Scientific Names and Related Terminology — An Introduction

Carl Linnaeus（圖片來源：Alexander Roslin，CC0 1.0 公共領域）

Recently there have been several discussions about changes in scientific names, which reminded me that we have not yet talked about how scientific names are actually used. This article therefore provides a brief introduction to several basic concepts surrounding scientific nomenclature. These ideas may prove useful when similar topics appear in future discussions.

To begin with the most fundamental point: scientific names must be written in Latin or in a Latinized form. There is no such thing as a "English scientific name." All English names are vernacular names. In addition, scientific names at the rank of genus and below are conventionally written in italics.

Here we will focus specifically on species-level names. Anyone familiar with Linnaeus's binomial nomenclature will recall that the scientific name of a species consists of two parts: the genus name and the specific epithet. For example, the Eurasian tree sparrow has the scientific name Passer montanus. In this case, Passer refers to the genus of sparrows, while montanus is the specific epithet.

The genus name is both part of the species name and also the formal name of the genus itself. The specific epithet, however, cannot exist independently. It must always appear together with the genus name. This leads to an important rule: the same specific epithet may occur in different species belonging to different genera, but genus names themselves cannot be duplicated. If two different genera shared the same genus name, it would create ambiguity whenever that genus was referenced. Therefore genus names must always be unique, while specific epithets are allowed to repeat because they are always paired with a genus name.

Scientific names are used to designate groups of organisms that share similar characteristics, whether those similarities arise from genetics, morphology, or reproductive relationships. However, classifications can sometimes be revised as new evidence emerges. For this reason, taxonomic names may be considered either valid or invalid.

A well-known example involves the domestic dog. The dog was once treated as a distinct species under the name Canis familiaris. Later research showed that although domestic dogs differ greatly from gray wolves in appearance, the genetic differences between them are relatively small and they are capable of interbreeding. These findings indicate that dogs do not meet the criteria required to be recognized as a separate species. As a result, Canis familiaris is now considered an invalid species name. Domestic dogs are currently classified as a subspecies of the gray wolf, written as Canis lupus familiaris. The use of three names instead of two indicates a subspecies designation. In other words, dogs are biologically a form of gray wolf.

Having introduced the idea of invalid classifications, we can now look at three common types of invalid scientific names.

1. Nomen dubium (dubious name) A nomen dubium refers to a name that is considered doubtful. This usually occurs when the available material is insufficient for reliable identification. In some cases the original type specimen—the reference specimen used to define the species—has been lost or destroyed. Without adequate material for comparison, it becomes difficult or impossible to determine whether newly discovered fossils belong to the same taxon.

2. Synonym (synonymy) A synonym arises when the same taxonomic group has been given two or more different scientific names. Several situations can produce this outcome. Sometimes different researchers independently name the same organism without realizing it has already been described. In other cases, taxonomic revisions merge previously separate groups into one. When multiple names exist for the same taxon, the earliest published name usually has priority. Returning to the previous example, Canis familiaris is now treated as a synonym of Canis lupus familiaris.

3. Nomen nudum (naked name) A nomen nudum is a scientific name that lacks a proper description. In order for a species name to be validly published, it must include a formal diagnosis describing its distinguishing features and must designate a type specimen. If these requirements are not met, the name is considered a nomen nudum. An interesting situation sometimes occurs when a species was originally described properly but the publication is later withdrawn—for example, if the research involved illegal fossil trafficking. When the paper is formally retracted, the name it introduced may lose its validity and become a nomen nudum.

These examples provide only a brief overview of how scientific names are used and interpreted. In reality, the rules governing biological nomenclature form a complex and fascinating system. For anyone who studies taxonomy or reads scientific literature closely, questions of naming and classification often lead to surprisingly intricate discussions. I remember that when I first began translating scientific papers, the section dealing with scientific names took the longest to understand. Perhaps we will explore more of these topics in the future.

Author: Bai Leng