Botanical nomenclature provides every known species with a single, universally recognized scientific name. This standardization is necessary because relying on common names can lead to significant confusion, as the same plant may have multiple common names, or the same common name may refer to different species across various regions. Scientific names are structured within a hierarchy of ranks (e.g., Family, Genus, Species), and their formatting is governed by mandatory rules that ensure clarity and consistency. These rules dictate when a name must be capitalized or set in italics.
Formatting Rules for Plant Families
Plant family names are definitively not italicized under standard botanical nomenclature rules. Unlike the names for genus and species, which are set in a different typeface, the family name is presented in a standard, upright font, also called Roman type. This distinction serves as a visual cue regarding the specific taxonomic rank being discussed.
Plant family names are consistently capitalized because they function as proper nouns within the classification system. A family name represents a formal group of related genera, such as Rosaceae or Lamiaceae. The vast majority of formal plant family names are also required to end with the standardized Latin suffix “-aceae,” which signifies “resembling” or “belonging to.”
The “-aceae” suffix immediately identifies the term as a plant family name. For example, Rosaceae, derived from the type genus Rosa, signifies the family that includes roses and their relatives. A few long-standing exceptions exist, such as Fabaceae, which is also correctly known by the traditional name Leguminosae.
How Other Taxonomic Ranks Are Formatted
The formatting rules shift significantly for ranks below the family level, particularly for the genus and species, which form the basis of binomial nomenclature. This two-part naming convention is the most common scientific name encountered by the general public and requires the use of italics. The purpose of this italicization is to visually isolate the species name as a formal, Latinized scientific designation.
The genus name, the first part of the species name, is always capitalized and italicized. For example, in the name for the dog rose, Rosa canina, the genus is Rosa. The genus groups together closely related species that share common ancestry.
The second part of the species name, known as the specific epithet, is never capitalized but is always italicized. Continuing the example, canina is the specific epithet, resulting in the full species name Rosa canina. This italicized name is distinct from the non-italicized family name, Rosaceae.
Ranks above the family, such as Order (ending in -ales) and Class, follow the same formatting convention as the family name. These higher taxonomic groups are capitalized but are not italicized. The strict application of italicization is reserved for the genus, species, and infraspecific ranks.
The International Code Governing Plant Names
The specific formatting and naming conventions for all plant ranks are established and enforced by the International Code of Nomenclature for algae, fungi, and plants (ICNafp). This authoritative text was previously known as the International Code of Botanical Nomenclature (ICBN). The Code is amended and updated at International Botanical Congresses held approximately every six years.
The main purpose of the ICNafp is to ensure that the scientific naming of plants remains stable and universal across all nations and languages. By mandating rules for capitalization, suffixes, and the use of italics, the Code eliminates the potential for confusion that would arise if scientists adopted their own styles. Adherence to these specific formatting requirements is mandatory for all formal botanical publications.