The rules that govern the scientific naming of algae, fungi, and plants are revised at the Nomenclature Section of an International Botanical Congress (IBC). This edition of the International Code of Nomenclature for algae, fungi, and plants embodies the decisions of the XIX IBC, which took place in Shenzhen, China in July, 2017. This Shenzhen Code supersedes the Melbourne Code (McNeill & al. in Regnum Veg. 154. 2012), published six years ago after the XVIII IBC in Melbourne, Australia, and like its five predecessors, it is written entirely in (British) English. The Melbourne Code was translated into Chinese, French, Italian, Japanese, Korean, Portuguese, Spanish, and Turkish; it is anticipated that the Shenzhen Code, too, will become available in several languages. In questions about the meaning of provisions in translated editions of this Code, the English edition is definitive.

Amending the Code – from Melbourne to Shenzhen

Altogether, 397 numbered proposals to amend the Melbourne Code were published in Taxon, the journal of the International Association for Plant Taxonomy (IAPT), between February 2014 and December 2016. A synopsis of the proposals, with comments by the Rapporteur-général and Vice-rapporteur, appeared in February 2017 (Turland & Wiersema in Taxon 66: 217–274. 2017) and served as the basis for the preliminary guiding vote cast by members of the IAPT, authors of the proposals, and members of the Permanent Nomenclature Committees, as specified in Division III of the Melbourne Code. Tabulation of the preliminary guiding vote (“mail vote”) was handled at the central office of the IAPT in Bratislava by Eva Senková and Matúš Kempa. These results were published as an online “fast-track” article on 26 June 2017 ahead of the Nomenclature Section (Turland & al. in Taxon 66: 995–1000. 2017).

The Nomenclature Section met from Monday to Friday, 17–21 July 2017 in Lecture Hall 502, 5th Floor, Peking University HSBC Business School, University Town, Nanshan District, Shenzhen 518055, Guangdong, China (and was followed, from 23–29 July, by the main part of the IBC at the Shenzhen Convention & Exhibition Center). There were 155 registered members in attendance, carrying 427 institutional votes in addition to one personal vote each, making a total of 582 possible votes. The Section officers, previously appointed in conformity with Division III of the Melbourne Code, were Sandra (Sandy) Knapp (President), Nicholas (Nick) Turland (Rapporteur-général), John Wiersema (Vice-rapporteur), and Yun-Fei Deng and Li Zhang (Recorders). As in Melbourne, the Recorders were expertly assisted by Anna Monro. The discussions of the Section were conducted in English.

Each Nomenclature Section is entitled to define its own procedural rules within the limits set by the Code. This time, before discussions began on proposals to amend the Code, the Section adopted the relevant procedural rules set out in the proposed new Division III, which was formally discussed and voted on later in the Section. These procedures are detailed in the Report of Congress action mentioned in the next paragraph. Of the 397 published proposals to amend the Melbourne Code, 113 were accepted and 103 were referred to the Editorial Committee; an additional seven were accepted from among 16 new proposals made from the floor of the Section.

The rules of the Shenzhen Code became effective immediately upon acceptance of the resolution, moved on behalf of the Section at the closing plenary session of the XIX IBC on 29 July 2017, that the decisions and appointments of the Nomenclature Section be approved. The “Report of Congress action on nomenclature proposals”, detailing the committees and officers appointed by the IBC and the results of the proposals, was published as an online “fast-track” article on 14 August 2017 (Turland & al. in Taxon 66: 1234–1245. 2017). The full, day-to-day proceedings of the Section will form a separate publication, planned for late 2018 or 2019. The audio recordings of the Section were transcribed by Pacific Transcription, Indooroopilly, Australia, between November 2017 and January 2018, co-ordinated by Anna Monro and financially supported by the IAPT. The transcription will be edited into the usual indirect speech format of previous Nomenclature Section Reports (see, e.g., Flann & al. in PhytoKeys 41: 1–289. 2014 [Melbourne] and Flann & al. in PhytoKeys 45: 1–341. 2015 [Vienna]).

The Nomenclature Section also elected the Editorial Committee for the Shenzhen Code. As is traditional, and in accordance with Div. III Prov. 7.4, the Nominating Committee proposed members of the Section who were physically present there to serve on the Editorial Committee, with the Rapporteur-général and Vice-rapporteur serving as the Chair and Secretary, respectively. The Editorial Committee was increased in size from the previous 14 to the present 16 members to ensure representation from each continent, to include expertise in the main groups of organisms covered by the Code (vascular plants, bryophytes, fungi, and algae, both extant and fossil), and to improve gender balance (there are now three women on the Committee, compared with one previously).

As usual, the Editorial Committee had a mandate to deal with matters specifically referred to it, to incorporate into the new Code the changes agreed by the Section, to clarify any ambiguous wording so long as the meaning is not changed, to ensure consistency and optimal placement of provisions while retaining the present numbering insofar as possible, and to add (or remove) Examples to best illustrate the provisions.

