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Lücking R, Hawksworth DL. Formal description of sequence-based voucherless Fungi: promises and pitfalls, and how to resolve them. IMA Fungus 2018; 9:143-166. [PMID: 30018876 PMCID: PMC6048566 DOI: 10.5598/imafungus.2018.09.01.09] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Accepted: 05/15/2018] [Indexed: 11/25/2022] Open
Abstract
There is urgent need for a formal nomenclature of sequence-based, voucherless Fungi, given that environmental sequencing has accumulated more than one billion fungal ITS reads in the Sequence Read Archive, about 1,000 times as many as fungal ITS sequences in GenBank. These unnamed Fungi could help to bridge the gap between 115,000 to 140,000 currently accepted and 2.2 to 3.8 million predicted species, a gap that cannot realistically be filled using specimen or culture-based inventories. The Code never aimed at placing restrictions on the nature of characters chosen for taxonomy, and the requirement for physical types is now becoming a constraint on the advancement of science. We elaborate on the promises and pitfalls of sequence-based nomenclature and provide potential solutions to major concerns of the mycological community. Types of sequence-based taxa, which by default lack a physical specimen or culture, could be designated in four alternative ways: (1) the underlying sample ('bag' type), (2) the DNA extract, (3) fluorescent in situ hybridization (FISH), or (4) the type sequence itself. Only (4) would require changes to the Code and the latter would be the most straightforward approach, complying with three of the five principal functions of types better than physical specimens. A fifth way, representation of the sequence in an illustration, has been ruled as unacceptable in the Code. Potential flaws in sequence data are analogous to flaws in physical types, and artifacts are manageable if a stringent analytical approach is applied. Conceptual errors such as homoplasy, intragenomic variation, gene duplication, hybridization, and horizontal gene transfer, apply to all molecular approaches and cannot be used as a specific argument against sequence-based nomenclature. The potential impact of these phenomena is manageable, as phylogenetic species delimitation has worked satisfactorily in Fungi. The most serious shortcoming of sequence-based nomenclature is the likelihood of parallel classifications, either by describing taxa that already have names based on physical types, or by using different markers to delimit species within the same lineage. The probability of inadvertently establishing sequence-based species that have names available is between 20.4 % and 1.5 % depending on the number of globally predicted fungal species. This compares favourably to a historical error rate of about 30 % based on physical types, and this rate could be reduced to practically zero by adding specific provisions to this approach in the Code. To avoid parallel classifications based on different markers, sequence-based nomenclature should be limited to a single marker, preferably the fungal ITS barcoding marker; this is possible since sequence-based nomenclature does not aim at accurate species delimitation but at naming lineages to generate a reference database, independent of whether these lineages represent species, closely related species complexes, or infraspecies. We argue that clustering methods are inappropriate for sequence-based nomenclature; this approach must instead use phylogenetic methods based on multiple alignments, combined with quantitative species recognition methods. We outline strategies to obtain higher-level phylogenies for ITS-based, voucherless species, including phylogenetic binning, 'hijacking' species delimitation methods, and temporal banding. We conclude that voucherless, sequence-based nomenclature is not a threat to specimen and culture-based fungal taxonomy, but a complementary approach capable of substantially closing the gap between known and predicted fungal diversity, an approach that requires careful work and high skill levels.
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Affiliation(s)
- Robert Lücking
- Botanischer Garten und Botanisches Museum, Freie Universität Berlin, Königin-Luise-Strasse 6–8, 14195 Berlin, Germany
| | - David L. Hawksworth
- Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK; and Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Surrey TW9 3DS, UK; Jilin Agricultural University, Changchun, Jilin Province,130118 China
