Plant Nomenclature

Spring 2011

So far…

• We have been using names of plants to discuss their “position” in the plant kingdom, reflecting some level of evolutionary understanding.

• The names for plant species or genera have been used as a “given” – that is, we did not talk about how those names came into being or how they are correctly used.

• We need to understand how the accepted system of nomenclature works – how the giving of names to plants follows a specific set of guidelines and rules.

Elements of UnderstandingBiological Diversity

Discovery of Diversity: Field work, study of existing specimens

Description of Diversity: Phytography – Facilitates communication

Classification of Diversity: Should reflect what we know about phylogeny, to the extent possible

Naming of Diversity: Nomenclature – Giving scientific names according to an accepted naming system

Elements of UnderstandingBiological Diversity

Description of Diversity

Classification of Diversity

Naming of DiversityNaming of Diversity

Naming of Diversity

Observation & Organization

Convention & Communication

Classification

precedes

nomenclature!

What about common names?

• Positives:- easily recognizable- easier to pronounce and spell (!)

• Negatives:- Name varies by language or region- Not specific (ironwood, bigleaf, ivy, etc.)- Conveys no evolutionary information- Does not include classificatory information

• Botanists rely on the ‘botanical’ or scientific name for accurate communication about the plant in question

Common name?

Whitlow grass

‘Real’ name:Draba verna(Brassicaceae)

Naming and Nomenclature• Plants did not evolve with a name! • However, we need names to communicate

about the plant• Organized system of names enables fitting

the plant into an accepted scheme• Following formal naming rules =

nomenclature• The system must allow for changes as new

information (and other species) are discovered• It is helpful if names are descriptive

The InternationalCode of BotanicalNomenclature(ICBN) is the“legal” code fornaming of plants.

A new version is produced followingeach internationalbotanical congress(ca. every six years).

Principles of Nomenclature• Botanical and zoological classification systems are

independent of one another • Applying names to taxonomic groups is based on a

system of nomenclatural types• Names are based on the priority of publication – the

earliest valid name is the one to use (later names for the same taxon are called synonyms); starting point for plants is Linnaeus’s Species Plantarum (1753)

• Each taxon can have only one correct name• Scientific names are in Latin or are treated as

Latinized words, regardless of origin• Rules of nomenclature (ICBN) are retroactive unless

expressly limited

An exception to the rule that there is only ONE legitimate name per taxon:

Eight angiosperm families have two acceptable names: (Arecaceae = Palmae; Apiaceae = Umbelliferae; Asteraceae = Compositae; Brassicaceae = Cruciferae; Clusiaceae = Guttiferae;

Fabaceae = Leguminosae; Poaceae = Gramineae)

Plant Names

Classification of Black Pepper

Kingdom Plantae (Viridiplantae)

Division/Phylum Anthophyta (Embryophyta)

Class Magnoliopsida (Angiospermopsida)

Subclass Magnoliidae

Order Piperales

Family Piperaceae

Genus Piper

Species Piper nigrum

Genus and species names are always italicized.

All binomials have three parts…

Quercus alba L.

Species names are binomials!

Piper nigrum L. = Black Pepper

Piper – Genus name or generic epithet – Member of the genus Piper

nigrum – Species epithet – Latin for ‘black’

L. = Linnaeus – Author – Person who described plant

Black Pepper – Common name

Naming a New Species• These steps must be followed in naming a new species, according to

the ICBN:1. The name (specific epithet) must be in Latin or Latinized2. The rank of the new name must be clearly indicated (in this case, species novum or new species)3. A type specimen must be designated (including the herbarium where it is deposited)4. A diagnosis or description in Latin must be provided or a reference in which a Latin description for this taxon appears must be cited5. All of this information and any additional material (e.g., illustrations) must be effectively published (presented in a publication that is widely available to other botanists)

Following all of these steps results in valid publication of the name. The process of describing a new species can take a year or more, depending on what studies are needed to justify it as a new species, how long it takes to prepare illustrations and keys, and which journal or book it is published in.

The Type System• Each species name must be based on a type specimen, with

which the name is permanently associated.• Types are preserved as reference specimens, often kept

separately from the remaining collections in the herbarium.• The type specimen must fit within the concept of the species,

but does not necessarily have to be representative of average variation (i.e., it may represent one of the extremes of variation in the species)

• The species name used for the type specimen is considered the basionym, or original name as described, and follows that specimen in perpetuity

• Names of higher ranks are based on typified names published validly and effectively

Botanical Types• Holotype – The one specimen (or illustration)

designated by the author that will serve as the nomenclatural type

• Isotype – A duplicate of the holotype (part of the same gathering); always a specimen

• Lectotype – The specimen designated as the nomenclatural type if no holotype is available or indicated by the author

• Syntype - Any specimen that is cited in the protologue when no holotype was designated by the author

• Neotype – A ‘new’ type specimen designated when all material for the original type description is missing

Type Specimen of Sobralia kerryae Dressler

(Orchidaceae)

x

Holotype

Types by Rank

• The type is one physical specimen deposited in an herbarium to which the name is attached and upon which the species description is based (holotype); the holotype can be an illustration although this is unusual.

• Every species has a type specimen.

• Every genus has a type species.