A draft of the main body of the Shenzhen Code, incorporating the changes decided by the Section, was prepared between August and October 2017 by eight members of the Editorial Committee, as follows: Barrie (Art. 16–28), Greuter (Art. 60–62, with restructuring of Art. 60), May (Chapter F), McNeill (Art. 51–58), Monro (Art. 46–50, Chapter H), Price (Glossary), Turland (Preamble, Principles, Art. 29–45, Division III), and Wiersema (Art. 1–14). This draft of the Code was distributed by e-mail to the full Committee on 16 October 2017. It was updated according to comments subsequently received from the members and was used at the Editorial Committee meeting as the basis for discussion.

The full Editorial Committee met from 11–15 December 2017 at the Botanischer Garten und Botanisches Museum Berlin, Germany, for five days of hard work: scrutinizing the entire Code, reviewing not only the changes made in Shenzhen and the Examples referred to the Committee, but also reviewing the existing wording and finding new Examples where necessary. Essential details of the new Chapter F were decided, as was how to incorporate protected names (Art. F.2, formerly Art. 14.13) into the Appendices. It was an intense but highly productive week.

Following the meeting, a revised draft of the Shenzhen Code was completed and distributed to all Editorial Committee members on 13 January 2018 for further scrutiny. After a multitude of comments and some five weeks of e-mail discussions, a near-final draft of the Code was compiled and circulated to all members on 21 February. After a final round of checking and correcting, the finished text was sent to Franz Stadler, the Production Editor of Regnum Vegetabile, on 26 March to begin the formatting and page layout. The Index of scientific names, compiled by Knapp and Turland, and the Subject index, compiled by Monro, followed shortly afterward. After formatting, page layout, proofreading, and final corrections, the Shenzhen Code was sent to Koeltz Botanical Books for publication.

Names of organisms treated as fungi

The most extreme change to the Code resulting from the Shenzhen IBC was the Nomenclature Section’s decision that future proposals to amend the Code relating solely to names of organisms treated as fungi will be decided exclusively by the Nomenclature Session of an International Mycological Congress (IMC), the decisions of which will be binding on the next IBC. However, the IMC will have no authority to amend any other provisions of the Code. If there is any doubt as to whether proposals to amend the Code relate solely to names of fungi, the General Committee in consultation with the Nomenclature Committee for Fungi has the final say. These new rules were developed by the Special Subcommittee on Governance of the Code with respect to Fungi (May & al. in Taxon 65: 918–920; May in Taxon 65: 921–925. 2016), established by the Melbourne IBC of 2011 to report to the Shenzhen IBC, and are included in the new Division III, Provisions for Governance of the Code, which is discussed below.

Fungal provisions now in Chapter F

A significant amendment to the proposal of the Special Subcommittee on Governance of the Code with respect to Fungi was accepted at the Section, namely to bring together all the provisions of the Code that deal solely with names of organisms treated as fungi into a special Chapter, which has been called Chapter F (the “F” standing, of course, for fungi), so that the IMC has exclusive authority over this Chapter and the IBC has exclusive authority over the rest of the Code. Chapter F immediately follows Art. 62 and consists of nine Articles, numbered Art. F.1–F.9 (paralleling Art. H.1–H.12 on the names of hybrids in Chapter H), with the Key to the re-numbering of Articles, Notes, and Recommendations on p. xxx showing which provisions in the Melbourne Code have been moved to Chapter F and which are new. Art. F.1 concerns the nomenclatural starting-point for fungi, extracted from Art. 13.1. Art. F.2 permits names of fungi, submitted as lists, to be protected and included in the Appendices of the Code (Art. 14.13 of the Melbourne Code). In this Article, the term “protected” was introduced in Shenzhen along with an expanded concept that includes lichen-forming fungi and treats protected names as conserved against competing unlisted synonyms and homonyms. Art. F.3 concerns sanctioned names and includes the whole of the former Art. 15, also drawing together some material on sanctioning previously included in other Articles. The sanctioning works formerly mentioned under starting-points in Art. 13.1 (in which they had ceased to be starting-points in the Sydney Code of 1983) have been moved to Art. F.3.1. A sanctioned name may be indicated by adding “: Fr.” or “: Pers.” to a formal citation, and there is now, under Rec. F.3A.1, an alternative means of indicating them by adding “nom. sanct.” (nomen sanctionatum) to the citation. Art. F.4 rules on the rank-denoting term “tribus” in Fries’s Systema mycologicum and is the former Art. 37.9. Art. F.5 concerns registration of fungal names and includes the former Art. 42. In addition to the requirement to register nomenclatural novelties, starting on 1 January 2019 designation of a lectotype, neotype, or epitype will require citation of an identifier issued by a recognized repository (Art. F.5.4). Art. F.6 and F.7 concern rejection of names, where Art. F.6 is a new rule that a fungal name published on or after 1 January 2019 is illegitimate if it is a later homonym of a prokaryotic or protozoan name. Art. F.7 is the former Art. 56.3, permitting names of fungi, submitted as lists, to be rejected and included in the Appendices of the Code, although as yet no such lists of names have been approved. Art. F.8 is the former Art. 59 on names of fungi with a pleomorphic life cycle, and Art. F.9 is the former Art. 60.13 on orthography of epithets of fungal names derived from the generic name of an associated organism. Comprehensive re-numbering of the provisions from Art. 15 onward has been avoided in this edition of the Code by retaining for the sake of clarity and continuity “Article 15” and “Article 59” as headings in the regular sequence, but with cross-references to Chapter F to which their content has been transferred.

