Chapter Taxonomy and 5 Systematic Botany Plants are the prime companions of Learning Objectives human beings in this universe. Plants The learner will be able to, are the source of food, energy, shelter, clothing, drugs, beverages, oxygen and • Differentiate systematic botany from taxonomy. the aesthetic environment. Taxonomic • Explain the ICN principles and to activity of human is not restricted to discuss the codes of nomenclature. living organisms alone. Human beings • Compare the national and learn to identify, describe, name and international herbaria. classify food, clothes, books, games, • Appreciate the role of morphology, vehicles and other objects that they come anatomy, cytology, DNA sequencing across in their life. Every human being in relation to Taxonomy, thus is a taxonomist from the cradle to • Describe diagnostic features of the grave. families Fabaceae, Solanaceae, and Taxonomy has witnessed various Liliaceae. phases in its early history to the present day modernization. The need for knowledge Chapter Outline on plants had been realized since human existence, a man started utilizing plants 5.1 Taxonomy and Systematics for food, shelter and as curative agent for 5.2 Taxonomic Hierarchy ailments. 5.3 Concept of species – Morphological, Biological and Phylogenetic Theophrastus (372 – 287 BC), the 5.4 International Code of Botanical Greek Philosopher known as “Father of Nomenclature Botany”. He named and described some 500 5.5 Type concept plants in his “De Historia Plantarum”. Later 5.6 Taxonomic Aids Dioscorides (62 – 127 AD), Greek physician, 5.7 Botanical Gardens described and illustrated in his famous 5.8 Herbarium – Preparation and uses “Materia medica” and described about 600 th 5.9 Classification of Plants medicinal plants. From 16 century onwards 5.10 Types of classification Europe has witnessed a major developments 5.11 Modern trends in taxonomy in the field of Taxonomy. Some of the key 5.12 Cladistics contributors include Andrea Caesalpino, John 5.13 Selected Families of Angiosperms Ray, Tournefort, Jean Bauhin and Gaspard Bauhin. Linnaeus ‘Species Plantarum' (1753) 124 TN_GOVT_BOTANY_XI_Page 124-166 CH05.indd 124 02-06-2018 15:18:56 laid strong foundation for the binomial 5.1 Taxonomy and Systematics nomenclature. The word taxonomy is derived from Greek Taxonomy is no more classical words “taxis” (arrangement) and “nomos” morphology based discipline but (rules or laws). Davis and Heywood (1963) become a dynamic and transdisciplinary defined taxonomy as “the science dealing subject, making use of many branches of with the study of classification including botany such as Cell Biology, Physiology, the bases, principles, rules and procedures”. Biochemistry, Ecology, Pharmacology and Though there were earlier usages of also Modern Biotechnology, Molecular the term ‘systematics’, only during the Biology and Bioinformatics. It helps latter half of 20th century ‘Systematics’ to understand Biodiversity, Wildlife, was recognized as a formal field of study. Forest Management of natural resources Simpson (1961) defined systematics as for sustainable use of plants and eco “Scientific study of the kinds and diversity restoration. Differences between Taxonomy and Systematics Taxonomy Systematics • Discipline of classifying organisms into • Broad field of biology that studies the taxa. diversification of species. • Governs the practices of naming, • Governs the evolutionary history and describing, identifying and specimen phylogenetic relationship in addition to preservation. taxonomy. • Classification + Nomenclature = • Taxonomy + Phylogeny = Systematics Taxonomy of organisms and all relationships among tuberosus. These two species differ in their them”. Though there are two terms are morphology. Both of them are herbs but used in an interchangeable way, they differ Helianthus tuberosus is a perennial herb. from each other. Genus consist of multiple species which have similar characters but differ 5.2 Taxonomic Hierarchy from the species of another genus. Taxonomic hierarchy was introduced by Example: Helianthus, Tridax. Carolus Linnaeus. It is the arrangement Family comprises a number of genera of various taxonomic levels in descending which share some similarities among order starting from kingdom up to them. Example: Asteraceae. species. Order includes group of families Species is the lowest of classification which show less similarities among them. and shows the high level of similarities Class consists of group of orders which among the organisms. For example, share few similarities. Helianthus annuus and Helianthus 125 TN_GOVT_BOTANY_XI_Page 124-166 CH05.indd 125 02-06-2018 15:18:56 Division is the next level of classification Kingdom is the highest level or rank that consists of number of