Plant Classification Systems PDF

 Greek words Taxis – Arrangement Nomos – Rules or laws What systematic does! Identifies...

 Greek words Taxis – Arrangement Nomos – Rules or laws What systematic does! Identifies Describes Nomenclature Constructing affinities A.P. de Candolle (1813) IDENTIFICATION Taxonomy is a science dealing with Assigning correct rank classification, including its bases, and position and give its principles, rules and procedure classification Systematics is the study of How do we do it? diversity of organisms and study of Herbaria relationships between them. Literature Monographs and Modern days taxonomy and Manuals systematics are synonymous DESCRIPTION NOMENCLATURE Diagnostic description is written It deals with determination of which will involve in determining correct name for the taxon. Nomenclature of the plants is its circumscription. For this plant usually governed by character and character states 1) ICBN: International code for have to be listed. Botanical Nomenclature. 2) ICNCP – International code for nomenclature for cultivated plants CONSTRUCTING AFFINITIES - It gave rise to new branch of science called Phylogenetic systematics - which gave rise to what is called as “phyloclades” Objectives of Systematics Identification Inventories Evolution Classification Information (RET) Databases Artificial classification Based on easily observable characters such as habit, colour, number or similar features Eg. Sexual system of classification - Linnaeus Natural classification Grouping based on overall similarity of the grouping taxa Started with M. Andanson and culminated in Bentham and Hooker system of classification. Phenetic classification Information is derived from all sources such as morphology, anatomy, embryology, phytochemistry but does not attempt to reflect any evolutionary relationship among the organism. Phylogenetic classification It is based on evolutionary descent of a group of organism and such evolutionary relationship is depicted either through a Phyolgram, Phylogenetic tree or a cladogram. Such evolutionary ancestors can be either monophyletic or paraphyletic. Such an approach is called as Clasdistics and practiced by cladists Evolutionary taxonomic classification It is also an system of classification but accepts leaving out certain descendants of a common ancestor if the gaps are not significant, thus failing to provide a true picture of genealogical history. Such an approach is called eclecticism and practiced by elclecticists.  CLASSIFICIATION Classification is an arrangement of organism into groups on the basis of similarities The groups are in turn assembled into more inclusive groups until all organisms have been assembled into a single most inclusive group. This ranked system of classification is popularly known as Linnaena system SYSTEMA NATURAE Prof. Rudbeck Linnaeus' classification system for plants (I) Public Marriages (Flowers visible to everyone) Monoclinous (Husband and wife have the same bed) [Hermaphrodite flowers: stamens and pistils in the same flower] Without Affinity (Husbands not related to each other) [stamens not united by any of their parts] Without Subordination (All the males of equal rank) [stamens not in set proportion] Monandria - One husband in marriage Diandria - Two husbands in the same marriage Triandria - Three husbands in the same marriage Tetrandria - Four husbands in the same marriage Pentandria - Five husbands in the same marriage Hexandria - Six husbands in the same marriage Heptandria - Seven husbands in the same marriage Octandria - Eight husbands in the same marriage Enneandria - Nine husbands in the same marriage Decandria - Ten husbands in the same marriage Dodecandria - Twelve to nineteen husbands in the same marriage Icosandria - Generally twenty husbands, often more Polyandria - Twenty males or more in the same marriage With Subordination (Some males above the others) [Two stamens always shorter] Didynamia - Four husbands, two taller than the other two Tetradynamia - More than four husbands, two shorter than the others With Affinity (Husbands related to each other) [stamens united with each other or with the pistil] Monadelphia - Husbands, like brothers, arise from one base Diadelphia - Husbands arise from two bases, as if from two mothers Merit: The only merit of this system is the quick and easy identification of plants based on one or a few characteristics. Demerits: 1. The system is not at all sexual in proper sense, but based only on numerical relationship of sex organs. Thus, it can be said that this system was developed on differences rather than on similarities of sex organs. 