The introduction to Chapter F includes an emphatic reminder that most of the rest of the Code applies to names of fungi just as much as it does to names of algae and plants, and that Chapter F is certainly not the only part of the Code relevant to mycologists. An annotated list of particularly relevant provisions in other parts of the Code is provided.

Because Chapter F may be amended by either or both of the International Mycological Congresses in 2018 and 2022, mycologists should always consult the online version of the Code, where the amendments will be incorporated in such a way that it is clear that they originated from a specific IMC.

Governance of the Code – a new Division III

The second major change to the Code accepted at the Shenzhen IBC is the replacement of Division III, the Provisions for Governance of the Code, with an almost completely new and much-expanded version. This was developed by the Special Committee on By-laws for the Nomenclature Section (Knapp & al. in Taxon 65: 661–664; 665–669. 2016) established by the Melbourne IBC to report to Shenzhen. The Committee decided that the operating procedures of the Nomenclature Section and, during the period between IBCs, of the Permanent Nomenclature Committees, were largely based on tradition, partly recorded in various reports published mostly in Taxon, but partly also surviving in the memories of individuals (e.g. the Rapporteur-général) from one IBC to another. It was decided that, to protect this knowledge, stabilize practice over time, and to make nomenclature less arcane, these traditions should be crystallized into actual provisions of the Code, in an updated and expanded Division III. The majority of the new Division III reflects current practice, although some procedures are new, notably those concerning institutional votes (Prov. 3), which were developed by the Special Committee on Institutional Votes (Funk & Turland in Taxon 65: 1449–1454. 2016) and those on proposals to amend the Code relating solely to names of fungi (Prov. 8), developed by the Special Subcommittee on Governance of the Code with respect to Fungi, as mentioned above. Prov. 1 consists of general provisions on governance, Prov. 2 concerns proposals to amend the Code, Prov. 4 defines the roles and responsibilities of the Nomenclature Section, Prov. 5 governs procedure and voting at the Nomenclature Section, Prov. 6 specifies the reports that will appear after an IBC, and Prov. 7 details the nine Permanent Nomenclature Committees and their membership, functions, and procedural rules. There are two new Permanent Nomenclature Committees: the Committee on Institutional Votes and the Registration Committee. The Committees for Vascular Plants, Bryophytes, Fungi, Algae, and Fossils are now collectively known as “Specialist Committees” and what were previously called Special Committees (established by one IBC to report to the next, with a specific mandate) become “Special-purpose Committees”.

Other new rules in Division III include the method by which the Bureau of Nomenclature is appointed. The President of the Nomenclature Section is now elected by the General Committee and the Vice-rapporteur is appointed by the Rapporteur-général and approved by the General Committee. This makes the General Committee responsible for these officers instead of the Organizing Committee of an IBC, the members of which do not necessarily have nomenclatural experience.

Governance of fungal provisions

As specified in Division III, the IMC operates along much the same principles as the IBC, except that it has a Fungal Nomenclature Session (not Section), with a Fungal Nomenclature Bureau comprising a Chair, Secretary, and Deputy Secretary, who are equivalent to President, Rapporteur-général, and Vice-rapporteur, respectively. A preliminary guiding vote is organized prior to an IMC, but there are no institutional votes at a Fungal Nomenclature Session. The Rapporteur-général is invited to attend the Session as a non-voting advisor. The Session has its own Nominating Committee and elects the Secretary of the Fungal Nomenclature Bureau for the next IMC and the members of the Nomenclature Committee for Fungi which, in turn, nominates a member of the Editorial Committee. Relevant publications concerning proposals to amend Chapter F of the Code are published in the journal IMA Fungus instead of Taxon. The relevant Provisions of Division III are Prov. 1.4 and footnote, 4.13, 7.1(g), 7.4, 7.8, 7.10, 7.14, and 8.1–8.12.

Note that for individual proposals concerning fungal names (including names of fossil fungi) there is no change to the procedure to conserve or reject names or suppress works, nor to the procedure to request binding decisions. All such individual proposals or requests that concern names of fungi must continue to be submitted to the General Committee, which will refer them for examination to the relevant specialist committees, and submission is currently effected by publication in Taxon, not in IMA Fungus. However, lists of names proposed for protection under Art. F.2.1 or rejection under Art. F.7.1 must be submitted to the General Committee by publication in IMA Fungus.

