Consortium for Educational Communication

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1 Consortium for Educational Communication Module on TITLE: SALIENT FEATURES OF CLASSIFICATION SYSTEM BY ANGIOSPERM PHYLOIGENY GROUP (APG) By Mr. Anzar A. Khuroo Assistant Professor Department of Botany University of Kashmir

TEXT (I) Introduction Classification is a basic human activity. The ability to classify different entities is a characteristic inherent in all of us.

Most of us arrange the living and non-living objects into different groups. Thus, classification is the placement of objects/ organisms into groups for their effective organization.

Historically, plant classification systems have been largely proposed by either an individual taxonomist, or a group of a few taxonomists.

2 TEXT (I) Introduction Classification is a basic human activity. The ability to classify different entities is a characteristic inherent in all of us. For instance, we humans taste food and then classify it as good, bad or inedible; or we smell a flower and then classify it as pleasant, offensive, odorless. Most of us arrange the living and non-living objects into different groups. Thus, classification is the placement of objects/ organisms into groups for their effective organization. In the same sense, the plant classification is the arrangement of plants into groups of some type of ordered system. Historically, plant classification systems have been largely proposed by either an individual taxonomist, or a group of a few taxonomists. Consequently, no single system of plant classification has been followed all across the world. In fact, from time to time, a large number of classification systems have been proposed by different plant taxonomists. These different systems of classification are followed in different parts of the world. For example, the Engler & Prantl system of classification is followed in the continental Europe, Bentham & Hooker s system in Britain and erstwhile British colonies, Takhtajan s system in the former USSR, whereas Cronquist s system is followed in the Americas. Before the availability of molecular evidences (particularly DNA characters) during recent decades, the classification of angiosperms (also known as flowering plants, and the largest group of plants) was mostly based on their gross morphology, preferably flower morphology, and anatomy. However, during the last 3 decades, increasing availability of molecular evidences, and their analysis by phylogenetic methods, confirmed several

3 already known evolutionary relationships of angiosperms in the existing classification systems, but in many cases proposed a radical change. Due to this rapid increase in molecular evidence that led to many proposed changes, stability of the previous classifications was altogether lost, which posed problems for all users of angiosperm classification systems. Faced with these problems, in the late 1990s, an informal consortium of taxonomists from renowned institutions worldwide came together under the name of the Angiosperm Phylogeny Group or APG. Their intention was to provide a widely accepted and more stable angiosperm classification. Their first attempt at a new system of classification was published in 1998 (known as the APG-I). As of now, two revisions have been published in 2003 (APG II) and in 2009 (APG III), each superseding the previous system. Eight taxonomists have been listed as authors for the APG classification, namely: Birgitta Bremer (Swedish Academy of Sciences), Kåre Bremer (Uppsala University), Mark W. Chase (Royal Botanic Gardens, Kew), Michael F. Fay (Royal Botanic Gardens, Kew), James L. Reveal (University of Maryland), Douglas E. Soltis (University of Florida), Pamela S. Soltis (Florida Museum of Natural History), Peter F. Stevens (University of Missouri). In addition to these 8 lead authors, 33 taxonomists are listed as contributors. The APG system of classification is mainly based on the synthesis of knowledge, from morphological to molecular data, about the relationships of angiosperm using phylogenetic methods. The main hypothesis behind the development of APG system of classification has been that all the previous angiosperm classification systems were not based on assembling the monophyletic groups (i.e. groups that include all the

4 descendants of a common ancestor). Increasingly, the APG system of classification is becoming popular, with a number of major herbaria rearranging their collections to match the latest APG classification system. (II) Principles of the APG classification Only the monophyletic groups (e.g. order, family) should be recognized, i.e. consisting of all the descendants of a common ancestor. The main reason for the previous classification systems to be avoided is that they are not monophyletic. The Linnaean system of orders and families should be retained. The family is central in the angiosperm taxonomy, and the orders are of particular value in teaching and in studying family relationships; therefore, an ordinal classification of families is proposed as a reference tool of broad utility. A broad approach is taken in defining the limits of groups, such as orders and families. Thus, a limited number of larger orders will be more useful, e.g. 60 orders in the APG III. Wherever possible, families with a single genus and orders with a single family should be avoided, but without violating the main rule of monophyly. Above the level of orders, the term clade is used more (III) frequently. Although some clades have been given formal names, still it is neither possible nor desirable to name all the clades in a phylogenetic tree. However, taxonomists need to agree on names for some clades, particularly orders and families, to facilitate communication. An outline of APG-III classification system A number of informal groups (i.e. clades) have been