2. The closely related members go apart and the distantly related members become very close to each other for the numerical relation of the sex organs. 3. The Gymnosperms were placed in the 14th class Didynamia along with Labiatae, an angiosperm family. 4. The Monocotyledons, Dicotyledons and Gymnosperms i.e., phanerogamic plants are not considered separately. Thus, the members of Dicotyledons and Monocoty­ledons become very close, e.g., i. In the 1st class Monandria (flower having 1 stamen) – Globba (Zingiberaceae of Monocotyledons) and Mangifera (Anacardiaceae of Dicotyledons). ii. In the 6th class Hexandria (flowers having 6 stamens) -Alisma (Alismaceae of Monocotyledons) and Rumex (Polygonaceae of Dicoty­- ledons) come very close. Many other examples are also available.  PLANT CLASSIFICATION George Bentham J.D.Hooker Mile stone in understand the classifcation of plants It is was published in 3 volumes (1862 – 1883) It describes 202 families and 7569 genera (97,205 species) MERITS DEMIRTS Great practical value and easy to Does not incorporate phylogeny use for routine identification though it has been published after Widely used for arrangement of Darwin’s theory specimens in herbaria of many Gymnosperms placed between countries monocot and dicots The system is based on careful and Monochlamydeae is unnatural comparative comparison of assemblage which resulted in specimens separation of closely related Gymnosperms separated from families (Eg. Chenopodiaceae and Angiosperms Caryophyllaceae) Placement of ranales in the Liliaceae and Amaryllidaceae beginning of classification separated but many recent systems Dicots are placed before the have merged the families. monocots Unisexuales are close assemblage Description of families and genera of many families with unisexual are precise flower Keys for identification is very useful Creation of ordines anomaly The arrangement is based on Orchidaceae is advanced family natural affinities based on with inferior ovary and zygomorphic morphological characters which is flowers but is placed in the starting easily observable. of monocotyledos. Combination of characters used in Inferior ovary in case of determining the family gamopetalae is placed before but actually is advanced character PLANT CLASSIFICATION Die Natürlichen Pflanzenfamilien (mean “The natural plant families”) 23 volumes during the period 1887- 1915 Engler and Prantl divided plant kingdom into 14 major divisions. They named the 13th division as Embryophyta Siphonogama which included Gymnospermae and Angiospermae MERITS It is a phylogenetic system of classification. Plant groups are arranged mostly according to evolutionary affinities (Primitive groups followed by advanced). The system deals with all groups of plant kingdom – Bacteria, Algae, fungi, Bryophyta, Pteridophyta, Gymnosperms and Angiosperms. The system provides modern taxonomic keys for the identification of each groups of plants. Gymnosperms are treated as separate group. Its position before angiosperm is very accurate and is in perfect accordance to the modern concept of evolution. The position of Asteraceae as last family of dicot is very logical and accurate because it is the highest evolved family in dicots. The position of Orchidacae at the end of Monocots is also very accurate as it is the most evolved family in Monocots. Anatomical data were taken into consideration in this system for the first time. Many large unnatural families of Bentham and Hooker have been split into smaller and natural families for eg. Moraceae was split into Ulmaceae and Moraceae. Aboltion of Monochlamydeae has resulted in bringing together several closely related families. The terms cohort and natural order have been replaced by the appropriate terms order and family, respectively. Closely related families Liliaceae and Amaryllidaceae have been brought under the same order Liliiflorae. DEMERITS Monocotyledons are considered primitive and placed before Dicotyledons which is not correct according to modern evolutionary evidences. Amentiferae with families as Betulaceae, Juglandaceae and Fagaceae with reduced unisexual flowers, having few floral members and borne in catkins, were considered primitive. It has been established from studies on wood anatomy, palynology and floral anatomy that Amentiferae is advanced group. The simplicity of flowers is due to evolutionary reduction and not primitiveness. Dichlamydeous forms (distinct calyx and corolla) were considered to have evolved from the