1. Plant Names and Classification
Chapter 13
Lecture Outline
Plant Names and Classification
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2. Outline
Introduction
Development of the Binomial System of Nomenclature
Linnaeus
The International Code of Botanical Nomenclature
Development of the Kingdom Concept
Classification of Major Groups
The Species Concept

3. Introduction
All living organisms given two-word Latin scientific name = species name.
Only one correct scientific name for a species.
Many common names may be given to same species.
Dicentra cucullaria - Many common names: Dutchman’s breeches, little-boy’s breeches, monkshood, boys-and-girls, soldier’s cap, white hearts,…, plus others in different languages
Or one common name may be applied to a number of different species.
Monkshood is common name for Dicentra cucullaria and for Aconitum species, which is in a different family.

4. Development of the Binomial System of Nomenclature
First attempt to organize and classify plants by Theophrastus in 4th century B.C.
Classified nearly 500 plants by leaf characteristics
13th century - Distinction made between monocots and dicots.
Beginning of 18th century - Details of fruit and flower structure, in addition to form and habit, used in classification schemes.
Latin phrase name given to plants and animals.
First word of phrase indicated genus (plural: genera).

5. Development of the Binomial System of Nomenclature
Carolus Linnaeus (1707–1778) - Established Binomial System of Nomenclature
Published Species Plantarum, 1753
Changed the Latin phrases to reflect relationships and placed one to many species in each genus
Abbreviated names to two parts (binomials)

6. Development of the Binomial System of Nomenclature
All species named according to this system, which includes authority for species name.
Spearmint: Mentha spicata L.

7. The International Code of Botanical Nomenclature
Book that standardizes rules governing the naming and classification of plants
Agreed that Linnaeus is starting point for names
Rules revised and expanded at periodic international botanical congresses.
Has English, French and German translations
Requires two steps to officially recognize new plant species:
Latin description of plant must be published in a journal or other public publication.
Author must designate type specimen that is deposited in a herbarium.

8. Development of the Kingdom Concept
When classification schemes first developed, organisms placed in either Plant Kingdom or Animal Kingdom.
The distinction works well for complex animals, but not for simpler organisms.
Hogg and Haeckel proposed a third kingdom in 1860’s.
All organisms that did not develop complex tissues were placed in Kingdom Protoctista.

9. Development of the Kingdom Concept
In 1938, Copeland assigned single-celled, prokaryotic organisms to Kingdom Monera, leaving algae, fungi and single-celled eukaryotic organisms in Protoctista.
In 1969, Whittaker developed five-kingdom system.
Split Fungi from Kingdom Protista
In 1980s, Woese argued Monera should be split into Archaea and Bacteria, resulting in six kingdoms:
Archaea, Bacteria, Protista, Fungi, Plantae, Animalia

11. Classification of Major Groups
Genera grouped into families.
Families grouped into orders.
Orders grouped into classes.
Classes grouped into phyla (divisions).
Phyla grouped into kingdoms.
Example: onion
Kingdom: Plantae
Phylum: Magnoliophyta
Class: Liliopsida
Order: Liliales
Family: Liliaceae
Genus: Allium
Species: Allium cepa L.

12. Classification of Major Groups
3 domains (super- kingdoms): Bacteria, Archaea, Eukarya
Depending on the classification system, between 12 and 30 plant phyla recognized.
In-between categories, such as subphylum, subclass, and suborders used; and species sometimes further divided into subspecies, varieties and forms.

13. Classification of Major Groups
Second part of species name = specific epithet.
Specific epithet followed by author(s) who named the plant.
Taxonomists specialize in identifying, naming, and classifying organisms.
Systematists incorporate evolutionary processes to sort out natural relationships.
Dichotomous keys help identify organisms.
Choose features from paired statements that most closely apply to organism

14. The Species Concept
Morphological species concept - A species is defined by morphology.
Interbreeding species concept - A species is a population capable of interbreeding and is reproductively isolated from other groups.
Ecological species concept - A species is a group of related individuals that occupy a unique ecological niche.

15. The Species Concept
Cladistic species concept - A species is determined by phylogenetic history.
Individuals with common evolutionary background considered to be a species.
Cladistic methods used to determine evolutionary history.
Examines natural relationships among organisms, based on shared features.
Relationships portrayed on cladograms.
The value or form of a feature referred to as a character state.
Hypotheses made about which state is ancestral.

16. The Species Concept
In trying to choose the best cladograms, taxonomists use principle of parsimony.
Occam’s razor - “One should not make more assumptions than the minimum needed to explain anything.”
Best cladogram is interpreted as that which requires fewest evolutionary changes in taxa involved.

18. The Species Concept
Eclectic species concept - Single criterion not sufficient to identify species.
Morphological, geographical, biological and ecological criteria must be used when defining species.
Nominalistic species concept - Species do not exist.
Evolutionary unit of importance is local interbreeding population.

19. Review Introduction Development of the Binomial System of Nomenclature
Linnaeus
The International Code of Botanical Nomenclature
Development of the Kingdom Concept
Classification of Major Groups
The Species Concept