5 recognised, in which 56 orders are distributed in the latest version of APG-III classification system. These clades include: (1) MAGNOLIIDS (2) MONOCOTS (3) COMMELINIDS (4) EUDICOTS (5) CORE EUDICOTS (6) PENTAPETALAE (7) FABID/ROSID-I (8) N-FIXING CLADE (9) MALVID/ROSID-II (10) ASTERIDS (11) LAMIID/ASTERID-I (12) CAMPANULID/ASTERID-II Besides these informal clades and orders therein, 4 orders (Amborellales, Nymphaeales, Austrobaileyales, Chloranthales) have been placed at the start of the classification without any informal clade name. In the APG-III, a few families, namely: Dasypogonaceae, Metteniusaceae, Oncothecaceae, Icacinaceae, Boraginaceae, Vahliaceae, are still unplaced. An outline of the linear sequence of orders along with the inclusive families in the latest version of APG-III classification system is as follows: 1. Amborellales Amborellaceae 2. Nymphaeales - [Hydatellaceae [Cabombaceae + Nymphaeaceae]] 3. Austrobaileyales - [Austrobaileyaceae [Trimeniaceae + Schisandraceae]] 4. Chloranthales - Chloranthaceae MAGNOLIIDS

6 5. Magnoliales - [Myristicaceae [Magnoliaceae [[Himantandraceae + Degeneriaceae] [Eupomatiaceae + Annonaceae]]]] 6. Laurales - [Calycanthaceae [[Siparunaceae [Gomortegaceae + Atherospermataceae]] [Monimiaceae [Hernandiaceae + Lauraceae]]]] 7. Canellales - [Canellaceae + Winteraceae] 8. Piperales - [[Hydnoraceae + Aristolochiaceae] [Piperaceae + Saururaceae]] MONOCOTS 9. Acorales Acoraceae 10. Alismatales - [Araceae [Tofieldiaceae [[Alismataceae [Hydrocharitaceae + Butomaceae]] [Scheuchzeriaceae [Aponogetonaceae [Juncaginaceae [Maundiaceae [[Posidoniaceae [Ruppiaceae + Cymodoceaceae]] [Zosteraceae + Potamogetonaceae]]]]]]]]] 11. Petrosaviales Petrosaviaceae 12. Dioscoreales - [Nartheciaceae [[Taccaceae + Thismiaceae] [Burmanniaceae + Dioscoreaceae]]] 13. Pandanales - [Velloziaceae, Triuridaceae, Stemonaceae, [Pandanaceae + Cyclanthaceae]] 14. Liliales - [Corsiaceae [Campynemataceae [Petermanniaceae [Colchicaceae + Alstroemeriaceae]], Melanthiaceae, [[Philesiaceae + Rhipogonaceae] [Smilacaceae + Liliaceae]]]] 15. Asparagales - [Orchidaceae [[OrchidaceaeBoryaceae [Blandfordiaceae [Lanariaceae [Asteliaceae + Hypoxidaceae]]]] [[Ixioliriaceae + Tecophilaeaceae] [Doryanthaceae [Iridaceae [Xeronemataceae [Xanthorrhoeaceae [Amaryllidaceae + Asparagaceae]]]]]]]] COMMELINIDS

