Angiosperm phylogeny grouping I (APG I)
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The Angiosperm Phylogenetic Group (APG) was established in the late 1990s to create a phylogenetic-based classification system for angiosperms, which are seed-producing flowering plants. APG I, published in 1998, recognized 462 families grouped into 40 monophyletic orders, rejecting previous classification systems that did not accurately reflect evolutionary relationships. Subsequent updates, APG II and APG III, further refined this classification, influencing major herbaria and botanical references worldwide.
Angiosperm phylogeny grouping I (APG I)
- 1. Angiosperm Phylogeny Group I (APG I) PABASARA GUNAWARDANE
- 2. Angiosperms •The botanical term "Angiosperm", from the Ancient Greek •The flowering plants •Also known as Magnoliophyta •The most diverse group of land plants •Seed-producing plants •Flowers, endosperm within the seeds, and the production of fruits that contain the seed are the distinguished features
- 4. History of Angiosperm Classification •Artificial System: On the basis of one or few characters of plants •Natural system: A large number of morphological characters were taken into consideration, in the natural systems of classification •Phylogenetic system: Based on evolutionary sequence as well as genetic relationships among different groups of plants
- 5. Angiosperm Classification •In the past, classification systems were typically produced by an individual botanist or by a small group •The result was a large number of systems • Different systems and their updates were generally favored in different countries
- 6. Bentham & Hooker System
- 7. Engler System Adolf Engler (1844–1930)
- 10. •Before the availability of genetic evidences, angiosperms were classified using their morphology and biochemistry •After the 1980’s genetic evidences were available and phylogenetic methods came into action
- 11. Angiosperm Phylogeny Group •In the late 1990s, an informal group of researchers from major institutions worldwide came together •Established APG •Objective was to provide a widely accepted and more stable point of reference for angiosperm classification •APG I was published in 1998 as their first attempt in Annals of the Missouri Botanical Garden
- 13. Angiosperm Phylogeny Group •The initial 1998 paper by the APG made angiosperms the first large group of organisms to be systematically re- classified primarily on the basis of genetic characteristics •Emphasized the need for a classification system for angiosperms at the level of families, orders and above • Existed systems are rejected is because they are not phylogenetic
- 14. Angiosperm Phylogeny Group •The group published 462 families of angiosperms grouped into 40 monophyletic orders Monophyletic: Consists of an ancestral species and all its descendants
- 15. •The outline of a phylogenetic tree of all flowering plants became established •Several well supported major clades* involving many families of flowering plants were identified •the new knowledge of phylogeny revealed relationships in conflict with the then widely used modern classifications • It became clear that none of the previous classifications accurately reflected phylogenetic relationships of flowering plants * A clade is a group of organisms that consists of a common ancestor and all its lineal descendants
- 16. Principles of the APG system •The Linnean system of orders and families should be retained •Groups should be monophyletic (Consist of all descendants of a common ancestor) •A broad approach is taken to defining the limits of groups such as orders and families •Above or parallel to the level of orders and families, the term clades is used more freely
- 17. Features of APG •Formal, scientific names are not used above the level of order, named clades being used instead •A substantial number of taxa whose classification had traditionally been uncertain are given places •Alternative classifications are provided for some groups •A major outcome of the classification is the disappearance of the traditional division of the flowering plants into two groups, monocots and dicots (The monocots are recognized as a clade, but the dicots are not)
- 19. Why Dicots became Eudicots?? • The angiospermous plants were divided into two distinct classes: the monocotyledons or Monocotyledoneae, and the dicotyledons or Dicotyledoneae • The two cotyledons descriptive of the traditional classification ‘dicots’ also occur in the Coniferales, Cycadales, and Gnetales (Judd and Olmstead 2004) and is now thought as an ancestral feature of the flowering plants and not distinct to any group within.
