Unit 3: Botanical Nomenclature

Binomial Nomenclature

Definition: This is the formal system of naming species, popularized by Carolus Linnaeus (in his 1753 work, Species Plantarum). Each species is given a two-part Latin name.

Example: Mangifera indica (Mango)

Rules:

1. The first part is the Genus name (e.g., Mangifera) and is always capitalized.
2. The second part is the specific epithet (e.g., indica) and is never capitalized.
3. The entire two-part name (the species name) must be italicized (if typed) or underlined separately (if handwritten).

ICN: Principles and Rules

ICN (International Code of Nomenclature for algae, fungi, and plants) is the set of rules and recommendations that govern the scientific naming of plants. The code is revised at each International Botanical Congress.

Key Principles of ICN

1. Botanical nomenclature is independent of zoological and bacteriological nomenclature.
2. The application of names is determined by means of nomenclatural types (typification).
3. Nomenclature is based upon the principle of priority of publication.
4. Each taxonomic group can have only one correct name (the earliest one that follows the rules).
5. Scientific names are treated as Latin, regardless of their origin.
6. The rules of nomenclature are retroactive (apply to past publications) unless expressly limited.

Ranks and Names

The ICN recognizes a hierarchy of ranks. The name endings (suffixes) are often standardized for specific ranks:

• Division (-phyta): e.g., Magnoliophyta
• Class (-opsida): e.g., Magnoliopsida
• Order (-ales): e.g., Rosales
• Family (-aceae): e.g., Rosaceae

Author Citation

This is the practice of citing the author(s) who first validly published the name. This is done to be precise and to avoid confusion.

• Example 1: Solanum nigrum L.
  The "L." stands for Linnaeus, who first named this species.
• Example 2: Pyrus calleryana Decne.
  "Decne." is the standard abbreviation for Decaisne.
• Example 3: (Genus) (Author 1) Author 2
  This means Author 1 first proposed the name, but Author 2 published a new combination or rank (e.g., moving a species to a new genus).

Typification

This is one of the most important principles of the ICN. Every scientific name is permanently attached to a single specimen, known as its nomenclatural type or "type specimen." This specimen acts as the definitive reference point for the name.

Publication, Priority, and Rejection

Effective and Valid Publication

For a new name to be officially recognized, it must be both effectively and validly published.

• Effective Publication: The name must be published in a widely distributed, printed medium (e.g., a scientific journal, a book). Publishing on a personal website or in a newsletter does not count.
• Valid Publication: The name must meet several criteria:
  1. Be effectively published (see above).
  2. Be in the correct Latin form.
  3. Be accompanied by a description or diagnosis of the taxon (in Latin or English).
  4. Designate a holotype.

Principles of Priority

Definition: This is the "first come, first served" rule. The correct name for a taxon (with a specific rank and circumscription) is the oldest (earliest) validly published name.

The starting point for this priority is Linnaeus's Species Plantarum (May 1, 1753).

Example: If Plantus A was named in 1800 and Plantus B was named in 1820, but they are later found to be the same species, the name Plantus A (the older one) is the correct name (or senior synonym), and Plantus B is rejected (as a junior synonym).

Rejection of Names

A name can be q (illegitimate) or rejected (invalid) if it breaks the rules. Common reasons:

• It was not validly published (e.g., no description or no type).
• It is a later homonym (a name that was already used for a different plant, e.g., Plantus B was already the name for a different species, so it cannot be used again).
• It is a junior synonym (a later name for a taxon that already had a valid name).
• It has been formally conserved against (to preserve a well-known name against an obscure, older name).

Naming New Taxa and Hybrids

Naming a New Taxon

To name a new species, a botanist must:

1. Discover and study the plant.
2. Confirm it is new and does not match any existing species.
3. Choose a new binomial name (Genus species).
4. Designate a holotype specimen.
5. Write a formal description (diagnosis) in Latin or English, highlighting its unique features.
6. Effectively publish this information (name, type, description) in a peer-reviewed journal.

Naming of Hybrids

The ICN also has rules for naming hybrids.

• Interspecific Hybrids (between two species): Can be given a "formula" (e.g., Verbascum lychnitis × V. thapsus) or a collective name. If given a name, it is preceded by a multiplication sign (×).
  Example: Verbascum × schiedeanum (this name applies to all hybrids between the two parent species).
• Intergeneric Hybrids (between two genera): A new "genus" name is created by combining the parent genera, preceded by a ×.
  Example: × Sorbopyrus (from Sorbus × Pyrus).