monochlamydeous forms (single whorl of perianth). This view is not tenable. Derivation of free central placentation from the parietal placentation, and of the latter from axile placentation is contrary to the evidence from floral anatomy. Free central placentation is now believed to have evolved from axile placentation through the disappearance of septa. Ranales are now considered as a primitive group with bisexual flowers, spirally arranged floral parts and numerous floral members. In this classification, these are considered to be advanced.. Family Liliaceae of Engler and Prantl is a large unnatural assemblage, which has been split into several smaller monophyletic families like Liliaceae, Alliaceae, Asphodelaceae in the recent classification of Judd et al. (2002), APG II (2003) and Thorne (2003). International code for Botanical Nomenclature NEED FOR A SCIENTIFIC NAME 1. Vernacular names are not available for all the species known to man. 2. Vernacular names are restricted and are applicable in a single or few languages only. They are not universal in their application. 3. In case of widely distributed plants, many common names may exist for the same species in different localities which may cause confusion.  BINOMIAL NOMENCLATURE Solanum caule inermi herbaceo, foliis pinnatis incisis 'solanum with the smooth stem which is herbaceous and has incised pinnate leaves.‘ Lycopersicon esculentum Mill Carolus Linnaeus – Species plantarum (1753) According to this system the scientific name of a plant consists of two Latinized words followed by authority 1. Generic name or Generic epithet 2. Species name of specific epithet 3. Authority  BOTANICAL NOMENCLATURE GOVERNING BODY International code of Botanical nomenclature (ICBN) published by the International Association of Plant Taxonomy (IAPT). WHAT DO THEY DO 1. Rules and recommendations dealing with the formal botanical names that are given to plants. 2. Its intent is that each taxonomic group ("taxon", plural "taxa") of plants has only one correct name that is accepted worldwide. Rochester Code (1892) Concept of type was introduced Tautonym was given up Linnaeus species plantarum was taken as starting point of nomenclature. (1st June, 1973) Latin diagnosis was made compulsory Nomina Generic and species conservanda American code in 1907 13 codes – every once in six years.  WHY LATIN ? It is also mandatory to have Latin diagnosis for any new taxon published from 1 January 1935 onwards. 1. Latin is dead language and meanings and interpretation are not subject to changes unlike English and other languages. 2. Latin is specific and exact in the meaning 3. Grammatical sense of the word is commonly obvious (white translated as album – neuter, alba – femine or albus – masculine) 4. Latin language employs the Roman alphabet which fits well in the text of most languages. Veinna Code (2006): It has three divisions and appendices 1. Principles 2. Rules and Recommendations 3. Provisions for governance of code Principles of ICBN The philosophical basis of code is formed by the following six principles 4. Botanical nomenclature is independent of zoological nomenclature. 5. The application of names of taxonomic groups is determined by means of nomenclature types (Typification) 6. The nomenclature of taxonomic groups is based upon priority of publication. 7. Each taxonomic group with a particular circumscription, position, and rank can bear only one correct name, the earliest that is in accordance with the rules, except in specific cases. Botanical & Zoological Codes are Separate Ficus caricus Ficus ficus Cecropia Cecropia Botanical & Zoological Codes are Separate Iris versicolor Iris oratoria Culcita coniifolia Culcita novaeguineae (echinoderm)  TYPIFICATION (Articles 7 -10) ( Not before 1958) A species is described with reference to one and only one type specimen deposited in a herbarium The function of types is strictly nomenclatural, anchors the name Does not have to be “typical” or representative of the species 1. Holotype 2. Isotype 3. Syntype 4. Paratype 5. Lectotype 6. Neotype 7. Epitype 8. Topotype TYPIFICATION (Articles 7 -10) ( Not before 1958) Paratype: A paratype is a specimen cited with original description other than the holotype or isotype. (Two seasonal collection). Syntype: When author fails to designate a Holotype During revisionary work - 2 or multiple specimens are cited, then one specimen is chosen to be the Lectotype: When holotype is missing then one of original specimen from isotype is chosen to serve as holotype. Neotype: When neither the illustration nor the any one of either the holo, syn, para etc. does not exist then a revisionary person can select one specimen which fits the best of description and designate it as neotype Epitype: Ambguity – The specimen desiginated either as holo…etc is demonstrably ambiguous and cannot be critically identified for the precise application of the name of taxon – An illustration of a specimen can serve as a type. 3 Principle The nomenclature of taxonomic groups is based upon priority of publication. SUPERFLUOUS NAME Vallisineria natans (Lour.) Hara, 1974; Physkium natans Lour. 1790. (Basionym); Vallisineria physkium 1826 (nomen. Superfl.). TAUTONYMS Malus malus (Linn.) Britt. 