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The PhyloCode
Chapter X. Species Names
Article 21.
21.1. This code does not govern the establishment or precedence of species names. To be considered available (ICZN) or validly published (ICBN, ICNB), a species name must satisfy the provisions of the appropriate rank-based code (e.g., ICNB, ICBN, ICZN). This article describes how species names governed by the rank-based codes are to be interpreted and used under this code.
Note 21.1.1. Article 21 applies to all species names, including replacement names (deliberate substitutes of the ICNB, avowed substitutes of the ICBN, new replacement names of the ICZN).
21.2. The name of a species under the rank-based codes (except the ICVCN) is a binomen (two part name), the first part of which is a generic name (i.e., a name that is tied to the rank of genus) and the second part of which is a specific name (ICZN) or epithet (ICNB, ICBN) (i.e., a name that is tied to the rank of species). Because this code is independent of categorical ranks (Art. 3.1), the first part of a species binomen is not interpreted as a genus name but instead as simply the first part of the species name (a prenomen; see Art. 21.4), and the second part of a species binomen is associated with the species as a kind of biological entity, not as a rank (Note 3.1.1).
21.3. This code also does not govern the establishment of names associated with ranks below that of species under the rank-based codes ("infraspecific names"); however, such names may be used in conjunction with phylogenetic nomenclature. Because this code is independent of categorical ranks (Art. 3.1), the third (and subsequent) part(s) of an infraspecific name is (are) associated with the species as a biological entity rather than with the subspecific (and varietal) rank of traditional nomenclature. Thus, infraspecific names may be used to refer to incompletely separated species, but their use to refer to patterns of variation that do not reflect even partial species (lineage) separation (e.g., polymorphism, ecophenotypic variation, and some examples of local adaptation and geographic variation in conspicuous characters) is discouraged.
21.4. A prenomen is the first part of a species binomen. A prenomen has no necessary tie to any categorical rank under this code. However, to satisfy the requirements of the rank-based codes, a prenomen must be used (and implicitly or explicitly associated with the rank of genus) when establishing a new species name, even though it may not have been established as a clade name under this code.
Recommendation 21.4A. When establishing a new species name (binomen) under the appropriate rank-based code, some mechanism should be used to indicate whether the generic name (prenomen) is an established clade name under this code. If symbols are used, their meaning should be made clear.
Example 1. ©Hypotheticus could indicate that the prenomen Hypotheticus is an established clade name, while Hypotheticus (with no symbol) could indicate that this prenomen has not been established as a clade name under this code. If so, the meaning of the symbol © should be clearly indicated.
Example 2. Hypotheticus (with no symbol) could indicate that this prenomen has been established as a clade name under this code, while [R]Hypotheticus could indicate that the prenomen Hypotheticus is not an established clade name ("R" meaning governed by a rank-based code). If so, the meaning of the symbol [R] should be clearly indicated.
Note 21.4A.1 Although Examples 1 and 2 each use only one symbol, it may be clearer to use symbols to indicate both situations. Using absence of a symbol to designate nomenclatural status is potentially confusing because its absence may simply result from accidental omission of the symbol. Furthermore, some readers may misinterpret absence of a symbol because they are unaware of the author's convention.
Note 21.4A.2 If a symbol (e.g., quotation marks) is used to indicate non-monophyly of the taxon designated by the prenomen, it is not necessary to indicate that the prenomen is not an established clade name under this code.
Note 21.4A.3 If a symbol is used to indicate non-monophyly or questionable monophyly of the taxon designated by the prenomen, this does not imply that the author does not accept the species. Therefore, the species name should not be interpreted as not validly published under ICBN (2006) Art. 34.1.
Recommendation 21.4B. When publishing the name of a new species, selection of a generic name (prenomen) will require consideration of the nomenclatural consequences under both the appropriate rank-based code and this code. In general, a generic name (ICNB, ICBN) or genus-group name (ICZN) that is also an established clade name (or is simultaneously being established as a clade name) under this code should be selected if possible. (If the names of more than one clade in a nested series of clades satisfy these conditions, any one of the names may be selected.) If this is not possible, an existing generic (or genus-group) name may be used, even if the monophyly of the associated taxon under the rank-based code is unknown or doubtful, or a new generic name (prenomen) may be used. If the species to be named cannot be assigned to any taxon with which a generic (or genus-group) name has been associated under the appropriate rank-based code, then the only option is to publish a new name to serve as a generic name under the appropriate rank-based code (a prenomen under this code). This name may be simultaneously established as a clade name under this code.
