Nomenclature

Taxonomy of Flowering Plants - LECTURE NOTES - Spring, 1998 Hugh D. Wilson - rm. 306, Butler Hall 2 March 1998 Nomenclature

Nomenclature = the application or assignment of names. A major component of plant taxonomy. Why?

Names provide a cultural or symbolic link to reality and formal scientific names for flowering plants allow a connection to biological reality as expressed by complex systems of classification, i.e., scientific names provide a stable 'handle' and are also rich in information content.

The 220,000 species of Magnoliophyta are distributed world-wide. Plant Science is active on a world-wide basis - Chinese physiologists, German ecologists, American Agronomists, British Horticulturists are all working with plant material that can be identified, using the products of plant systematics, to a given species or infraspecific element. If scientific work is to be repeatable and communicated on a global basis, each species has to be associated with a symbol (species epithet) that is unique, standardized and, via the Genus name, intercalated into the full, content-rich system of botanical classification.

Problems encountered in the pre-scientific (or non-scientific) world:

1) applying different names to the same plant (independent, uncoordinated naming - analogy with naming bolt 'species' in the first lab)

2) applying the same name to different plants:

Buttercup
(East Texas)
Oenothera speciosa

Buttercup (elsewhere)
Ranunculus sp.

Local names for elements of a local flora are useful and valuable, but only on a local level. Many elements of a local flora have a broad distribution. Our 'Spanish Moss' (Tillandsia usneoides - which is Native American - not Spanish - and not a moss) is distributed throughout eastern North and South America, from Virginia to Argentina and it has many local names in several languages. It is however, a single biological entity and, as a result, it must have only one correct name.

3) coping with flux resulting from differences in taxonomic opinion (lumping vs. splitting)

Solutions have come about through cooperative development of an international system of plant nomenclature - brief history:

1) Carolus Linnaeus (overview from UC Berkeley) - initiated a standardized system in the mid-1700s and published SPECIES PLANTARUM (1753) which standardized the binomial as a replacement for descriptive names or polynomials:

before Linnaeus: Eupatorium cannabinum, foliis in caule ad genicula ternis, floribus parvis, umbellatim in summis caulibus dispositis, Marilandicum

after Linnaeus: Eupatorium purpureum

2) Augustin Pyramus de Candolle (French - photo from U. Maryland) made first attempt at an international code of nomenclature (early 1800s)

3) two codes existed in the late 1800s and early 1900s - American vs. European. Aspects of these were argued during international botanical congresses of 1892 and 1910.

4) 1930 - first International Code of Botanical Nomenclature (ICBN)

5) subsequent international botanical congresses (ca. every 4-6 years) hear proposals to modify the Code - the next congress is scheduled for 1999 (St. Louis, Missouri, USA)

6) each edition of the ICBN is published in English, French and German - the most recent (1994 - Tokyo Code) is available online

7) provisions of the ICBN are divided into Rules (firm or binding), set out in the Articles, and Recommendations (non-binding - suggestions)

PRINCIPLES:

1. "Botanical nomenclature is independent from zoological nomenclature"

2. The application of names of taxonomic groups is determined by means of nomenclatural types"

Each species has a nomenclatural type SPECIMEN, each genus has a species that serves as nomenclatural type, each family has a type genus, etc. THUS, the rank of species is the keystone of the nomenclatural system, i.e., the entire hierarchical structure is based on the species and its type specimen because this is the only physical link between the nomenclatural system - a cultural or symbolic construct - and biological reality. Why?