Registration of algal and plant names

The third major change to the Code in Shenzhen was the acceptance of most of the proposals developed by the Special Committee on Registration of Algal and Plant Names (including fossils) (Barkworth & al. in Taxon 65: 656–658; 670–672. 2016). These are now included in Art. 42 (with the content of the Melbourne Code Art. 42, which does not concern algal or plant names, transferred to Chapter F, under Art. F.5). The mechanism by which registration of algal and plant names could operate is laid out in Art. 42.1–42.3, although such registration is not yet a requirement for valid publication and cannot become so before the XX IBC in Rio de Janeiro in 2023. A Registration Committee has been established to assist with the design, implementation, monitoring, and functioning of nomenclatural repositories and to advise the General Committee (see Div. III Prov. 7).

Other amendments to the Code

Numerous other, smaller changes to the Code were made in Shenzhen, and they are discussed below. The following list is not intended to cover every change, but it includes the more important items.

The rules in Art. 6 on defining the status of a name as either a replacement name or the name of a new taxon have been revised. While a replacement name is normally proposed as an explicit substitute (avowed substitute) for an earlier name (Art. 6.11), a name not explicitly proposed as a substitute may nevertheless be a replacement name (Art. 6.12), or be treated as either a replacement name or the name of a new taxon (Art. 6.13). An incorrect statement about the status of a name, e.g. name of a new taxon, new combination, or replacement name, does not preclude its valid publication with a different status (Art. 6.14).

Art. 7.5 has been refined to make clearer how a name that is illegitimate because it was nomenclaturally superfluous when published (Art. 52) is typified. The clause concerning a subordinate taxon not including the intended type of the illegitimate name has been separated as Art. 7.6.

Under Art. 8.2, the definition of a gathering, which was only implicit in the Melbourne Code, has been made explicit in a footnote.

The definition of a holotype in Art. 9.1 has been amended to show that a holotype is the one specimen or illustration indicated by the author as the type or, when not so indicated, used by the author. For older names, where no type was indicated, it is often impossible to be sure that the author used only a single specimen or illustration, because specimens may have been in the author’s possession that have since been lost or destroyed. Moreover, mention of a single specimen or illustration in the protologue is not to be interpreted as indication of the type, except under Art. 40.3, which applies only for the purpose of Art. 40.1, i.e. only to names published on or after 1 January 1958, and ceases to apply on 1 January 1990 when one must explicitly designate a type using the word “typus” or “holotypus” or an equivalent (Art. 40.6).

Art. 9.4 has been amended to make it clear that original material includes illustrations published as part of the protologue. Also, specimens and illustrations are original material if the author associated them with the taxon and they were available to the author at the appropriate time. This replaces the rather awkward requirement, first introduced in the Tokyo Code of 1994, to show that the validating description or diagnosis was based on certain specimens or illustrations in order for them to qualify as original material.

The notion of “second-step” lectotypification or neotypification under Art. 9.17, where a first type designation is later found to refer to a single gathering but to more than one specimen, has been extended to apply also to epitypification.

Under Art. 9.19 of the Melbourne Code, a lectotype or neotype that was in serious conflict with the protologue could be superseded if another element was available that did not conflict. However, if all the elements of original material conflicted, the only options were to accept the consequent nomenclatural disruption or to propose the name for conservation with a conserved type. Under the amended Art. 9.19, a conflicting lectotype may be superseded only by a non-conflicting element; and when no such elements exist, a neotype may be designated.

Since 1 January 2001, Art. 9.23 has required use of the term “lectotypus” or “neotypus” or an equivalent for the designation of a lectotype or neotype. When designating an epitype, one must now use the term “epitypus” or an equivalent, and this is retroactive to 2001, which should not cause any problems because presumably all epitype designations must have used such a term since the concept first entered the Tokyo Code of 1994.

The Special Committee on Publications Using a Largely Mechanical Method of Selection of Types (Art. 10.5(b)) developed a set of proposals (McNeill & al. in Taxon 65: 1441–1442; 1443–1448. 2016) to deal with the old problem of type choices that used a largely mechanical method of selection, e.g. by authors following the American Code of Botanical Nomenclature (Arthur & al. in Bull. Torrey Bot. Club 34: 172–174. 1907). The proposals were accepted in Shenzhen. Under an amended Art. 10.5, such type choices are supersedable unless they have been “affirmed” by a subsequent selection of the same type not using such a method. Art. 10.6 defines “a largely mechanical method of selection”, and Art. 10.7 lays out the criteria by which it can be determined that an author used such a method.

Another change to Art. 10.5 was the deletion of the redundant clause (a), which concerned supersession of a type that seriously conflicted with the protologue. Either such an element is part of the protologue, and cannot therefore conflict with it, or otherwise supersession is already permitted by Art. 10.2.

