Plant Classification and Nomenclature - PowerPoint Presentation

Slide1

Plant Classification and Nomenclature

Spring

2013

Slide2

Elements of UnderstandingBiological Diversity

Description

:

requires observation and measurement of characters and their states and synthesis of this information

Classification

:

requires hierarchical organization of taxa based on evolutionary relationships

Naming (nomenclature)

:

requires following nomenclatural conventions and enables communication

Identification

:

requires tools such as keys that are based on previous description, classification, and naming of taxa

Slide3

Elements of UnderstandingBiological Diversity

Description of Diversity

Classification of Diversity

Naming of Diversity

Naming of Diversity

Observation & Organization

Convention & Communication

Slide4

Description

Provides some basic identifiable set of characteristics to associate with the organism; also basis for characters and character states for phylogenetic analysis.

Can be as general or as detailed as practicality dictates.

Needs to contain enough data to provide adequate discrimination between similar organisms.

Needs terminology.

Descriptions are linked with a name when there is

consistency

in the set of observed characters for a given organism.

Slide5

Classification

A systematic arrangement in groups or categories according to established criteria; biological classification involves the delimitation, ordering and ranking of taxa.

Classification provides ORDER to the group of entities.

Relies on

observations

, many definable and comparable

characters

, and an ability to

discern

them.

Completely effective classifications can be

artificial

, that is, not necessarily reflecting evolutionary relationships: i.e., trees vs. shrubs vs. herbs.

But

modern classifications are based on evolutionary history

(phylogeny) because this provides predictive power and synthesis of many types of data is possible.

Biological classifications are hierarchical (= information storage system).

Slide6

Classification in Your Life…

Do you classify things?

Do you do it deliberately?

U

nconsciously?

Slide7

Let’s go home...*

In your room or apartment, think about what groups of items you automatically classify…

What characteristics and criteria do you use to do this?

Is the classification a continuous, ongoing thing, does it happen occasionally, or at very distinct times?

WHY do you do this?

*Mentally, that is – so just sit down and think…

Slide8

Some examples:

Kitchen:

- Silverware [knives, forks, spoons], plates, bowls, pots, pans, cooking utensils, trays, etc.

- Refrigerator – meats, vegetables, fruits, eggs,

bottles, cans, salad dressings, frozen foods.

Bedroom:

- Closet & dresser [shoes, boots, shirts, slacks, etc.]

- Jewelry

Living room:

- CDs, Video tapes/DVDs, books, magazines

Study:

- Textbooks, pens & pencils, paper, etc.

Slide9

A basic fact of life:

“Everyone is a Taxonomist”

Slide10

Artificial taxonomy

These classifications are based on use or similarity of shape.

Generally based on one or few “characters”.

Single character taxonomy may work in these situations, but…

Slide11

Single character taxonomy is bad taxonomy for biological systems.

Slide12

What makes a good classification?

- Groups recognized according to

overall similarity within groups

(as seen by multiple characters) and

discontinuities between groups

and

relatedness

(evolutionary history).

- The classification has

predictive value

– Characteristics of other related organisms can be predicted by the classification because of the evolutionary perspective.

- The classification is

practical

and

useful

.

Slide13

Why is biological classification possible?

Because variation exists in nature.

Four species of the bamboo genus

Chusquea

Slide14

Must be able to identify discrete “packages” of biological diversity: species.  Discontinuity is caused by: 1. evolution and speciation, or 2. extinction, or 3. a combination of 1. and 2.

Discontinuity of Biological Diversity

Slide15

To establish a classification, one must be able to use discontinuities to delimit groups at various hierarchical levels, e.g.: - How different are populations to warrant calling them distinct species? - How distinct are two groups to be able to recognize them as separate genera? Establishing ranks can be very subjective – the more objectivity we can impose on the process, the more reliable the classification.