Example 1. If a new species is to be given the binomen Sorex hockingensis, and the name Sorex has already been established both as a clade name under this code and as the name of a genus under the ICZN, then the binomen should appear as Sorex hockingensis, new species (or an equivalent expression such as n. sp.), with or without a symbol (e.g., ©) indicating that Sorex is an established clade name (see Rec. 21.4A, Examples 1 and 2).
Example 2. If the taxon associated with the genus name Sorex in Example 1 is thought to be monophyletic but has not previously been established as a clade name, the clade name Sorex could be established simultaneously with the publication of the binomen Sorex hockingensis.
Example 3. If the only preexisting genus to which a new species (for which the epithet vulgaris is selected) can be assigned (Hypotheticus) is thought to be non-monophyletic or its monophyly has not been investigated, and the species is part of a clade (Cladius) that could be named as a genus under the appropriate rank-based code, then the binomen could appear as Cladius vulgaris, new genus and species (or an equivalent expression), with or without a symbol (e.g., ©) indicating that Cladius is an established clade name (see Rec. 21.4A, Examples 1 and 2). If this is done, Cladius should be validly published (ICNB, ICBN) or made available (ICZN) simultaneously as a genus name under the appropriate rank-based code, and it should also be established as a clade name under this code if it has not previously been established. Alternatively, if it were considered premature to establish the name Cladius, the binomen could appear as Hypotheticus vulgaris, new species (or an equivalent expression), with or without a symbol (e.g., [R]) indicating that Hypotheticus is not an established clade name (see Rec. 21.4A, Examples 1 and 2) or a symbol (e.g., quotation marks) indicating that Hypotheticus is not monophyletic (see Note 21.4A.2).
Example 4. In the situation described in Example 3, if there is not sufficient evidence that the new species is part of any clade that could be named as a genus under the appropriate rank-based code, then the binomen could appear as Hypotheticus vulgaris, new species (or an equivalent expression), with or without a symbol (e.g., [R]) indicating that Hypotheticus is not an established clade name (see Rec. 21.4A, Examples 1 and 2) or a symbol (e.g., quotation marks) indicating that Hypotheticus is not monophyletic (see Note 21.4A.2). Alternatively, a new generic name (prenomen) could be published in combination with the new specific name or epithet under the rank-based code.
Example 5. If a new species, to be named campestris, cannot be assigned to any taxon (whether monophyletic or not) with which a generic name (ICNB, ICBN) or genus-group name (ICZN) has been associated under the appropriate rank-based code, it would be necessary to publish a new generic name (e.g., Imaginarius) in combination with the new specific name or epithet under the rank-based code. If Imaginarius is simultaneously established under this code as a clade name, then the binomen should appear as Imaginarius campestris, new genus and species (or an equivalent expression), with or without a symbol (e.g., ©) indicating that Imaginarius is an established clade name (see Rec. 21.4A, Examples 1 and 2).
Example 6. If, in the previous example, the name Imaginarius is not simultaneously established as a clade name under this code, then the binomen should appear as Imaginarius campestris, new genus and species (or an equivalent expression), with or without a symbol (e.g., [R]) indicating that Imaginarius is not an established clade name (see Rec. 21.4A, Examples 1 and 2).
Recommendation 21.4C. When establishing a new species name under the appropriate rank-based code, the protologue should include a description of the evidence indicating that the named species represents a separately evolving lineage from other named species, or an unambiguous bibliographic citation (Art. 9.9) to a previous publication containing this information.
Note 21.4C.1. The evidence indicating that the named species represents a separately evolving lineage from other named species may take various forms, including (but not restricted to) those commonly adopted as species criteria (e.g., absence of interbreeding and/or gene flow, reciprocal monophyly, a unique combination of character states).
Note 21.4C.2. The provision of the evidence used to infer that the species represents a separately evolving lineage does not imply that subsequent users of the name must rely on the same evidence or adopt the same species criteria.
21.5. Subsequent to a species binomen becoming available (ICZN) or validly published (ICBN, ICNB) under the appropriate rank-based code, the second part of the species binomen may be treated as the name of the species (i.e., a species uninomen) under this code. In this context, the species uninomen may be combined with the names of clades other than the prenomen (see Rec. 21A).
Recommendation 21.5A. When the prenomen is used subsequent to the species binomen becoming available (ICZN) or validly published (ICBN, ICNB), some mechanism should be used to indicate whether the generic name (prenomen) is an established clade name under this code (see examples under Rec. 21.4A).
Recommendation 21.5B. When the second part of a species binomen is treated as the name of a species subsequent to the species binomen becoming available (ICZN) or validly published (ICBN, ICNB), it should be accompanied by one or both of the following:(a) the prenomen; (b) the author(s) and year of the publication in which the epithet (ICNB, ICBN) or specific name (ICZN) was validly published (ICNB, ICBN) or made available (ICZN).