The correct name for a taxon below the rank of genus could be determined under Art. 11.4 of the Melbourne Code, except when the resulting combination could not be validly published (because it would be a tautonym) or when it would be illegitimate (because it would be a later homonym). In such cases, there was no explicit guidance to determine the correct name. A new final sentence of Art. 11.4 now explains what is to be done, i.e. the final epithet of the next earliest legitimate name in the same rank is to be used, if available, or else a replacement name or the name of a new taxon may be published.

In Art. 14.3 a sentence has been added to rule that the application of conserved and rejected names of nothogenera is determined by a statement of parentage, not by the type, which such names do not have according to Art. H.9.1. The amendment was sparked by the case of ×Brassolaeliocattleya J. G. Fowler, which was recently proposed for conservation with that spelling against two earlier synonyms (Shaw in Taxon 65: 887. 2016).

Amendments to Art. 14.15 now permit the date of conservation of a name to be determined. The Code was previously silent as to this date, which can be important, especially in determining whether or not a name was nomenclaturally superfluous when published, because Art. 52.2(c) permits definite inclusion of type to be effected by citation of the previously conserved type. For names conserved from 1954 onward, conservation takes effect upon effective publication of the General Committee’s approval of the relevant conservation proposal, and this can be looked up in the online database of the Appendices of the Code ( This also applies to names protected under Art. F.2.

When the previous Editorial Committee was preparing the Melbourne Code, it shied away from universally changing the words “based on” to “formed from” in Art. 16–19, where this applied to an automatically typified suprageneric name formed from a generic name, e.g. Asteraceae formed from Aster, whereas “based on” could wrongly imply that Aster was the basionym of Asteraceae. Following a proposal referred to the Editorial Committee in Shenzhen, “based on” has been changed to “formed from” wherever appropriate throughout the Code.

Art. 16.3 has been amended so that names of algae at the ranks of division or phylum and subdivision or subphylum now end in phyta and phytina, respectively, instead of phycota and phycotina as in the Melbourne Code. However, for names of algae at the ranks of class and subclass, the endings phyceae and phycidae are still required.

The rules on electronic publication introduced at the Melbourne IBC have for the most part proved resilient. The most controversial aspect has perhaps been the use of preliminary page numbers in articles published online ahead of inclusion in a paginated online and/or print issue or volume of a journal. It had been suggested that preliminary page numbers were evidence of a “preliminary version that was, or is to be, replaced by a version that the publisher considers final”, which under Art. 30.2 of the Melbourne Code would not have been effectively published. In the Shenzhen Code, the emphasis has been shifted to the content of the electronic publication, which is ruled as excluding volume, issue, article, and page numbers (Art. 30.3), so that when there is evidence that the content is merely preliminary and was, or is to be, replaced by content that the publisher considers final, only the version with that final content is effectively published (Art. 30.2).

Rec. 30A.1, urging that preliminary and final versions of an electronic publication should be clearly indicated as such upon issue, has been reinforced with the advice that the phrase “Version of Record” should only be used to indicate a final version in which the content will not change.

The possibility for a publication to be suppressed under Art. 34.1 and included in App. I, so that new names at specified ranks in that publication are not validly published, has been extended to render ineffective any nomenclatural act in the publication that is associated with any name at the specified ranks. Art. 34.2 has also been amended to rule that suppression has retroactive effect.

Under Art. 36.3, alternative names published on or after 1 January 1953 are not validly published. The definition of alternative names has been amended so that, not only are they “two or more different names based on the same type … proposed simultaneously for the same taxon by the same author”, but they are names “accepted simultaneously … and accepted as alternatives by that author in the same publication”. If these criteria apply, none of these names, if new, is validly published.

Art. 38.4 permits binding decisions as to whether or not a name is validly published when it is doubtful whether a descriptive statement satisfies the requirement of Art. 38.1(a). It is now ruled that such binding decisions have retroactive effect.

As mentioned above under Art. 9.1 on holotypes, the second sentence of Art. 40.3 has been amended to make it clear that it applies only for the purpose of Art. 40.1, i.e. only for the indication of a type as a requirement for valid publication of the name of a new taxon of the rank of genus or below published on or after 1 January 1958. All the other Articles of Art. 40 were already explicitly limited by date and none applied to names published prior to 1958.

Art. 40.8 is new, and requires that, for names published on or after 1 January 2019, when the type is a culture, the protologue must include a statement that the culture is preserved in a metabolically inactive state.

Author citation has been dauntingly complicated for several editions of the Code, but a new Art. 46 Note 1 (following Art. 46.1) may make things a little easier by pointing out that “A name of a taxon is attributed to the author(s) of the publication in which it appears … unless one or more of the provisions of Art. 46 rules otherwise.”

Art. 46.4 rules that a validly published name taken up from a different “name” that was not validly published (i.e. a different designation) is to be attributed only to the authors of the validly published name. The scope of the rule has now been extended so that it no longer applies only to binary names and designations (i.e. at specific rank).

