TAXON 53 (1) • February 2004: 159-161 Barkley & al. • A review of the ICBN

A review of the International Code of Botanical Nomenclature with respect to its compatibility with phylogenetic classification

Theodore M. Barkley1, Paula DePriest2, Vicki Funk2, Robert W. Kiger3, W. John Kress3, John McNeill4, Gerry Moore5, Dan H. Nicolson2, Dennis W. Stevenson6 & Quentin D. Wheeler7 [note: order of authors determined alphabetically]

1 Botanical Research Institute of Texas, 509 Pecan Street, Fort Worth, Texas 76102, U.S.A. barkley® brit.org 2 Botany, MRC-166, United States National Herbarium, National Museum of Natural History, Smithsonian Institution, P.O. Box 37012, Washington D.C. 20013, U.S.A. [email protected]; funk.vicki@ nmnh.si.edu; [email protected]; [email protected] 3 Hunt Institute for Botanical Documentation, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, U.S.A. [email protected] 4Royal Botanic Garden, Edinburgh, EH3 SLR, Scotland, U.K. [email protected] 5Brooklyn Botanic Garden, 1000 Washington Avenue, Brooklyn, New York 11225, U.S.A. gerrymoore@bbg. org (author for correspondence) 6 The New York Botanical Garden, Bronx, New York 10458 U.S.A. [email protected] 7Division of Environmental Biology, National Science Foundation, 4201 Wilson Boulevard, Arlington, Virginia 22230, U.S.A. [email protected]

This article presents a summary of a discussion on believe that this assertion is the case, but many others do the current Code of botanical nomenclature (Greuter & not. al., 2000) that took place at the Linnaean Nomenclature Discussion: From a nomenclatural perspective, the Workshop held on 26-28 June 2002 at the Hunt Institute rank of species is indeed basic. The species is the only for Botanical Documentation in Pittsburgh, Pennsylvania primary rank whose names must be typified by particular (see also Barkley & al., 2004). An article by article vet- specimens (or illustrations) (Art. 8.1). Thus, the names of ting of the Code was conducted with the goal of identi- species are typified (anchored) by concrete entities. fying parts of it that may be in conflict with phylogenet- Types of names of families are the same as those of the ic approaches to classification. It was concluded that the generic names on which they are based (Art. 10.6) and Code does not contain any rules that actually prevent types of generic names are the types of names of species phylogenetic classification. However, it was noted that (but see Art. 10.4 for rare exceptions where a specimen some articles could benefit from clarification. Each arti- may typify a generic name). Thus, the typification "cas- cle that was identified during the workshop as being cade" ends with the type of the species. Another way to potentially problematic is discussed below. In some cases look at the species rank being basic from a nomenclatur- it was determined that the language of the current Code al perspective is that one cannot describe a family name should be modified and formal proposals for such without identifying at least one generic name (the type) changes are being published separately (Moore & al., that is included within it, nor can one describe a new 2004). For each case, if a similar concern could be raised genus without citing at least one species (the type) that is with the language in the International Code of included within it (again see Art. 10.4 for exception); Zoological Nomenclature (Ride & al., 1999) this was however, one can describe a species without citing the also identified. names of any infraspecific taxa. Proposed changes: None. Article 2.1: "Every individual plant is treated as Is there a similar issue with the ICZN? No. The belonging to an indefinite number of taxa of consecu- ICZN does not identify the species as "basic". tively subordinate rank, among which the rank of species (species) is basic". Article 3.1: "The principal ranks of taxa in Concern: The main concern with this article is the descending sequence are: kingdom (regnum), division designation of the species rank as being "basic". It was or phylum (divisio, phylum), class (classis), order suggested that this may lead some practitioners to con- (ordo), family (familia), genus (genus), and species clude that the Code states that those taxa assigned the (species). Thus, each species is assignable to a genus, rank of species are somehow more "real" than taxa each genus to a family, etc". assigned to other ranks. Indeed some taxonomists do Concern: The second sentence of this article (also

