Plant Nomenclature
Spring 2011
So far…
• We have been using names of plants to
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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 Understanding
Biological 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 Understanding
Biological Diversity
Description of Diversity
Observation & Organization
Classification of Diversity
Convention & Communication
Naming of Diversity
Classification
precedes
nomenclature!
What about common names?
• Positives:
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- 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
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information (and other species) are
discovered
It is helpful if names are descriptive
The International
Code of Botanical
Nomenclature
(ICBN) is the
“legal” code for
naming of plants.
A new version is
produced following
each international
botanical congress
(ca. every six years).
Principles of Nomenclature
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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
Plant Names
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)
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.
Species names are binomials!
All binomials have
three parts…
Quercus alba L.
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
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These steps must be followed in naming a new species, according to
the ICBN:
1. The name (specific epithet) must be in Latin or Latinized
2. 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 cited
5. 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
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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
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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
x
Type Specimen of
Sobralia kerryae Dressler
(Orchidaceae)
Holotype
Types by Rank
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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.
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Every species has a type specimen.
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Every genus has a type species.
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Every family has a type genus (and so on):
- Asteraceae -Aster; Poaceae – Poa; Lamiaceae Lamium.
Chusquea latifolia (Colombia)
Also common to
explain derivation
of name and to highlight
distinguishing
features.
Illustrations, maps,
and dichotomous
keys distinguishing
the new species from
related ones are
usually included.
Publication
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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) do
plant names change?
Plant names change when:
• The classification system has changed
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- 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.
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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 and
is the type of the currently accepted
species name in Capsella. The concept
of the species has not changed; only
its generic placement has changed.
Synonyms - Priority
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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
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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
Chusquea
▪Multiple, dimorphic
buds
*
C
S
R
▪Connate lemma
tips
▪Spikelet structure
▪Papillate
subsidiary cells
N1
*
N2
*type species
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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)
becomes
Chusquea elata (Kunth) L. G. Clark
Neurolepis pittieri McClure becomes
Chusquea magnifolia L. G. Clark
(a new name is needed because
the combination C. pittieri Hack. already exists)
Have we seen a similar example
at the family level?
Sapindaceae phylogeny
(based on morphology)
SAP
HIPP
SAP
SAP
SAP
SAP
Chemistry
Appendaged petals
Curved embryo w/
seed coat “pocket”
8 or fewer stamens
Etc.
SAP
ACER
Nomenclatural Errors
An example:
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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
Hybrid Taxa
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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
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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/