Art. 52.2 lists the ways in which definite inclusion of the type of a name may be effected for the purpose of Art. 52.1, concerning nomenclatural superfluity. One of these ways is “by citation of the name itself or any name homotypic at that time”. A new rule, Art. 52.3, rules that such citation of a name can be effected “by a direct and unambiguous reference to it”, which could be citation of its “original sequential number or exact diagnostic phrase name”, with the latter meaning, e.g., a Linnaean polynomial rather than its corresponding binomial. In addition, the new Art. 52 Note 3 points out that citation of a later isonym can in some cases be equivalent to citation of the name itself.

Art. 53.4 permits binding decisions as to whether or not names are to be treated as homonyms when it is doubtful whether they or their epithets are sufficiently alike to be confused. It is now ruled that such binding decisions have retroactive effect.

Cross-Code homonymy is dealt with under Art. 54.1, where two clauses are new. First, a name of an organism covered by and validly published under the International Code of Nomenclature for algae, fungi, and plants, but originally published for a taxon under another Code, is illegitimate if it is unavailable for use under that other Code, usually because of homonymy (Art. 54.1(b)(1)). Second, a name of a genus is treated as an illegitimate later homonym if it is spelled identically with an earlier intergeneric graft hybrid “name” established under the International Code of Nomenclature for Cultivated Plants (Art. 54.1(c)). Also concerning cross-Code homonymy, the new Art. F.6.1, mentioned under Chapter F above, rules that a fungal name published on or after 1 January 2019 is illegitimate if it is a later homonym of a prokaryotic or protozoan name.

Art. 55.4 is new, and explicitly allows a combination originally placed under a species or generic name that is a later homonym to be placed under the respective earlier homonym (where it is in effect the same combination) without any change to authorship or date of valid publication.

Art. 56.3 has been augmented to rule that the rejection of a name under either Art. 56 or F.7 takes effect on the date of effective publication of the General Committee’s approval of the relevant rejection proposal. As with conservation or protection proposals, this can be looked up in the online database of the Appendices of the Code.

Art. 57.2, which concerned a particular situation among names of pleomorphic fungi, was not transferred to Chapter F but was deleted as a result of a proposal accepted in Shenzhen.

In response to a proposal referred to the Editorial Committee in Shenzhen, Art. 60, dealing with orthography of names, has been restructured, arranging the rules into a more logical order and eliminating the two “back-door rules” whereby Art. 60.8 enforced Rec. 60G.1(a) while Art. 60.12 enforced Rec. 60C.1. The relevant material from those two Recommendations has now been incorporated into the rules, as Art. 60.8 on terminations and Art. 60.10 on compounding forms.

The new Art. 60.6 may seem superficially similar to Art. 60.5 but, whereas Art. 60.5 concerns use of the letters u, v or i, j used interchangeably or in any other way incompatible with modern typographical practices, Art. 60.6 concerns their use in any way incompatible with modern nomenclatural practices (hence japonicus, not ‘iaponicus’), and additionally contains rules on transcription of the Greek diphthong ευ as eu not ev (hence Euonymus, not ‘Evonymus’).

Art. 60.12 is also new and rules that a hyphen in the name of a fossil-genus is always treated as an error to be corrected by deletion of the hyphen. In non-fossil generic names, a hyphen present in the protologue must be maintained and can only be removed through conservation.

Finally, the former App. I, on the names of hybrids, is no longer an Appendix but part of the main body of the Code, following a proposal accepted in Shenzhen. The previous numbering of its Articles (Art. H.1–H.12) has been maintained, and it forms Chapter H (the “H” standing for hybrids), immediately following Chapter F and immediately preceding Division III.

Bibliographic references in the Examples

The Editorial Committee was concerned about inconsistency in the Examples, whereby names were followed, in parentheses, by either the year of publication or the full bibliographic reference. There had been a rationale for this difference in citation: names that could be found in nomenclatural indices (e.g. the International Plant Names Index [IPNI]) were cited with the year only, whereas names more difficult to find, such as names of infraspecific taxa published prior to 1976 or names of fossil-taxa, were provided with a full reference. However, sometimes full references were provided when names could readily be found in indices, partly as a result of those indices having been developed since the Examples entered the Code (e.g. Index Fungorum, MycoBank, and Index Nominum Algarum) and, conversely, sometimes only the year was cited when the full reference would not be easy to find. Rather than delete references already provided, the Editorial Committee decided that whenever a date was cited it should be expanded to a full reference, thus making the Code more self-contained. Sandra Knapp is especially thanked for completing the arduous task of looking up and inserting most of these references, which were then reviewed by the Rapporteur-général.