classes. of the classification. Example: Plantae Example: Magnoliophyta. Rank Ending Example Kingdom - Plantae Phylum = Division -phyta Magnoliophyta Subphylum = Sub division -phytina Magnoliophytina Class -opsida Asteropsida Sub class -idea Asteridea Order -ales Asterales Suborder -ineae Asterineae Family -aceae Asteraceae Sub family -oideae Asteroideae Tribe -eae Heliantheae Genus - Helianthus Sub genus - Helianthus subg. Helianthus Series - Helianthus ser. Helianthus Species - Helianthus annuus 5.3 Concept of species-Morphological, 3. In sexually reproducing organisms, Biological and Phylogenetic they interbreed freely in nature, Species is the fundamental unit of taxonomic producing fertile offspring. classification. Greek philosopher Plato 4. In asexually reproducing organisms, proposed concept of “eidos” or species and they are identified by their believed that all objects are shadows of the morphological resemblance. “eidos”. According to Stebbins (1977) species 5. In case of fossil organisms, they are is the basic unit of evolutionary process. identified by the morphological and Species is a group of individual organisms anatomical resemblance. which have the following characters. Species concepts can be classified into 1. A population of organisms which two general groups. Concept emphasizing closely resemble each other more than process of evolution that maintains the the other population. species as a unit and that can result in 2. They descend from a common evolutionary divergence and speciation. ancestor. 126 TN_GOVT_BOTANY_XI_Page 124-166 CH05.indd 126 02-06-2018 15:18:56 Another concept emphasises the product and recommendations of the International of evolution in defining a species. Code of Botanical Nomenclature. ICBN deals with the names of existing (living) Types of Species and extinct (fossil) organisms. The There are different types of species and elementary rule of naming of plants they are as follows: was first proposed by Linnaeus in 1737 1. Process of evolution - Biological Species and 1751 in his Philosophia Botanica. 2. Product of evolution - Morphological In 1813 a detailed set of rules regarding Species and Phylogenetic Species plant nomenclature was given by A.P.de Candolle in his famous work “Theorie Morphological Species (Taxonomic elementaire de la botanique”. Then the species) present ICBN was evolved by following the same rules of Linnaeus, A.P. de Candolle When the individuals are similar to one and his son Alphonse de Candolle. another in one or more features and different from other such groups, they are called morphological species. These ICBN due to specific reasons and in species are defined and categorized with order to separate plant kingdom from no knowledge of phylogenetic history, gene other organisms, is redesignated as flow or detailed reproductive mechanisms. ICN. The International Botanical Congress held in Melbourne in July Biological Species (Isolation Species) 2011 brought this change. The ICN According to Ernest Mayr 1963,“ these stands for International Code of are groups of populations that interbreed Nomenclature for Algae, Fungi and and are reproductively isolated from other Plants. such groups in nature”. ICN Principles Phylogenetic Species International Code of Nomenclature is This concept was developed by Meglitsch based on the following six principles. (1954), Simpson (1961) and Wiley (1978). Wiley defined phylogenetic species as “an 1. Botanical nomenclature is independent of zoological and bacteriological evolutionary species is a single lineage of nomenclature. ancestor descendent populations which maintains its identity from other such 2. Application of names of taxonomic group is determined by means of lineages which has its own evolutionary nomenclatural types. tendencies and historical fate”. 3. Nomenclature of a taxonomic group is based on priority of publication. 5.4 International Code of Botanical 4. Each taxonomic group with a particular Nomenclature circumscription, position and rank can bear only one correct name, the Assigning name for a plant is known as earliest that is in accordance with the Nomenclature. This is based on the rules rules except in specified cases. 127 TN_GOVT_BOTANY_XI_Page 124-166 CH05.indd 127 02-06-2018 15:18:56 5. Scientific names of taxonomic groups require the use of an identifier from are treated as Latin regardless of their a “recognized repository”. There are derivation. two recognized repositories Index 6. The rules of nomenclature are fungorum and Myco Bank. retroactive unless expressly limited. 19th International Botanical Congress was held in Shenzhen in China in 2017. Codes of Nomenclature Changes accepted by International ICN has formulated a set of rules and Botanical Congress are yet to be published.