sequestrate genus Octaviania in Japan: two new subgenera and eleven new species. Persoonia 28: 85–112. https://doi.org/10.3767/003158512X650121
  • Pegler DN, Young TWK (1989) Rhodactina himalayensis gen. et sp. nov. (Gautieriaceae) from India. Opera Botanica 100: 201–206.
  • Raspé O, Vadthanarat S, De Kesel A, Degreef J, Hyde KD, Lumyong S (2016) Pulveroboletus fragrans, a new Boletaceae species from Northern Thailand, with a remarkable aromatic odor. Mycological Progress 15: 38. https://doi.org/10.1007/s11557-016-1179-7
  • Rehner SA, Buckley E (2005) A Beauveria phylogeny inferred from nuclear ITS and EF1-α sequences: evidence for cryptic diversification and links to Cordyceps teleomorphs. Mycologia 97: 84–98.
  • Smith ME, Amses KR, Elliott TF, Obase K, Aime MC, Henkel TW (2015) New sequestrate fungi from Guyana: Jimtrappea guyanensis gen. sp. nov., Castellanea pakaraimophila gen. sp. nov., and Costatisporus cyanescens gen. sp. nov. (Boletaceae, Boletales). IMA Fungus 6(2): 297–317. https://doi.org/10.5598/imafungus.2015.06.02.03
  • Thiers B (continuously updated) Index Herbariorum: A Global Directory of Public Herbaria and Associated Staff. New York Botanical Garden’s Virtual Herbarium. http://sweetgum.nybg.org/science/ih/
  • Wu G, Feng B, Xu J, Zhu XT, Li YC, Zeng NK, Hosen MI, Yang ZL (2014) Molecular phylogenetic analyses redefine seven major clades and reveal 22 new generic clades in the fungal family Boletaceae. Fungal Diversity 69: 93–115. https://doi.org/10.1007/s13225-014-0283-8
  • Yang ZL, Trappe JM, Binder M, Sanmee R, Lumyong P, Lumyong S (2006) The sequestrate genus Rhodactina (Basidiomycota, Boletales) in northern Thailand. Mycotaxon 96: 133–140.
  • Zhu XT, Wu G, Zhao K, Halling RE, Yang ZL (2015) Hourangia, a new genus of Boletaceae to accommodate Xerocomus cheoi and its allied species. Mycological Progress 14: 37. https://doi.org/10.1007/s11557-015-1060-0
login to comment