TYPE METHOD: Each species epithet is applied to a specific dried herbarium specimen - this represents the TYPE (HOLOTYPE = type designated by the authority, ISOTYPE = duplicate of the HOLOTYPE, LECTOTYPE = type specimen designated by a later worker. This specimen is the NOMENCLATURAL TYPE - a legalistic device, has nothing to do with the biology of the taxon. A given species is designated as nomenclatural type of a genus, a given genus is designated as nomenclatural type for the family. All changes in nomenclature resulting in taxonomic decisions concerning changes in RANK or CIRCUMSCRIPTION require examination of the type specimen. These specimens are of special interest and, as a result, are often receive special treatment by herbarium curators. See type specimen listings at the Texas A&M Tracy Herbarium (select Type Registry), the University of Texas Plant Resources Center (scroll to 'Type Register'), The Oregon State University Herbarium, Harvard University, and the New York Botanical Garden.

3. "The nomenclature of a taxonomic group is based upon the priority of publication".

PRINCIPLE OF PRIORITY: Example - What happens when three species are combined into a single unit (lumping):

    Cannabis sativa L. 1753
    C. indica Lam. (Jean Lamarck - 1744-1829) 1785
    C. ruderalis Janischevsky 1924

EARLIEST name is retained - C. sativa L. How far back do we go?
For vascular plants: Linnaeus' SPECIES PLANTARUM 1753 (MAY 1)
====================================================
REQUIREMENTS OF THE CODE FOR VALID PUBLICATION:

1. designation of a name
2. description (native language) and diagnosis (latin)
3. designation of a type:

Vernonia cronquistii S. B. Jones, sp. nov. TYPE: Cronquist 9705 (Holotype NY!, Isotypes: GH!; MEX!. [INDEX HERBARIORUM]

"EFFECTIVE" PUBLICATION = how published

4. "Each taxonomic group with a particular circumscription, position, and rank can bear only one correct name, the earliest that is in accordance with the rules, except in specified cases"

EXCEPTIONS = "CONSERVED" (for various reasons) names - at the Family level:

Palmae - Arecaceae
Gramineae - Poaceae
Cruciferae - Brassicaceae
Leguminosae - Fabaceae
Guttiferae - Clusiaceae
Umbelliferae - Apiaceae
Labiatae - Lamiaceae
Compositae - Asteraceae

5. "Scientific names of taxonomic groups are treated as Latin regardless of the derivation"

BINOMIAL: (species name) = COMPLETE SCIENTIFIC NAME

1. genus name - Singular, Latinized noun [or a word treated as a noun], always capitalized, often abbreviated [once written a single time], can be taken from any source - Marshalljohnstonia (information on genera - see Mabberley, D. J. 1997. The Plant-Book - copies in lab and Index Nominum Genericorum)

2. species epithet - can be derived from any source, often an adjective, descriptive, Latinized - (capitalization) - usually agrees in gender with the genus name

3. authority - full or abbreviated name = historical information. Who is the authority - see listings in Correll and Johnston, Manuel of the Vascular Plants of Texas, M. F. Fernald 1956. Manual of Botany or an online index from Harvard University. When and where was the name published? Indices are maintained as name references. These include the Gray Card Index (Harvard University) for New World taxa and also Index Kewensis (Royal Botanic Garden, Kew) - worldwide. Parenthetical authorities denote a change with retention of linkage to the individual (authority or author) responsible for the name:

CHANGE IN RANK - Smith does a study of the Vernonia cronquistii complex and discovers that plants assignable to V. cronquistii are closely related to V. alba - so: Vernonia alba L. ssp. cronquistii (S. B. Jones) Smith

CHANGE IN CIRCUMSCRIPTION White discovers that plants assignable to V. cronquistii are distinct from other Vernonia species, maybe with regard to chromosome number or gene sequences, and quite similar to species of Taraxacum - so - Taraxacum cronquistii (S. B. Jones) White

6. "all rules are retroactive unless expressly limited"

Why scientific names?

1. local or "common" names cannot be used on a world-wide basis because:

        many names per biological element across its range of distribution
        two or more plants can have the same local name, depending on location
        many species have no local name
        local names are 'language restricted'

2. as opposed to names applied via the ICBN, local or "common" names have no information content relative to the taxonomic system

For more info see: Plant Biology 250 (Plant Nomenclature)

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