Assessing Biological Discontinuity

Slide16

Speciation

Phylogeny

Evolutionary Time

Slide17

Speciation

Phylogeny

Effects of

Extinction

Slide18

Speciation

Apparent Phylogeny

Slide19

Hierarchical (nested) categories and phylogeny

PHYLUM

CLASS

ORDER

FAMILY

GENUS

TIME

Slide20

Phylogenetics

and Classification

Slide21

Principles of Biological Classification

Should be based on a well established hypothesis of relationships (a phylogeny) whenever possible

Ideally only recognizable (morphologically diagnosable) clades are formally named

Ranks should represent more or less equivalent branching points (but this is often ignored)

Slide22

Phylogenetics and Classification

Branching order can be inferred from the written classification.

Fig. 2.19A-C

Slide23

Classification

precedes

nomenclature!

Slide24

In terms of nomenclature, 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.

Slide25

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

Slide26

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

Slide27

Common name?

Whitlow grass

‘Real’ name:

Draba

verna

(

Brassicaceae

)

Slide28

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).

Slide29

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

Slide30

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

Slide31

Classification of Black Pepper

Kingdom Viridiplantae (Chlorobionta) Division/Phylum Anthophyta (Embryophyta) Class Magnoliopsida Subclass Magnoliidae (often not used now) Order Piperales Family Piperaceae Genus Piper Species Piper nigrum

Genus and species names are always italicized.

Slide32

All binomials have three parts…Piper nigrum L.

Species names are binomials!

Slide33

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

Slide34

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 Latinized (but Latin diagnoses or descriptions are no longer required)

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. 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.

Slide35

Fig. 16.2

Latin no

l

onger needed.

Slide36

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

Slide37

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

-A

ster

;

Poaceae

–

Poa

;

Lamiaceae

-

Lamium

.

Slide38

Type Specimen of Sobralia kerryae Dressler(Orchidaceae)

Holotype

Slide39

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 original

description when no

holotype

was designated by the author

Neotype

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

Slide40

Chusquea

latifolia

L. G. Clark

(Colombia)

Slide41

Slide42

Also common to

explain derivation

of name and to highlight

distinguishing

features as well as to

summarize distributionand habitat.

Slide43

Illustrations, maps,

and dichotomous

keys distinguishing

the new species from

related ones are

usually included.

Slide44

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.);

publication in electronic journals

is now also approved.

-

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.

Slide45

Why (and how) do

plant names change?

Slide46

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.

Slide47

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

Slide48

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.

Slide49

Synonyms - Priority

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

Malus

pumila

Miller, 1768

(invalid)

Malus

domestica

Borkh

., 1803

Malus

communis

Poiret

, 1804

(

SYNONYM

)

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

Slide50

Chusquea – 138 species

Neurolepis

– 21 species

Slide51

Molecular phylogeny of the subtribe Chusqueinae

C

S

R

N1

N2

▪

Spikelet structure▪Papillate subsidiary cells

▪Multiple, dimorphic buds

▪Connate lemma tips

*

*type species

*

Chusquea

Neurolepis

Slide52

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 and

Neurolepis

in 1843, so

Chusquea

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

Slide53

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)

Slide54

Are there similar examples

at the family level?

Slide55

Sapindaceae phylogeny(based on morphology; Judd et al. 1994)

SAP

HIPP

ACER

SAP

SAP

SAP

SAP

SAP

Chemistry

Appendaged

petals

Curved embryo w/

seed coat “pocket”

8 or fewer stamens

Etc.

Slide56

Sapindaceae

(traditional)

Aceraceae

Hippocastanaceae

Xanthoceraceae

(

X.

sorbifolium

)

Sapindaceae

molecular phylogeny

(

Buerki

et al. 2010)

?

Shares some but not all of the morphological

synapomorphies

shown on the previous slide.

Sapindaceae

i

n the broad

sense

Slide57

An example:Chusquea arachniforme L.G. Clark & Londoño was published in 1998Subsequently corrected to Chusquea arachniformis L.G. Clark & Londoño because the original form of the specific epithet was not correct in Latin

Nomenclatural Errors

Slide58

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:

X

Dialaeliocattleya

is an

intergeneric

hybrid of

Diacrium

,

Laelia

and

Cattleya

Slide59

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

’).

Slide60

Several databases help track all of this information

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

http://www.ipni.org/