The Glossary

The Glossary has retained its basic structure but has been revised and updated. New entries in the Glossary include: “affirmation”, “attributed”, “identifier”, “nomenclatural act”, “pro synonymo”, “protected name”, and “superseded”, while some existing entries have been substantially revised, e.g. “autonym”, “holotype”, and “rank”; the entry for “alternative family name” has been changed to “nomen alternativum” to accord with the preferred term in the Code. This reflects the fundamental role of the Glossary, which is strictly to explain terms used in the Code, and where possible to do so using the precise wording associated with these terms in the Code. The Glossary does not seek to cover all terms useful in the nomenclature of algae, fungi, and plants; for that, users can refer to a work such as Hawksworth, Terms used in Bionomenclature (2010; online at

The Appendices

The Appendices of the Code (excluding the former App. I, now Chapter H, on names of hybrids) have been maintained over the last several years by John Wiersema as an online database currently hosted by the Department of Botany at the Smithsonian National Museum of Natural History in Washington, DC ( They will continue to be available online in this form, while the possibility of publication as printed matter or in Portable Document Format (PDF) is not precluded.

When the former App. I (names of hybrids) became Chapter H, the remaining Appendices required re-numbering. The Editorial Committee decided that the former App. VI (suppressed works), could logically become the new App. I, because its impact can affect names at all ranks. App. II–V therefore remain unchanged, and the former App. VII and VIII (binding decisions), which were relatively new to the Code, become App. VI and VII, respectively. The lists of protected names of fungi (Art. F.2) approved in Shenzhen are incorporated as individual names, indicated as protected, in App. IIA, III, and IV according to their rank. No lists of rejected names of fungi (Art. F.7) have yet been approved.

Formatting and standards used in the Code

Recent editions of the Code have used three different sizes of type, with the Recommendations and Notes set in smaller type than the Articles, and the Examples and footnotes in smaller type than the Recommendations and Notes. These type sizes, which have been maintained in this edition, reflect the distinction between mandatory rules (Articles), complementary information or advice (Notes and Recommendations), and explanatory material (Examples and footnotes). Notes, which explain something that may not at first be readily apparent but is covered explicitly or implicitly elsewhere in the Code, are appropriately identified (at least in the print edition of the Code) with an “i” for “information”, highlighted in the same way as the Article numbers. Notes have binding effect but, unlike Articles, do not introduce any new provision or concept. Examples are distinguished, in addition to the smaller font size, by being indented. There are 19 Examples that illustrate particular, lettered clauses of Articles (Art. 9.19, 10.7, 36.1, 41.8, and 54.1), in which case the respective letter is cited in parentheses at the beginning of the Example, e.g. “(a)”.

As in all recent editions, scientific names under the jurisdiction of the Code, irrespective of rank, are consistently printed in italic type. The Code sets no binding standard in this respect, as typography is a matter of editorial style and tradition, not of nomenclature. Nevertheless, editors and authors, in the interest of international uniformity, may wish to consider following the practice exemplified by the Code, which has been well received in general and is followed in a number of botanical and mycological journals. To set off scientific names even better, italics are not used for technical terms and other words in Latin, although they are still used for word elements that are part of a scientific name.

The Editorial Committee has tried hard to achieve uniformity in bibliographic style and formal presentation. Author citations of scientific names appearing in the Code are standardized in conformity with Brummitt & Powell, Authors of plant names (1992), updated as necessary from the International Plant Names Index (, albeit with additional spacing, as mentioned in Rec. 46A Note 1. The titles of books in bibliographic citations are abbreviated in conformity with Taxonomic literature, ed. 2 (TL-2; Stafleu & Cowan in Regnum Veg. 94, 98, 105, 110, 112, 115, 116. 1976–1988; Supplements 1–6 by Stafleu & Mennega in Regnum Veg. 125, 130, 132, 134, 135, 137. 1992–2000; Supplements 7 & 8 by Dorr & Nicolson in Regnum Veg. 149, 150. 2008 & 2009; online at or, when not in TL-2, by analogy, but always with capital initial letters. For journal titles, the abbreviations follow Bridson & al., BPH-2. Periodicals with botanical content. Constituting a second edition of Botanico-periodicum-huntianum (2004; online at or, when not in BPH-2, by analogy. Standard herbarium codes follow Thiers, Index herbariorum (continuously updated; online at


We first thank our fellow members of the Editorial Committee for their hard work, patience, helpfulness, and friendship, and acknowledge the support for their work on nomenclature by their respective institutions.

We are grateful to the following for their contributions at the Nomenclature Section: De-Yuan Hong for an inspiring opening speech at the Section; the Recorders, Li Zhang and Yun-Fei Deng; the Recorders’ Assistant, Anna Monro; the Vice-presidents, Renée Fortunato, Werner Greuter, De-Zhu Li, John McNeill, Gideon Smith, and Karen Wilson; the members of the Nominating Committee, Alina Freire-Fierro, Vicki Funk, Dmitry Geltman, David Hawksworth, Regina Hirai, Jin-Shuang Ma, David Middleton, Gideon Smith, and Kevin Thiele; the Tellers, Heather Lindon, Melanie Schori, Gustavo Shimizu, and Yi-Hua Tong; and of course the Organizing Committee of the IBC and all the local staff and volunteers in Shenzhen who helped the Section run smoothly.

