Plant Names and Classification Chapter 16 Lecture Outline Plant Names and Classification Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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

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.

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).

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)

Development of the Binomial System of Nomenclature All species named according to this system, which includes authority for species name. Spearmint: Mentha spicata L. A page from Species Plantarum by Linnaeus

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.

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.

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

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.

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.

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

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.

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.

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.

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.

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