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Article 2.1: "every individual plant is treated as belong- clear that names of taxa are typified and not the taxa ing to an indefinite number of taxa...") may lead some to themselves. conclude that each genus must be assignable to a family Proposed changes: None. (and thus each family must be assignable to an order Is there a similar issue with the ICZN? Yes. The etc.). Therefore, it might be concluded that the Code ICZN also does not explain how typification keeps forces one to provide a complete classification for an nomenclature distinct from taxonomy. organism. This is problematic because information for a taxon may be insufficient to provide a complete classifi- Articles 16, 17: Names of taxa above the rank of cation of it. family. Discussion: Article 3.1 (and 2.1) is referring to Concern: The Code treats names above the rank of hypothetical scenarios and is not placing any require- family very differently from the way it treats those names ments on how extensively a worker must classify a given at the rank of family and below. Some may regard the taxon. How many ranks a taxonomist uses is up to Code as inconsistent since it requires typification and her/him. However, names of species and infrageneric priority at the rank of family and below, but does not taxa (binomials) must include a genus name (Art. 21.1, require these above the rank of family. 23.1), although the generic placement of such taxa can Discussion: The current wording arises from taxon- change. The same applies for infraspecific names (Art. omists having come to grips with the fact that a one-size- 24.1). fits-all approach does not work with regard to nomencla- Proposed changes: Add a note to the Code with ture at different ranks. Above the rank of family, the examples that show this (see Moore & al., 2004). Code leaves things largely unregulated (no typification Is there a similar issue with the ICZN? No. The requirements, priority does not apply). The reasoning ICZN does not have an article that specifies ranks and here is that the number of names being used at these their proper relative order. ranks is small and that common usage may indeed work very well. However, at the rank of family and below the Articles 3-5: These articles introduce rank-denot- number of names available is significantly higher. ing terms and their relative order. Therefore, more stringent rules are needed for these Concern: The articles that introduce rank-denoting ranks including a separate article (Art. 11.1) requiring terms and their proper relative order do not clearly state that each taxon with a particular circumscription, posi- that two taxa assigned the same taxonomic rank are not tion, and rank can bear only one correct name. Above the necessarily comparable in any way. For example, two rank of family, less appears to be better because the goal genera in the Compositae (Asteraceae) are not necessar- of Art. 11.1 seems to be largely achieved to a great extent ily similar with regard to their times of origin. without regulation; at the rank of family and below more Discussion: These articles simply specify the set of regulation (rules, committees) is needed. rank-denoting terms that may be used and their proper Proposed changes: None. relative order. The Code in no way states or implies that Is there a similar issue with the ICZN? Yes. The taxa at a given rank are or should be comparable in any ICZN does not regulate names in any way above the rank way. of superfamily. Proposed changes: None. Is there a similar issue with the ICZN? No and Art 16.1 (b): "descriptive names, not so formed, yes. No, the ICZN does not have an article that specifies which apply to taxa with a recognized circumscrip- rank-denoting terms and their proper relative order. Yes, tion and which may be unchanged at different the ICZN also does not clearly state that taxa of a given ranks". rank are not necessarily comparable in any way. Concern: This article allows untypified suprafamil- ial names (e.g., Angiospermae) to be used unchanged at Article 7-10: Articles governing typification. different ranks. The Code could be viewed as inconsis- Concern: These articles do not clearly state that typ- tent since it provides either recommended or mandatory ification is merely the mechanism by which nomencla- endings for typified suprafamilial names. Also the valu- ture is kept distinct from classification. able set inclusivity/exclusivity information is lost when Discussion: Names are assigned types, whereas taxa names at a given rank are not of the same form (or names are assigned circumscriptions and descriptions. A taxon's of different ranks are of the same form). circumscription (or description) is subject to change, Discussion: There is a long history in botanical whereas a name's type cannot change without formal nomenclature (perhaps now waning) of using character- conservation. These articles simply lay out the rules for based names for suprafamilial taxa in which all repre- how names are to be typified. These articles do make it sentatives possess the character (e.g., Sympetalae). If the