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Zamora JC, Svensson M, Kirschner R, Olariaga I, Ryman S, Parra LA, Geml J, Rosling A, Adamčík S, Ahti T, Aime MC, Ainsworth AM, Albert L, Albertó E, García AA, Ageev D, Agerer R, Aguirre-Hudson B, Ammirati J, Andersson H, Angelini C, Antonín V, Aoki T, Aptroot A, Argaud D, Sosa BIA, Aronsen A, Arup U, Asgari B, Assyov B, Atienza V, Bandini D, Baptista-Ferreira JL, Baral HO, Baroni T, Barreto RW, Beker H, Bell A, Bellanger JM, Bellù F, Bemmann M, Bendiksby M, Bendiksen E, Bendiksen K, Benedek L, Bérešová-Guttová A, Berger F, Berndt R, Bernicchia A, Biketova AY, Bizio E, Bjork C, Boekhout T, Boertmann D, Böhning T, Boittin F, Boluda CG, Boomsluiter MW, Borovička J, Brandrud TE, Braun U, Brodo I, Bulyonkova T, Burdsall HH, Buyck B, Burgaz AR, Calatayud V, Callac P, Campo E, Candusso M, Capoen B, Carbó J, Carbone M, Castañeda-Ruiz RF, Castellano MA, Chen J, Clerc P, Consiglio G, Corriol G, Courtecuisse R, Crespo A, Cripps C, Crous PW, da Silva GA, da Silva M, Dam M, Dam N, Dämmrich F, Das K, Davies L, De Crop E, De Kesel A, De Lange R, De Madrignac Bonzi B, dela Cruz TEE, Delgat L, Demoulin V, Desjardin DE, Diederich P, Dima B, Dios MM, Divakar PK, Douanla-Meli C, Douglas B, Drechsler-Santos ER, Dyer PS, Eberhardt U, Ertz D, Esteve-Raventós F, Salazar JAE, Evenson V, Eyssartier G, Farkas E, Favre A, Fedosova AG, Filippa M, Finy P, Flakus A, Fos S, Fournier J, Fraiture A, Franchi P, Molano AEF, Friebes G, Frisch A, Fryday A, Furci G, Márquez RG, Garbelotto M, García-Martín JM, Otálora MAG, Sánchez DG, Gardiennet A, Garnica S, Benavent IG, Gates G, da Cruz Lima Gerlach A, Ghobad-Nejhad M, Gibertoni TB, Grebenc T, Greilhuber I, Grishkan B, Groenewald JZ, Grube M, Gruhn G, Gueidan C, Gulden G, Gusmão LFP, Hafellner J, Hairaud M, Halama M, Hallenberg N, Halling RE, Hansen K, Harder CB, Heilmann-Clausen J, Helleman S, Henriot A, Hernandez-Restrepo M, Herve R, Hobart C, Hoffmeister M, Høiland K, Holec J, Holien H, Hughes K, Hubka V, Huhtinen S, Ivančević B, Jagers M, Jaklitsch W, Jansen A, Jayawardena RS, Jeppesen TS, Jeppson M, Johnston P, Jørgensen PM, Kärnefelt I, Kalinina LB, Kantvilas G, Karadelev M, Kasuya T, Kautmanová I, Kerrigan RW, Kirchmair M, Kiyashko A, Knapp DG, Knudsen H, Knudsen K, Knutsson T, Kolařík M, Kõljalg U, Košuthová A, Koszka A, Kotiranta H, Kotkova V, Koukol O, Kout J, Kovács GM, Kříž M, Kruys Å, Kučera V, Kudzma L, Kuhar F, Kukwa M, Arun Kumar TK, Kunca V, Kušan I, Kuyper TW, Lado C, Læssøe T, Lainé P, Langer E, Larsson E, Larsson KH, Laursen G, Lechat C, Lee S, Lendemer JC, Levin L, Lindemann U, Lindström H, Liu X, Hernandez RCL, Llop E, Locsmándi C, Lodge DJ, Loizides M, Lőkös L, Luangsa-ard J, Lüderitz M, Lumbsch T, Lutz M, Mahoney D, Malysheva E, Malysheva V, Manimohan P, Marin-Felix Y, Marques G, Martínez-Gil R, Marson G, Mata G, Matheny PB, Mathiassen GH, Matočec N, Mayrhofer H, Mehrabi M, Melo I, Mešić A, Methven AS, Miettinen O, Romero AMM, Miller AN, Mitchell JK, Moberg R, Moreau PA, Moreno G, Morozova O, Morte A, Muggia L, González GM, Myllys L, Nagy I, Nagy LG, Neves MA, Niemelä T, Nimis PL, Niveiro N, Noordeloos ME, Nordin A, Noumeur SR, Novozhilov Y, Nuytinck J, Ohenoja E, Fiuza PO, Orange A, Ordynets A, Ortiz-Santana B, Pacheco L, Pál-Fám F, Palacio M, Palice Z, Papp V, Pärtel K, Pawlowska J, Paz A, Peintner U, Pennycook S, Pereira OL, Daniëls PP, Pérez-De-Gregorio Capella MÀ, del Amo CMP, Gorjón SP, Pérez-Ortega S, Pérez-Vargas I, Perry BA, Petersen JH, Petersen RH, Pfister DH, Phukhamsakda C, Piątek M, Piepenbring M, Pino-Bodas R, Esquivel JPP, Pirot P, Popov ES, Popoff O, Álvaro MP, Printzen C, Psurtseva N, Purahong W, Quijada L, Rambold G, Ramírez NA, Raja H, Raspé O, Raymundo T, Réblová M, Rebriev YA, de Dios Reyes García J, Ripoll MÁR, Richard F, Richardson MJ, Rico VJ, Robledo GL, Barbosa FR, Rodriguez-Caycedo C, Rodriguez-Flakus P, Ronikier A, Casas LR, Rusevska K, Saar G, Saar I, Salcedo I, Martínez SMS, Montoya CAS, Sánchez-Ramírez S, Sandoval-Sierra JV, Santamaria S, Monteiro JS, Schroers HJ, Schulz B, Schmidt-Stohn G, Schumacher T, Senn-Irlet B, Ševčíková H, Shchepin O, Shirouzu T, Shiryaev A, Siepe K, Sir EB, Sohrabi M, Soop K, Spirin V, Spribille T, Stadler M, Stalpers J, Stenroos S, Suija A, Sunhede S, Svantesson S, Svensson S, Svetasheva TY, Świerkosz K, Tamm H, Taskin H, Taudière A, Tedebrand JO, Lahoz RT, Temina M, Thell A, Thines M, Thor G, Thüs H, Tibell L, Tibell S, Timdal E, Tkalčec Z, Tønsberg T, Trichies G, Triebel D, Tsurykau A, Tulloss RE, Tuovinen V, Sosa MU, Urcelay C, Valade F, Garza RV, van den Boom P, Van Vooren N, Vasco-Palacios AM, Vauras J, Velasco Santos JM, Vellinga E, Verbeken A, Vetlesen P, Vizzini A, Voglmayr H, Volobuev S, von Brackel W, Voronina E, Walther G, Watling R, Weber E, Wedin M, Weholt Ø, Westberg M, Yurchenko E, Zehnálek P, Zhang H, Zhurbenko MP, Ekman S. Considerations and consequences of allowing DNA sequence data as types of fungal taxa. IMA Fungus 2018; 9:167-175. [PMID: 30018877 PMCID: PMC6048565 DOI: 10.5598/imafungus.2018.09.01.10] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 05/21/2018] [Indexed: 11/11/2022] Open
Abstract
Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.
