One of the most important goals of plant taxonomy is to develop a uniform, practical, and stable system of naming plants—one that can be used by both taxonomists and others needing a way to communicate information about plants. The internationally accepted system of giving scientific names to plants is set forth in the International Code of Botanical Nomenclature (Greuter et al. 1994), often referred to simply as the Code.
Why then do names keep changing? Names of plants are changed for three main reasons:
- There are changes due to legalistic reasons involving the accepted rules of nomenclature as outlined in the Code. For example, the oldest validly published name for a species must be used unless a later name is officially conserved (this is referred to as the “rule of priority”). While such changes may be inconvenient, without strict application of nomenclatural rules, scientific names would become as inexact and useless for communication as common names. It should be kept in mind that a particular plant species can have numerous common names in a small geographic area (e.g., a state) and dozens of different common names in different languages and different countries.
- There are changes resulting from shifts in taxonomic philosophies, such as those exemplified by “splitters” and “lumpers,” or the rejection of paraphyletic groups (for more details see the appendix on Taxonomy, Classification, and the Debate about Cladistics).
- Most important, however, are those changes resulting from an increased understanding of the plant species themselves. Initial hypotheses on what species exist, and what their diagnostic characteristics are, are sometimes based on a limited number of specimens, little or no experience with the species in the field, and little additional information. These hypotheses are tested whenever more specimens become available for examination, when field work is carried out, or when additional studies are done (including molecular studies, electron microscopy, breeding studies, etc.). Sometimes the initial hypotheses are supported and no name changes are necessary. In other instances the hypotheses need to be modified to reflect the new evidence (e.g., a plant actually belongs in a different genus). This in turn can affect the scientific nomenclature. On-going name changes therefore do not indicate simple equivocation on the part of taxonomists, but rather are an accurate reflection of the dynamic nature of our scientific understanding of the plant kingdom.
In order to minimize the impact of nomenclatural changes on users of this book, we have typically given taxonomic synonyms (particularly commonly used ones) for those species whose names have changed in the recent past. Such synonyms can be found in brackets, [ ], near the end of the species treatments and can be reached using the index.
This writeup was modified from one written by B. Ertter (pers. comm.).