• Every family has a type genus (and so on):- Asteraceae -Aster; Poaceae – Poa; Lamiaceae - Lamium.

Chusquea latifolia (Colombia)

Also common to explain derivationof name and to highlightdistinguishing features.

Illustrations, maps,and dichotomous keys distinguishingthe new species fromrelated ones areusually included.

Publication• Names of new taxa must be published effectively

and validly to have recognition in the systematics community under ICBN:

- Effective Publication – The information must be published in a recognized botanical journal or book (…not a seed catalog or newspaper, internet, etc.).

- Valid Publication – All of the conditions laid out in the ICBN have been met, including effective publication.

- The new name is considered to be a legitimate name if all of the correct publication conditions are met. Whether the name becomes accepted (or not) depends on how the botanical community agrees with the author.

Why (and how) doplant names change?

Plant names change when:

• The classification system has changed - By far the more typical and frequent cause

of name changes- New data often support revision of concepts of generic, familial, or other circumscriptions, necessitating name changes

• Because of nomenclatural errors- Errors made in original descriptions or taxonomic revisions may need to be corrected by changing the names of plants due to improper format, invalid publication, etc.

Capsella bursa-pastoris (L.) Medik.

Capsella bursa-pastoris (L.) Medik.

• Original Description- Described by Linnaeus as Thlaspi bursa pastoris L., because the species fit in his concept of Thlaspi- Placed as one species in genus Thlaspi, but was not the first species described in the genus (that was T. arvense L.)

• Subsequent Revision of Taxonomy- Friedrich Kasimir Medikus (Dir. Botanisches Garten Mannheim) thought the species should be placed in a separate genus, which he named Capsella in 1792-The specific epithet must be retained in such a transfer and the original name becomes a synonym

• This is an example of a taxonomic transfer. The author names reflect the history of publication of the original species name (basionym) and the subsequent transfer to a new genus

Capsella bursa-pastoris (L). Medik.

Syn.: Thlaspi bursa pastoris L. basionym

The type specimen of the basionym(original name) stays the same andis the type of the currently acceptedspecies name in Capsella. The conceptof the species has not changed; onlyits generic placement has changed.

Synonyms - Priority

• If two (or more) different names are determined to be the same entity, the earliest validly and effectively published name has priority = SYNONYM

– Malus pumila Miller, 1768 (invalid) – Malus domestica Borkh., 1803 – Malus communis Poiret, 1804

• If the same name has been used for more than one taxon, these are considered HOMONYMS.– Platonia Raf. 1810 is a genus of Cistaceae (rock rose

family)– Platonia Kunth 1829 is a genus of Poaceae (bamboo);

this name was changed to Neurolepis Meisn. in 1843

Chusquea – 138 species

Neurolepis – 21 species

Maximum parsimony, combined data sets

C

S

R

N1

N2

▪Spikelet structure▪Papillate subsidiary cells

▪Multiple, dimorphic buds

▪Connate lemma tips

*

*type species

*

?

Chusquea

Neurolepis

What to do?

• Neurolepis is paraphyletic to Chusquea• Neither N1 nor N2 has synapomorphies• All clades share the same spikelet and flower

structure• Chusquea Kunth was published in 1822, so it is

the older generic name• So, we synonymized Neurolepis with Chusquea;

all of the species formerly in Neurolepis received new combinations or new names in Chusquea

Neurolepis elata (Kunth) Pilg.(basionym Platonia elata Kunth)becomesChusquea elata (Kunth) L. G. Clark

Neurolepis pittieri McClure becomesChusquea magnifolia L. G. Clark(a new name is needed becausethe combination C. pittieri Hack. already exists)

Have we seen a similar exampleat the family level?

Sapindaceae phylogeny (based on morphology)

SAP

HIPP

ACER

SAP

SAP

SAP

SAP

SAPChemistryAppendaged petalsCurved embryo w/ seed coat “pocket”8 or fewer stamensEtc.

An example:

• Chusquea arachniforme L.G. Clark & Londoño was published in 1998

• Subsequently corrected to Chusquea arachniformis L.G. Clark & Londoño because the original form of the specific epithet was not correct in Latin

Nomenclatural Errors

Hybrid Taxa

• Hybrids are indicated with the "X" sign and may be given in two forms, the first where the parental taxa are indicated, the second where the hybrid taxon is given a new name:

Quercus alba L. X Q. michauxii Nutt. -or -Quercus X beadlei Trelease

• Hybrid genera (a nothogenus) are indicated by an X before the name, which is composed of elements of the contributing parental genera: XDialaeliocattleya is an intergeneric hybrid of

Diacrium, Laelia and Cattleya

Cultivar Names

• Cultivated plants follow a “related” code of horticultural nomenclature

• Examples of correct cultivar names of apple, Malus baccata Borkh.:– M. baccata var. mandschurica Schneider – M. baccata cv. Columnaris – M. baccata 'Jackii' – Malus 'Barbara Ann'

• Cultivar Names: First letter capitalized, not Latinized (thus, not italic), preceded by cultivar abbreviation (cv.), or in single quotes (‘Jackii’).

Several databases help track all of this information

http://www.tropicos.org/Home.aspx

http://www.ipni.org/