The Council and officers of the IAPT, including its successive Presidents, Vicki Funk and Patrick Herendeen, and Secretary-General, Karol Marhold, are thanked for maintaining the IAPT’s traditional commitment to nomenclature by funding the Editorial Committee meeting in Berlin. Eva Senková, the Managing Secretary at the IAPT central office in Bratislava, is especially thanked for her help with the preliminary guiding vote, institutional votes, and travel logistics and expenses for the IBC and Editorial Committee meeting. Matúš Kempa, also at the IAPT central office, provided IT support for the preliminary guiding vote.

Thomas Borsch, Director of the Botanischer Garten und Botanisches Museum Berlin (BGBM), Freie Universität Berlin, is thanked for hosting the Editorial Committee meeting, providing a conference room, library facilities, and internet access. We are also grateful to Gabriela Michaelis, in the Directorate at BGBM, for valuable help with the logistics of the meeting. The staff of the BGBM Library are also thanked for providing publications that were not available online. The staff of the Library of the Natural History Museum, London, helped Sandra Knapp with access to various publications during her task of adding bibliographic references to the Examples of the Code.

We thank Paul van Rijckevorsel for editorial suggestions and especially for creating such a helpful resource in his “Overview of the Codes since 1867”, hosted on the IAPT website ( This has been invaluable in tracing provisions of the Code back in time to clarify meanings that were not immediately obvious.

We also gratefully acknowledge others who have provided editorial suggestions, ideas, or Examples: Robert Andersen, John David, Vincent Demoulin, Yun-Fei Deng, Kanchi Gandhi, Mark Garland, Rafaël Govaerts, Martin Head, Paul Kirk, Joseph Kirkbride, David Mabberley, Gregory Mueller, Luis Parra, Richard Rabeler, Rosa Rankin, Alexander Sennikov, Judith Skog, Mark Watson, Karen Wilson, Peter Wilson, William Woelkerling, Xiang-Yun Zhu, and Gea Zijlstra.

Franz Stadler, the Production Editor of Regnum Vegetabile, is thanked for his excellent editing, formatting, and page layout of the final draft of the Shenzhen Code. The cover design was skilfully drawn by Pollyanna von Knorring. The photograph of the Nomenclature Section was taken and provided by Li Zhang, Recorder. Sven and Per Koeltz, of Koeltz Botanical Books, are thanked for publishing the Shenzhen Code and permitting its online publication by the IAPT.

The Rapporteur-général thanks his wife, Christine Turland, for remaining so tolerant and understanding during the time he devoted to this edition of the Code.

The implementation of the Code between Congresses depends continuously on the effort invested by members of the Permanent Nomenclature Committees, altogether some 130 individuals, who work principally on proposals for conservation, protection, or rejection of names, suppression of works, and requests for binding decisions. There are also the members of the Special-purpose Committees established by an IBC with a mandate to investigate particular nomenclatural problems and to report with solutions to the next IBC. Augmenting these efforts with considerable input of time and expertise are the relevant column editors of the journals Taxon and IMA Fungus, where the proposals, requests for decisions, and committee reports are published. The nomenclature of algae, fungi, and plants is remarkable for being supported by a vast amount of meticulous and effective work undertaken voluntarily by so many taxonomists. All users of this Code benefit from these efforts, and we are sincerely grateful to all who participate in this work.

The online version of the main text of the Code and the online database of its Appendices are dependent on the continued support of the two institutions that host the websites: the central office of the IAPT (Bratislava), for the main text, and the Department of Botany at the Smithsonian National Museum of Natural History (Washington, DC) for the Appendices.

The International Code of Nomenclature for algae, fungi, and plants is published under the authority of the International Botanical Congress (IBC), while its Chapter F, on names of organisms treated as fungi, is published under the authority of the International Mycological Congress (IMC). Provisions for the amendment of the Code are detailed in Division III. The next IMC, IMC11, will take place in San Juan, Puerto Rico from 16–21 July 2018, with its Nomenclature Session on 19 July. IMC12 will take place in 2022. The next IBC, the XX IBC, will take place in Rio de Janeiro, Brazil from 23–29 July 2023, with its Nomenclature Section meeting during the preceding week (17–21 July). Proposals to amend this Code (excluding Chapter F) may be published in Taxon starting in 2020 and ending in 2022. In late 2019 or early 2020 a notice will appear in Taxon announcing the opening of the Proposals column and providing instructions on procedure and format. Proposals to amend Chapter F, to be considered at IMC12 in 2022, may be published in IMA Fungus, in which a similar notice will appear.

This Code, as with previous editions, is the culmination of a multi-year process of international cooperation and collaboration. Its scientific standing is dependent on the voluntary acceptance of its rules by authors, editors, publishers, and other users of the names of algae, fungi, and plants. We trust that you, as one of these users, will be happy to accept this Shenzhen Code.

Berlin and Beltsville, 24 May 2018

Nicholas J. Turland John H. Wiersema