Basionyms in Biological Nomenclature: Rules and Applications
In the precise world of biological classification, names are not static. As scientific understanding evolves, species are often moved between genera or reassigned to different taxonomic ranks. To maintain a clear historical record of these changes, taxonomists use a system centered around the basionym.
A basionym is the original name on which a new name is based. Whether in botany or zoology, the basionym serves as the permanent anchor for a taxon, ensuring that the original description and type material remain linked to the organism, regardless of how many times its name changes over the centuries.
Key Facts
- Basionym: The original name used as the basis for a new taxonomic combination or rank.
- Author Citation: The original author of the basionym is placed in parentheses in the new name's citation.
- Direct Reference: New names must be based on the original basionym, not on intermediate name changes.
- Typification: A new combination is typified by the original type specimen of the basionym.
- Terminology: While botany and zoology use "basionym," bacteriology uses the term "basonym."
Basionyms vs. Protonyms
While often used interchangeably, there is a technical distinction between a basionym and a protonym. A protonym refers to the original spelling of the original name. In contrast, a basionym is the correct spelling of that original name according to the applicable nomenclature rules. In most cases, these are identical, but they can differ in rare instances where the original spelling was incorrect.
Rules for Creating New Taxonomic Names
To prevent confusion and maintain a transparent chain of nomenclature, strict rules govern how basionyms are applied. When a species is transferred between multiple genera over time, each new combination must refer back to the original basionym rather than any intermediate combinations.
The Role of Type Specimens
Because a new combination is typified by the type of its basionym, all original material must originate from the basionym. Taxonomists cannot designate a lectotype (a type specimen selected after the original description) from specimens used only in a later combination. If no original material exists, a neotype may be designated instead.
Replaced Synonyms
Sometimes, a replacement name is necessary even if a legitimate name exists. This occurs if a new combination would create an illegitimate homonym (a duplicate name) or if the name cannot be validly published due to rules against tautonyms (where the genus and species names are identical).
Application in Botany
In botany, the use of basionyms is regulated by the International Code of Nomenclature for algae, fungi, and plants (ICNafp). A basionym must be legitimate and provide a useful description, which exempts the author of the new name from providing a full description again.
Historically, these rules have tightened. Before January 1, 1953, indirect references to a basionym were sufficient for valid publication. After this date, the code required more explicit references to ensure accuracy.
Practical Examples: Combinatio Nova and Status Novus
Combinatio Nova (New Combination)
A combinatio nova (abbreviated as comb. nov.) occurs when a species is moved to a different genus. For example, the Norway spruce was originally named Pinus abies by Carl Linnaeus (cited as "L."). Later, Gustav Karl Wilhelm Hermann Karsten moved it to the genus Picea. The resulting name, Picea abies (L.) Karst., credits Linnaeus in parentheses as the basionym author and Karsten as the author of the new combination.
Status Novus (New Rank)
A status novus (abbreviated as stat. nov.), or "name at new rank," occurs when a taxon is moved to a different taxonomic level. In 1964, Claude Weber changed the rank of a group within the Rosaceae family from family (Malaceae Small) to subfamily (Maloideae), referring back to the original description and type.
Summary of Taxonomic Terms
| Term | Definition | Key Characteristic |
|---|---|---|
| Basionym | The original name on which a new name is based. | Must be the correct spelling. |
| Protonym | The original spelling of the original name. | The literal first spelling used. |
| Combinatio Nova | A new combination of genus and species. | Moves a species to a new genus. |
| Status Novus | A name at a new taxonomic rank. | Changes the level (e.g., family to subfamily). |
| Basonym | The bacteriological equivalent of a basionym. | Spelled without the "i". |
Frequently Asked Questions
How is the author of a basionym cited in a new name?
The author of the basionym is placed in parentheses at the beginning of the author citation, followed by the author who created the new combination.
What happens if a basionym is found to be illegitimate?
If a basionym is deemed illegitimate, it becomes a replaced synonym. In this case, the author citation of the current name must be updated to remove the basionym authors.
Can a taxonomist use a recent name as a basis for a new one?
No. A new combination or name at a new rank must be based directly on the original basionym, not on any intermediate combinations that occurred in between.
What is the difference between a lectotype and a neotype in this context?
A lectotype is a specimen selected from the original material of the basionym. A neotype is only designated if no original material from the basionym exists.
Do the same basionym rules apply to bacteria?
Yes, bacteriology uses a similar system, though the term is spelled "basonym" (without the "i").