1888 Pyrus malus L. 1753 Malus pumilla Mill. 1768 NOMEN NUDUM ( nom.nud): A name with no accompanying description Quercus dilatata Wall. 1836. Quercus himalayana Bhadur. 1972  EFFECTIVE AND VALID PUBLICATION Effective publication 1. Priority of publication starts with Linnaeus Species Plantarum – 1 st May 1753 and applies to rank of family and below. 2. Scientific journal, detailed illustration, detailed description, indication of a type, latin diagnosis for diagnostic characters. 3. Publication in newspapers. Catalogues (1st January, 1953 – Salvia oxyodon 1850. The journal of international conifer preservation society), Seed exchange lists (1st January, 1977) is not valid publication. 4. Species nova (Sp. nov.): Tragopogon kashmirianus G. Sing sp. nov. (1976) This are rules for first publication, in successive publications it would appear as Tragopogon kasmirianus G.Sing, Forest flora Srinagar p.123. f.4. 1976 not simply as Tragopogn kasmirianus. 4. Combination nova (Comb. nov.): Vallisenaria natans (Lour) Hara comb. nov. (1974) Basionymn Physkium natans Lour. 1790  LIMITATIONS TO THE PRINCIPLE OF PRIORITY 1. Starting dates: Angiosperms, algae, slimemould (1.5.1753); Mosses (1.1.1801); Fossils (31.12.1820) 2. Note above Family Rank: The principle of priority is applicable only up to the family rank and not above. 3. Not outside the Rank: When choosing a correct name for a taxon, names or epithets available at that rank should be considered. For eg. When Magnolia grandiflora var. foetida L. 1753 was raised to specific rank it was called Magnolia grandiflora L. 1759 and not M.foetida 4. Nomina Conservanda : Strict application of the principle of priority has resulted in numerous changes, but such name changes were not accepted by many persons For eg. Triticum sativum L. and T.hybernum L. (1753) (Fiori and Paoletti – selected T.sativum as correct name in the year 1896. but in 1980 Kerg pointed that Merat in 1821 had selected T.hybernum as the correct Family names End in –aceae, but note the following eight conserved names (alternative old names allowed by the Code): Asteraceae Compositae Hypericaceae Gutifferae Brassicaceae Cruciferae Apiaceae Umbelliferae Arecaceae Palmae Lamiaceae Labiatae Fabaceae Leguminosae Poaceae Graminae Scientific names of taxonomic groups are treated as Latin regardless of their derivation. Commemoration of a person: Victoria, Vanda hookeranum Based on place: Arabis, Hedera nepalensis Based on character – Zanthoxylum ( Yellow wood, Hygrophila), Chenopodium album Aborginal names: Narcissus ( Greek name for Daffodils), Ginkgo (Chinese name) BIOMETRICS AND METHODOLOGY OF CLADISTICS Classification based on different criteria and employs a distinct methodology It uses data to establish relationship between organisms in two Phenetic method Phylogenetic method Basically uses genealogical methods.Basically uses morphological characters Numerical taxonomy received great importance with the advancement of computers – Mathematical taxonomy, taxometrics, taximetrics, multivariate morphometrics etc. Contributors : Sneath – 1957, Michener and Sokal, - 1958. Cultimated in publication of book Principles of Numercial taxonomy - 1963 Numerical taxonomy is grouping of taxa based on numerical methods of taxonomic units into taxa on basis of their character states. Principles of Numerical Taxonomy The greater the content of information in the taxa of a classification and the more characters its is based upon , the better the given classification will be. A priori every character is of equal weight in creating natural taxa Overall similarity between any two entities is function of their individual similarities in each of the many characters in which are being compared. Distinct taxa can be recognised because correlations of characters differ in groups of organism under study Phylogenetic inferences can be made from the taxonomic structures of a