160 TAXON 53 (1) • February 2004: 159-161 Barkley & al. • A review of the ICBN

use of such names is declining, is it necessary to do any- the recognition of non-monophyletic groups. For exam- thing? Perhaps they might die a natural death like initial ple, Taxonomist 1 works in the genus Alpha (comprising capitalization of some specific epithets (it is permitted species a-z) and revises a subgenus (that does not but almost no one does so). Previously, it has been pro- include the type of the genus name). Taxonomist 1 gives posed that untypified descriptive names be banned. the subgenus the name Alpha subg. Beta. This act auto- Priority does not apply above the rank of family, so no matically establishes the autonym Alpha subg. Alpha. one is forced to use a descriptive name. Taxonomist 1 circumscribes A. subg. Beta to include Is there a similar issue with the ICZN? Yes. species a-f. Hasn't Taxonomist l's action thereby result- Names above superfamily are not regulated and can be ed in a circumscription of Alpha subg. Alpha that formed in any manner. includes all species not included in A. subg. Beta (i.e., species g-z), regardless of the monophyly of that group? Articles 21-23: Names of subdivisions of genera, Discussion: While the autonym Alpha subg. Alpha species. was automatically established with the publication of Concern: The binominal construction of these Alpha subg. Beta, its circumscription was never estab- names forces one to assign a taxon in these ranks to a lished (so "no" to the question posed above). Taxonomist genus even if such placement may be uncertain. Thus, if 1 may have circumscribed Alpha subg. Beta to include the generic placement of a subgenus or a species species a-f, but this act (which established the name changes, its name must be changed. This is different Alpha subg. Alpha) does not mean that Taxonomist 1 has from the situation in those ranks where taxa are assigned indirectly circumscribed the taxon represented by the uninomials. For example if a tribe is shifted from one autonym to include species g-z. The autonym rules auto- family to another the name of the tribe is not changed. matically establish names (autonyms only); they do not Discussion: Using binominal nomenclature is a automatically establish taxa or their circumscriptions. common practice when communicating about a group in Proposed changes: Add notes under Articles 22 and which there are multiple kinds. It greatly assists in pre- 26 to make it clearer that names and not taxa are estab- venting homonymy in a nomenclatural system. lished (Moore & al, 2004). Binominal nomenclature is not limited to scientific Is there a similar issue with the ICZN? Yes. The nomenclature; for example, common names of species ICZN does not have articles discussing the automatic are often binominal (e.g., snowy owl, Eraser fir). The establishment of autonyms, but the provisions for binomial does force one to assign a species to a genus "nominotypical taxa" (see Art. 44) appear to have the and thus a change in generic placement will require a same effect. change in name. However, this can also be quite useful in communication. For example, if the taxon Malus hypo- theticus were later found actually not to be an apple but an orange and hence a member of the taxon Citrus, the LITERATURE CITED name would change to Citrus hypotheticus (assuming Barkley, T. M, DePriest, P., Funk, V, Kiger, R. W., Kress, this epithet were available). This change is actually use- W. J. & Moore, G. 2004. Linnaean nomenclature in the 21 century: a report from a workshop on integrating tra- ful in that it updates the taxonomic address of the plant, ditional nomenclature and phylogenetic classification. and it is a perfectly logical manoeuvre when communi- Taxon53: 153-158. cating with binomials. Indeed it would be inconvenient Greuter, W., McNeill, J, Barrie, F. R, Burdet, H. M, and illogical to continue to refer the taxon as Malus Demoulin, V., Filgueiras, T. S, Nicolson, D. H, Silva, P. hypotheticus once it were shown that it did not belong to C, Skog, J. E., Trehane, P., Turland, N. J. & the taxon Malus (but rather Citrus). Hawksworth, D. L. (eds.). 2000. International Code of Proposed changes: None. Botanical Nomenclature (Saint Louis Code). Adopted by the Sixteenth International Botanical Congress St. Louis, Is there a similar issue with ICZN? In the ICZN Missouri, July-August 1999. Koeltz, Konigstein. [Regnum only the names of species are binomials (and not those of t&g. 138.] taxa at infrageneric ranks such as subgenus). Moore, G, Barkley, T. M, DePriest, P., Funk, V, Kiger, R. W., Kress, W. J, Nicolson, D. H, Stevenson, D. Wm. & Articles 22, 26: Autonym articles Wheeler, Q. D. 2004. (065-067) Proposals to amend Concern: The autonym rules state that the first Article 3.1, Article 22.3, and Article 26.3. Taxon 53: 214. instance of valid publication of a name of a subdivision Ride, W. D. L, Cogger, H. G, Dupuis, C, Kraus, O., Minelli, A, Thompson, F. C. & Tubbs, P. 1999. of a genus or of an infraspecific taxon under a legitimate International Code of Zoological Nomenclature. name of a genus or a species, respectively, automatically International Commission on Zoological Nomenclature, establishes the corresponding autonym (Arts. 22.3, 26.3). London. Some practitioners are concerned that this rule may force

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