21.1
This code does not govern the establishment or precedence of species names or names associated with ranks below species under the rank-based codes (e.g., ICNP, ICNAFP, ICZN). To be considered available (ICZN) or validly published (ICNAFP, ICNP), the name of a species or infraspecific taxon must satisfy the provisions of the appropriate rank-based code. This article contains recommendations about how to publish or use previously published names of species and infraspecific taxa governed by rank-based codes in conjunction with clade names governed by this code.
Note 21.1.1
In Article 21.1, the term “names of species and infraspecific taxa” does not refer to names established under this code that apply to clades that correspond in composition to or are nested within taxa that are ranked as species under a rank-based code.
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 (ICNP, ICNAFP) (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 simply as the name of a taxon that includes that species.
21.3
To satisfy the requirements of the rank-based codes (see Art. 21.2), a specific or infraspecific name (ICZN) or epithet (ICNAFP) must be published in unambiguous combination with a name that is implicitly or explicitly associated with the rank of genus (even though it may not have been established as a clade name under this code). For names governed by the ICZN, this practice must be followed throughout the publication that establishes the name (ICZN Art. 11.4).
Recommendation 21.3A
When establishing a new species name (binomen) under the appropriate rank-based code, some mechanism should be used to indicate whether the genus name is an established clade name under this code. If symbols are used, their meaning should be made clear.
Example 1
[P]Hypotheticus could indicate that Hypotheticus is an established clade name, while [nP]Hypotheticus could indicate that Hypotheticus has not been established as a clade name under this code (“n” meaning “not”). If so, the meanings of the symbols [P] and [nP] should be clearly indicated.
Note 21.3A.1
Although Example 1 uses one symbol to indicate establishment under this code and another symbol to indicate the absence of such establishment, an alternative would be to use the presence or absence of a single symbol. However, using absence of a symbol to designate nomenclatural status is potentially confusing because its absence may result from accidental omission. Furthermore, some readers may misinterpret absence of a symbol because they are unaware of the author’s convention.
Note 21.3A.2
If a symbol (e.g., quotation marks) is used to indicate non-monophyly of the taxon designated by the genus name, it would be redundant to indicate that the genus name is not an established clade name under this code.
Note 21.3A.3
If a symbol is used to indicate non-monophyly or questionable monophyly of the taxon designated by the genus name, 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 ICNAFP Article 36.1.
Recommendation 21.3B
When publishing the name of a new species, selection of a genus name will require consideration of the nomenclatural consequences under both the appropriate rank-based code and this code. In general, a genus name 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 genus name may be used, even if the monophyly of the associated taxon under the rank-based code is unknown or doubtful, or a new genus name may be used. If the species to be named cannot be assigned to any taxon with which a genus 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. 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., [P]) indicating that Sorex is an established clade name (see Rec. 21.3A, Ex. 1).
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 specific name or 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., [P]) indicating that Cladius is an established clade name (see Rec. 21.3A, Ex. 1). If this is done, Cladius should be validly published (ICNP, ICNAFP) 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., [nP]) indicating that Hypotheticus is not an established clade name (see Rec. 21.3A, Ex. 1) or a symbol (e.g., quotation marks) indicating that Hypotheticus is not monophyletic (see Note 21.3A.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., [nP]) indicating that Hypotheticus is not an established clade name (see Rec. 21.3A, Ex. 1) or a symbol (e.g., quotation marks) indicating that Hypotheticus is not monophyletic (see Note 21.3A.2). Alternatively, a new genus name 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 genus name has been associated under the appropriate rank-based code, it would be necessary to publish a new genus 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., [P]) indicating that Imaginarius is an established clade name (see Rec. 21.3A, Ex. 1).
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., [nP]) indicating that Imaginarius is not an established clade name (see Rec. 21.3A, Ex. 1).
21.4
Subsequent to a species binomen becoming available (ICZN) or validly published (ICNAFP, ICNP) under the appropriate rank-based code, the second part of the species binomen may be treated as the de facto name of the species under this code, termed a species uninomen. In this context, the species uninomen may be combined with the names of one or more clades the species is part of, in place of or in addition to the genus name (see Rec. 21A).
Recommendation 21.4A
When the genus name is used subsequent to the species binomen becoming available (ICZN) or validly published (ICNAFP, ICNP), some mechanism should be used to indicate whether the genus name is an established clade name under this code (see Rec. 21.3A, Ex. 1).
Recommendation 21.4B
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 (ICNAFP, ICNP), it should be accompanied by one or both of the following: (a) the genus name; (b) the author(s) and year of the publication in which the specific name (ICZN) or epithet (ICNP, ICNAFP) was validly published (ICNP, ICNAFP) or made available (ICZN).
Note 21.4B.1
Under the ICNAFP, 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 genus name 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 genus name is used, citation of the author and year of the specific name or epithet is optional.
Example 1
The species that is referred to as Vultur gryphus or Vultur gryphus Linnaeus 1758 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/gryphus Linnaeus 1758 or Aves/Vultur gryphus Linnaeus.
Recommendation 21A
When a species uninomen is combined with more than one genus name and/or clade name, 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 Recommendation 21.3A, Example 1 may be used with any of those names (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 genus 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 (e.g., 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 genus name, see Note 21A.3.
Note 21A.1
When a species uninomen is combined with a clade name that is not also a genus name, the uninomen can be viewed as a name in its own right, rather than as a modifier (adjectival or possessive) of the clade name. Consequently, the ending of the uninomen should not be changed to agree in gender or number (plural vs. singular) with the name with which it is combined. When a species uninomen is combined with a genus name, its gender may be changed to agree with that of the genus name.
Example 1
If the species uninomen sandiegensis is combined with the clade name Discodorididae, the uninomen should not be changed to sandiegensis to match the plural name Discodorididae.
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, Ex. 2), it is possible to provide phylogenetic information for a species without using a genus name that has not been established as a clade name under this code.
Note 21A.3
If a specific name (ICZN) or epithet (ICNP, ICNAFP) is associated with just one genus name, parentheses enclosing the name of the author and year of publication of the specific name (ICZN) or the author of the epithet (ICNP, ICNAFP) may be used to indicate that the specific name or epithet was originally combined with a different genus 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 categorical ranks under this code. Parentheses may also be used if a specific name or epithet is associated with just one clade name of suprageneric rank under the appropriate rank-based code.
Example 1
In the name Norops auratus (Daudin 1802), the use of parentheses indicates that Daudin originally published (made available; ICZN) the species name auratus in combination with a different genus 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, Ex. 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 genus name and that Bentham first validly published (ICNAFP) the binomen Physostegia virginiana.
Example 3
In the name Discodorididae sandiegensis (Cooper 1863) (see Rec. 21A, Ex. 2), the use of parentheses indicates that Cooper originally published the species name sandiegensis in combination with a different taxon name.