group and also from character co- relations, given certain assumptions about evolutionary pathways and mechanism Taxonomy is viewed and practiced as empirical science. Classifications are based on phenetic similarity. OPERATIONAL TAXONOMIC UNITS (OTUS) Any sample, item, which is selected / used for analysis is called OTUs Basic unit of numerical taxonomy May be individual species, genus, family , order, class etc. In case of OTUs is above the individual then adequate relation relationship of various forms becomes individual eg. When genera is OTU then it should be represented by different species. METHODS AND PROCEDURE OF NUMERICAL TAXONOMY Selection of taxa (OTUs) Selection of characters or traits Cluster analysis via computer software Determination of taxonomic relationship between OTUs SELECTION Classification on the OF basis RULES of overall FOR SELECTION OF UNIT similarities. CHARACTERS CHARACTERS 1) Binary character: A Included all part of the organism character having only two Not less than 50 characters state as present or absent Belong to all stage of life cycle 2) Multistate character: A Due attention given to morphology, character having three or physiology, ecology and distribution more different states and etc. may be qualitative or quantitative. CHARACTER WEIGHTING Equal Weighting: All the characters selected are given equal weightage while creating taxonomic groups and is one of the principle of numerical taxonomy Successive weighting: The characters which showIn the lease homoplasy unique are identified and given more weightage in the CLUSTER ANALYSIS subsequent analysis. In this computer sorts out the OTUs according to the overall similarity i.e. according to the number of character in common. The software produced a phenogram that is a dendrogram (branch tree diagram) which shows the taxonomic relationship between the taxa. A C B E A C D B E  A C D B E Distance method – An arthematic approach F UNWEIGHTED PAIR GROUP METHOD WITH ARITHMETIC MEAN (UPGMA) UNDERSTANDING THE PHYLOGENETIC TREE  PLEISOMORPHIC (PRIMITIVE) AND APOMORPHIC (ADVANCED) CHARACTERS DOCTTRINE OF RECAPTIULATION: It holds that early phases in development are supposed to exhibit primitive features. Ontogeny repeats phylogeny DOCTTRINE OF TERATOLOGY: Teratology or abnormality is reminiscent of some remote ancestor DOCTTRINE OF SEQUENCES: Organisms are arranged in series, with two ends, the one end being pleisomorphic and other end being apomorphic DOCTTRINE OF ASSOCIATION: One structure has evolved from another – Vessels from tracheids DOCTTRINE OF COMMON GROUND PLAN: Characters common to all members of a group must have been possessed by original ancestor and therefore be primitive DOCTTRINE OF CHARACTER CORRELATION: Cladistics methods DOCTTRINE OF CONSERVATIVE REGIONS: Certain regions of plant have been less susceptible to environmental influences Pleisomorphic : Primitive unchanged from ancestral / unspecialised character Symplesiomorphic character: Primitive / Shared ancestral character (Sym means Apomorphic: Derived/ Specialised shared character) character/trait found in the descendent that is different from the ancestor. Synapomorphic character: Trait Autapomorphic: Derived is shared by two or more taxon characters that is unique to a and their most common ancestor taxon. whose ancestor does not possess. Homoplasy : A character is similar (or present) in two taxa because of independent evolutionary origin (i.e. similarity does not derive from common ancestory) Understanding evolution Monophyletic: descendents of common ancestor Paraphyletic: Includes some but not all of the descendant of common ancestor (eft out ancestor) Polyphyletic: members donot share a common Concept recent ancestor of Sister(more Taxa than one common ancestor)  Chloroplast cpDNA– smallest – 120 – 160 Kilo base pairs Mitochondrian – 200 – 2500 kbp - MATERNAL Nucleus – millions and millions atpB – ATPase betasub unit gene – Chloroplast DNA – highly 1450 base pairs conserved, Closed circular rbCL – Ribulose 5 – biphosphate molecule – with 2 genes that Carboxylase/oxygenase (Rubisco) encode for same genes in Central to global carbon cycle, opposite directions known as universal, 1428 baes pairs inverted repeats 18srRNA - 1855 base pairs matK- Gene encoding Mutrase enzyme invovlded in Splicing of introns & Also atpB rpL16 – noncoding region mainly used in construction of phylogenetic tree in Grasses 4734 Base Nuclear – ITS region involved in NOW ALMOST 18 pairs coding of larger subunit of different genes are Ribosome used construction of phylogenetic tree