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Because the ICBN is a concensus document (that is, not governed by a commission, or with binding penalties), the Principles are really guiding hopes.

Principle I. Botanical nomenclature is separate from zoological (or bacterial), so the same name can be given to plants and animals

Example: Cecropia, moth genus vs. Cecropia, genus of plants

A. Cyanobacteria and Myxomycetes are specifically covered under ICBN, even though they are acknowledged not to be plants

Example: In publications dealing with the cellular slime molds, Lindsay Olive used the zoological code OR the botanical code, dictated by the journal in which he was publishing

B. PLACEMENT of the organism vs. TREATMENT of the organism name. If the name is TREATED as a plant, it falls under ICBN.

Example: Certain protozoa can be treated as though they were animals, or treated as though they were plants.

C. These days, insertion on a phylogenetic tree constitutes placement, but if the pertinent literature on the organism treats it as a plant, then nomenclature must follow taxonomy, and the NAME should follow the ICBN.

Principle II. NOMENCLATURAL types may not conform to TAXONOMIC (or "biological") "types." The nomenclatural type is always the element (i.e. specimen, species, genus, etc.) to which the basionym of the taxon was attached. The ICBN does not deal with taxonomic (or biological) types.

Example: The nomenclatural type of Clavulinopsis van Overeem is C. sulcata, explicitly stated by van Overeem (1923). The type specimen is at BO, and the genus was monotypic.Placement of C. sulcata as a synonym under Clavaria miniata Berk. made the correct name of the organism Clavulinopsis miniata (Berk.) Corner, and made this name the taxonomic type of Clavulinopsis.  Reid found that C. sulcata and Clavaria miniata were different organisms, thus requiring reversion to the nomenclatural type, which had never changed.

Principle III. Although PRIORITY is the only factor named here, there is a hierarchy of filters through which all names must pass, priority being only the last.

Principle IV. CIRCUMSCRIPTION, POSITION, and RANK create parameters for names.

CIRCUMSCRIPTION: This is a taxonomic process, not nomenclatural. It is the taxonomist's obligation to group all specimens and populations (often represented by herbarium specimens) of a plant group in order to arrive at a conclusion about the taxonomic scope of variability in the plant group, and to segregate OPERATIONAL TAXONOMIC UNITS ("OTUs," a term usually used to denote branch tips on phylogenetic trees but here used merely as a nondenominational designation for the piles of specimens surviving after the sorting process, whether these piles are the result of DNA sequence data or phenetic analysis or intuition). Once the number of OTUs is clear and comfortable in the taxonomist's mind, each group can be characterized, or circumscribed (i.e. a thorough description compiling ALL characters of the group, whether taxonomically informative or not). What results from this process is a series of CIRCUMSCRIPTIONS. (Parenthetically, the ICBN dictates that each OTU shall be typified).

POSITION: During the process, the taxonomist will usually arrive at a judgement about the taxonomic placement of the OTUs (i.e. into what order, family, tribe, genus, etc. they should be placed). The result of this judgement constitutes the POSITION of the OTUs.

RANK: During the process, some judgement must be made about the relative nomenclatural rank (i.e. variety, species, subfamily, etc.) of each OTU. Some OTUs may be judged as only a form of a species, while others may be judged so separated from others as to constitute species. The result of this process is the RANK of each OTU.

The result of the whole process is a group of OTUs for which the taxonomist has thorough descriptions (i.e. circumscriptions), placement within higher level taxa (i.e. position) and relative ranks. Only after the entire process is completed should a correct name be sought based on these three guiding principles.


Overholts Kotlaba & Pouzar Donk
Lenzites betulina Lenzites betulina Lenzites betulina
Lenzites trabea Phaeocoriolellus trabeus Gloeophyllum trabeum
Lenzites saepiaria Gloeophyllum saepiarium Gloeophyllum saepiarium
Trametes odorata Osmoporus odoratus Gloeophyllum odoratum

Other charts could be constructed by changes in rank. Circumscription, however, also includes taxonomic and typification decisions.

Principle V. The key word here is TREATED. Older codes urged avoidance of "barbarous tongues," which meant, of course, everything except English and European languages.

Principle VI. Almost all chapters include restrictive dates, so very few rules are totally retroactive.

edible mushroom2.jpg (4427 bytes)   Agaricus