- 20. • The genetic approach is more modern, precise and objective • The system is a group-work • Use of monophyletic groups (i.e. groups which consist of all descendants of a common ancestor) provides a descriptive link between the groups • A substantial number of taxa whose classification had traditionally been uncertain are given places Advantages of APG
- 21. • Named clades being used instead of Formal, scientific names above the level of order. thus, eudicots and monocots are not given a formal rank • Taxa which were uncertain to rank were ranked but 25 families are still remain uncertain position • Alternative classifications are provided for some groups (e.g. the Fumariaceae can either be treated as a separate family or as part of Papaveraceae) • What came first and what came after is not clearly determined Disadvantages of APG
- 22. • APG II (2003) and APG III (2009) has been introduced and updated APG I Updating APG
- 23. • A significant number of major herbaria, including Kew, are changing the order of their collections in accordance with APG • The influential World Checklist of Selected Plant Families (also from Kew) is being updated to the APG III system • In the USA, a recent photographic survey of the plants of the USA and Canada is organized according to the APG II system. • In the UK, the latest edition of the standard flora of the British Isles is based on the APG III system Influence of APG
- 24. • The Angiosperm Phylogeny Group (1998) An ordinal classification for the family of flowering plants Annals of the Missouri Botanical Garden Vol. 85, No. 4 (1998), pp. 531-553 • Angiosperm Phylogeny Group II (2003), An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II (PDF), Botanical Journal of the Linnean Society 141: 399–436 • Ben G. Bareja (2012) Monocots, Dicots and Eudicots Distinguished. Available at: http://www.cropsreview.com/monocots.html (Accessed 22 September 2015) • Michal Yakir (2013) Which Phylogenic systematics should be used. Available at: http://www.michal- yakir.de/cronquist-apg-1.html (Accessed 22 September 2015) • Ho Dinh Hai (2012) APG Systems of Plant Classification. Available at: http://www.edibleplantsinvietnam.com/apg-systems-of-plant-classification.html (Accessed 22 September 2015) References
Editor's Notes
- #4: The ancestors of flowering plants diverged from gymnosperms around 245–202 million years ago, and the first flowering plants known to exist are from 160 million years ago. They diversified enormously during the Lower Cretaceous and became widespread around 120 million years ago, but replaced conifers as the dominant trees only around 60–100 million years ago.
- #5: Based on different criteria, many systems of classification of plants have been proposed by various philosophers, herbalists and botanists Artificial System: Theophrastus, Albertus Magnus, Carl Linnaeus(created a sexual system of classification) Natural system: George Bentham (1800-1884) and Sir Joseph D. Hooker Phylogenetic system: Concepts of natural selection and lineage relationships present in Origin of Species is the base.
- #7: A natural system. 202 families. Gymnosperms were kept between monocots and dicots. The most important natural system of classification of seed plants. recognized 97,205 species belonging to 7,569 genera of families of flowering plants.
- #8: A phylogenetic system. Gymnosperms are more primitive to angiosperms. 280 families. believed that classification systems should reflect evolutionary history. developed first phylogenetic system of plant classification (at Botanical Garden in Berlin) and that gave a slightly changed August Wilhelm Eichler system. Families and orders arranged based on the complexity of floral morphology
- #10: Cronquist system is a taxonomic classification system of flowering plants. The 'Cronquist System' of Flowering Plant (Magnoliophyta) classification groups flowering plants into two classes Magnoliopsida (dicotyledons) and Liliopsida (monocotyledons) with related Orders (groups of families) placed in Subclasses.
- #11: while confirmed or clarified some relationships in existing classification systems, it radically changed others. This genetic evidence created a rapid increase in knowledge that led to many proposed changes; stability was "rudely shattered". This posed problems for all users of classification systems
- #12: Authors: Bremer, K., M. W. Chase, P. F. Stevens, A. A. Anderberg, A. Backlund, B. Bremer, B. G. Briggs, P. Endress, M. F. Fay, P. Goldblatt, M. H. G. Gustafsson, S. B. Hoot, W. S, Judd, M. Källersjö, E. A. Kellogg, K. A. Kron, D. H. Les, C. M. Morton, D. L. Nickrent, R. G. Olmstead, R. A. Price, C. J.. Quinn, J. E. Rodman, P. J. Rudall, V. Savolainen, D. E. Soltis, P. S. Soltis , K. J. Sytsma and M. Thulin
- #16: (e.g. Cronquist, 1981; Thorne, 1992; Takhtajan, 1997), which were based on selected similarities and differences in morphology rather than cladistic analysis of larger data sets involving DNA sequences or other forms of systematic data
- #17: "The family is central in flowering plant systematics." An ordinal classification of families is proposed as a "reference tool of broad utility". Orders are considered to be of particular value in teaching and in studying family relationships The main reason why existing systems are rejected is because they do not have this property, they are not phylogenetic. Thus of orders, it is said that a limited number of larger orders will be more useful. Families containing only a single genus and orders containing only a single family are avoided where this is possible without violating the over-riding requirement for monophyly. The authors say that it is "not possible, nor is it desirable" to name all clades in a phylogenetic tree; however, systematists need to agree on names for some clades, particularly orders and families, to facilitate communication and discussion.
- #18: in which a number of families can either be regarded as separate or can be merged into a single larger family. For example, the Fumariaceae can either be treated as a separate family or as part of Papaveraceae