Note 21.5B.1. Under the ICBN, the author(s) of the binomen is (are) commonly cited but the year is commonly not cited. In contrast, both the author and year are commonly cited under the ICZN. Under this code, if the prenomen is not used in combination with the specific name or epithet, both the author and year of the specific name or epithet should be cited. If the prenomen is used, citation of the author and year are optional.
Example 1. The species that is referred to as Vultur gryphus or Vultur gryphus Linnaeus under the ICZN may be referred to under this code as Vultur gryphus or Vultur gryphus Linnaeus or gryphus Linnaeus 1758. Any of these forms of the species name may be associated with additional clade names to indicate hierarchical relationships (see Rec. 21A); for example, Aves/Vultur/gryphus Linnaeus 1758 or Aves/Vultur gryphus Linnaeus.
Recommendation 21A. When species names are used in the context of this code, it will often be useful to associate them with one or more prenomina as well as the names of more inclusive clades. Hierarchical relationships among the taxa designated by those names can be indicated in a variety of ways, but the taxa should be listed in order of decreasing inclusiveness from left to right. In addition, symbols such as those in the examples under Rec. 21.4A may be used not only with prenomina but also with names associated with groups above and below the rank of genus under the rank-based codes (but for simplicity, such symbols are not included in the following examples).
Example 1. The species originally named Anolis auratus Daudin 1802 has been placed in at least two different genera, named Anolis and Norops. If those names were to be established under this code as the names of (nested) clades, the name and relationships of the species could be indicated in any of the following ways (not an exhaustive list): Anolis/auratus Daudin 1802, or Norops: auratus Daudin 1802, or Anolis/Norops/auratus Daudin 1802, or Anolis Norops auratus Daudin 1802. For optional use of parentheses to indicate that a specific name or epithet was originally combined with a different generic name, see Note 21A.3.
Example 2. If the name of a species under the ICZN is Diaulula sandiegensis (Cooper 1863), and if Diaulula has not been established as a clade name under this code (for example, because there is presently insufficient data to establish monophyly), and if the name Discodorididae has been established as the name of a more inclusive clade under this code, then the name and relationships of the species could be indicated in any of the following ways (not an exhaustive list): Diaulula sandiegensis Cooper 1863, or Discodorididae Diaulula sandiegensis Cooper 1863, or Discodorididae/sandiegensis Cooper 1863, or Discodorididae sandiegensis Cooper 1863. For optional use of parentheses to indicate that a specific name or epithet was originally combined with a different generic name, see Note 21A.3.
Note 21A.1. When a species uninomen is combined with other names than the prenomen, the names do not have to agree in gender and number (plural vs. singular). Therefore, the ending of the uninomen does not have to change. The uninomen can be viewed as a name in its own right, rather than as an adjectival modifier of the clade name.
Note 21A.2. By combining the second part of a species binomen with the name of a clade that is not a genus under the appropriate rank-based code (see variants that do not use the name Diaulula in Rec. 21A, Example 2), it is possible to provide phylogenetic information for a species without using a generic name (ICNB, ICBN) or genus-group name (ICZN) that has not been established as a clade name under this code.
Note 21A.3. If a specific name (ICZN) or epithet (ICNB, ICBN) is associated with just one prenomen, so the combination resembles a binomen, parentheses enclosing the name of the author and year of publication of the specific name (ICZN) or the author of the epithet (ICNB, ICBN) may be used to indicate that the specific name or epithet was originally combined with a different generic name, following the conventions of the appropriate rank-based code (which differ in whether the year is commonly cited and whether the author of the accepted combination should also be cited). The use of parentheses for this purpose is optional, which is consistent with the decreased emphasis on taxonomic ranks under this code. Parentheses may also be used if a specific name (ICZN) or epithet (ICNB, ICZN) is associated with just one clade name of supra-generic rank under the rank-based codes.
Example 1. In the name Norops auratus (Daudin 1802), the use of parentheses indicates that Daudin originally published (made available; ICZN) the specific name auratus in combination with a different generic name. Use of parentheses in this case is optional (e.g., see the citation of this same name and author without parentheses in Rec. 21A, Example 1).
Example 2. In the name Physostegia/virginiana (Linnaeus) Bentham, the use of parentheses indicates that Linnaeus originally published the specific epithet virginiana in combination with a different generic name and that Bentham first validly published (ICBN) the binomen Physostegia virginiana.
Example 3. In the name Discodorididae sandiegensis (Cooper 1863) (see Rec. 21A, Example 2), the use of parentheses indicates that Cooper originally published the specific name sandiegensis in combination with a different taxon name.