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Affiliation(s)
- Juan Carlos Zamora
- Museum of Evolution, Uppsala University, Norbyvägen 16, 75236 Uppsala, Sweden
| | - Måns Svensson
- Museum of Evolution, Uppsala University, Norbyvägen 16, 75236 Uppsala, Sweden
| | | | - Ibai Olariaga
- Universidad Rey Juan Carlos, 28933 Móstoles, Madrid, Spain
| | - Svengunnar Ryman
- Museum of Evolution, Uppsala University, Norbyvägen 16, 75236 Uppsala, Sweden
| | | | - József Geml
- Naturalis Biodiversity Center, Vondellaan 55, 2332AA Leiden, The Netherlands
| | - Anna Rosling
- Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 75236 Uppsala, Sweden
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- Museum of Evolution, Uppsala University, Norbyvägen 16, 75236 Uppsala, Sweden
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Lücking R, Kirk PM, Hawksworth DL. Sequence-based nomenclature: a reply to Thines et al. and Zamora et al. and provisions for an amended proposal "from the floor" to allow DNA sequences as types of names. IMA Fungus 2018; 9:185-198. [PMID: 30018879 PMCID: PMC6048568 DOI: 10.5598/imafungus.2018.09.01.12] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 06/08/2018] [Indexed: 02/07/2023] Open
Abstract
We reply to two recently published, multi-authored opinion papers by opponents of sequence-based nomenclature, namely Zamora et al. (IMA Fungus9: 167-175,2018) and Thines et al. (IMA Fungus9: 177-183, 2018). While we agree with some of the principal arguments brought forward by these authors, we address misconceptions and demonstrate that some of the presumed evidence presented in these papers has been wrongly interpreted. We disagree that allowing sequences as types would fundamentally alter the nature of types, since a similar nature of abstracted features as type is already allowed in the Code (Art. 40.5), namely an illustration. We also disagree that there is a high risk of introducing artifactual taxa, as this risk can be quantified at well below 5 %, considering the various types of high-throughput sequencing errors. Contrary to apparently widespread misconceptions, sequence-based nomenclature cannot be based on similarity-derived OTUs and their consensus sequences, but must be derived from rigorous, multiple alignment-based phylogenetic methods and quantitative, single-marker species recognition algorithms, using original sequence reads; it is therefore identical in its approach to single-marker studies based on physical types, an approach allowed by the Code. We recognize the limitations of the ITS as a single fungal barcoding marker, but point out that these result in a conservative approach, with "false negatives" surpassing "false positives"; a desirable feature of sequence-based nomenclature. Sequence-based nomenclature does not aim at accurately resolving species, but at naming sequences that represent unknown fungal lineages so that these can serve as a means of communication, so ending the untenable situation of an exponentially growing number of unlabeled fungal sequences that fill online repositories. The risks are outweighed by the gains obtained by a reference library of named sequences spanning the full array of fungal diversity. Finally, we elaborate provisions in addition to our original proposal to amend the Code that would take care of the issues brought forward by opponents to this approach. In particular, taking up the idea of the Candidatus status of invalid, provisional names in prokaryote nomenclature, we propose a compromise that would allow valid publication of voucherless, sequence-based names in a consistent manner, but with the obligate designation as "nom. seq." (nomen sequentiae). Such names would not have priority over specimen- or culture-based names unless either epitypified with a physical type or adopted for protection on the recommendation of a committee of the International Commission on the Taxonomy of Fungi following evaluation based on strict quality control of the underlying studies based on established rules or recommendations.
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Affiliation(s)
- Robert Lücking
- Botanischer Garten und Botanisches Museum, Freie Universität Berlin, Königin-Luise-Straße 6-8, D-14195 Berlin, Germany
| | - Paul M. Kirk
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; Biodiversity Informatics & Spatial Analysis, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK
| | - David L. Hawksworth
- Comparative Plant and Fungal Biology, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3DS, UK; Department of Life Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK; Jilin Agricultural University, Chanchung, Jilin province, 130118 China
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