Plant Names and Classification

Plant Names and Classification

Chapter 16

Outline Introduction Development of the Binomial System of

Nomenclature• Linnaeus• The International Code of Nomenclature for Algae,

Fungi, and Plants Development of the Kingdom Concept Classification of Major Groups The Species Concept

Introduction All living organisms given two-word Latin scientific name

= species name• Only one correct scientific name for species• Many common names may be given to same species

− Dicentra cucullaria - 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 applied to number of different species

− Monkshood for Dicentra cucullaria and Aconitum species

Development of the Binomial System of Nomenclature

1st attempt to organize/classify plants - Theophrastus (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)

Development of the Binomial System of Nomenclature

• Published Species Plantarum, 1753

• Changed Latin phrases to reflect relationships and placed one to many species in each genus

− Abbreviated names to 2 parts (binomials)

Carolus Linnaeus (1707–1778) - established Binomial System of Nomenclature

Development of the Binomial System of Nomenclature

Binomial System of Nomenclature• All species named

according to this system, includes authority for species name

− Spearmint: Mentha spicata L.

A page from

Species Plantarum

by Linnaeus

The International Code of Nomenclature for algae, fungi, and plants

Book standardizes rules governing naming and classification of plants• Linnaeus starting point for names• Rules revised and expanded at periodic international

botanical congresses• Has English, French and German translations• Requires 2 steps to officially recognize new plant

species:− English or Latin description or diagnosis must be

published in journal or other public publication− Author must designate type specimen deposited in

herbarium

Development of the Kingdom Concept When classification schemes first developed,

organisms placed in either Plant Kingdom or Animal Kingdom• Distinction works well for complex animals, but not

for simpler organisms

Hogg and Haeckel proposed 3rd kingdom in 1860’s• All organisms that did not develop complex tissues

placed in Kingdom Protoctista

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 5-kingdom system• Split Fungi from Kingdom Protista

In 1980s, Woese argued Monera should be split into Archaea and Bacteria, resulting in 6 kingdoms• Archaea, Bacteria, Protista, Fungi, Plantae, Animalia

Classification of Major Groups

3 domains: Bacteria, Archaea, Eukarya

Depending on classification system, between 12-30 plant phyla recognized

In-between categories, such as subphylum, subclass, suborders subspecies, varieties and forms also used

Classification of Major Groups 1st part of species name = genus 2nd 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

The Species Concept Morphological species concept - species

defined by morphology

Interbreeding species concept - species a population capable of interbreeding and reproductively isolated from other groups

Ecological species concept - species a group of related individuals that occupy unique ecological niche

The Species Concept Cladistic species concept - species determined by

phylogenetic history• Individuals with common evolutionary background =

species− Cladistic methods used to determine evolutionary

historyExamines natural relationships among organisms,

based on shared featuresRelationships portrayed on cladogramsValue or form of feature referred to as character

stateHypotheses made about which state ancestral

The Species Concept In trying to choose 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 interpreted as that which requires fewest evolutionary changes in taxa involved

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 local interbreeding

population

Review Introduction Development of the Binomial System of

Nomenclature• Linnaeus• The International Code of Nomenclature for Algae,

Fungi, and Plants Development of the Kingdom Concept Classification of Major Groups The Species Concept