7 Unplaced - Dasypogonaceae 16. Arecales Arecaceae 17. Poales - [[Typhaceae + Bromeliaceae] [Rapateaceae [[Mayacaceae [Eriocaulaceae + Xyridaceae]] [Thurniaceae [Juncaceae + Cyperaceae]]] [[Anarthriaceae [Centrolepidaceae + Restionaceae]] [Ecdeiocoleaceae + Poaceae [Flagellariaceae + Joinvilleaceae]]]]]]]] 18. Commelinales - [[Commelinaceae + Hanguanaceae] [Philydraceae [Haemodoraceae + Pontederiaceae]]] 19. Zingiberales - [Musaceae, [Strelitziaceae + Lowiaceae], Heliconiaceae, [[Cannaceae + Marantaceae] [Costaceae +Zingiberaceae]] 20. Ceratophyllales - Ceratophyllaceae EUDICOTS 21. Ranunculales - [Eupteleaceae [Papaveraceae [[Lardizabalaceae + Circaeasteraceae] [Menispermaceae [Berberidaceae + Ranunculaceae]]]]] 22. Proteales - [Sabiaceae [Nelumbonaceae [Platanaceae + Proteaceae]]] 23. Trochodendrales Trochodendraceae 24. Buxales - [Didymelaceae + Buxaceae] CORE EUDICOTS 25. Gunnerales - [Gunneraceae + Myrothamnaceae] PENTAPETALAE 26. Dilleniales Dilleniaceae 27. Saxifragales - [Peridiscaceae [[Paeoniaceae [Altingiaceae [Hamamelidaceae [Cercidiphyllaceae + Daphniphyllaceae]]]] [[Crassulaceae [Aphanopetalaceae [Tetracarpaeaceae [Penthoraceae + Haloragaceae]]]] [Iteaceae [Grossulariaceae + Saxifragaceae]]]]], Cynomoriaceae unplaced

8 28. Vitales - Vitaceae ROSIDS FABID/ROSID I 29. Zygophyllales - [Krameriaceae + Zygophyllaceae] 30. Celastrales - [Lepidobotryaceae + Celastraceae] 31. Oxalidales - [Huaceae [[Connaraceae + Oxalidaceae] [Cunoniaceae [Elaeocarpaceae [Brunelliaceae + Cephalotaceae]]]]] 32. Malpighiales - [[Achariaceae [Goupiaceae + Violaceae] [Passifloraceae [Lacistemataceae + Salicaceae]]]], [Lophopyxidaceae, Putranjivaceae], Humiriaceae, [Ctenolophonaceae [Erythroxylaceae + Rhizophoraceae]], Irvingiaceae, Pandaceae, Ochnaceae, [[Bonnetiaceae + Clusiaceae] [Calophyllaceae [Hypericaceae + Podostemaceae]]], Centroplacaceae, [Elatinaceae + Malpighiaceae], [Balanopaceae [[Trigoniaceae + Dichapetalaceae] [Chrysobalanaceae + Euphroniaceae]]], Caryocaraceae, [Peraceae [Rafflesiaceae + Euphorbiaceae]], [Phyllanthaceae + Picrodendraceae], Linaceae, Ixonanthaceae N-FIXING CLADE 33. Fabales - [Quillajaceae [Fabaceae [Polygalaceae + Surianaceae]]] 34. Rosales - [Rosaceae [[Rhamnaceae [Elaeagnaceae [Barbeyaceae + Dirachmaceae]]] [Ulmaceae [Cannabaceae [Moraceae + RosaceaeUrticaceae]]]]] 35. Cucurbitales - [Anisophylleaceae [[Corynocarpaceae + Coriariaceae] [Cucurbitaceae [Tetramelaceae [Datiscaceae + Begoniaceae]]]], Apodanthaceae unplaced 36. Fagales - [Nothofagaceae [Fagaceae [[Myricaceae + Juglandaceae] [Casuarinaceae [Ticodendraceae +

9 Betulaceae]]]]] MALVID/ROSID II 37. Geraniales - [Geraniaceae [[Melianthaceae + Francoaceae] [Vivianaceae + Ledocarpaceae]]] 38. Myrtales - [Combretaceae [[Onagraceae + Lythraceae] [[Vochysiaceae + Myrtaceae] [Melastomataceae [Crypteroniaceae [Alzateaceae + Penaeaceae]]]]]] 39. Crossosomatales - [[Staphyleaceae [Guamatelaceae [Crossosomataceae + Stachyuraceae]]] [Aphloiaceae [Geissolomataceae + Strasburgeriaceae]]] 40. Picramniales Picramniaceae 41. Sapindales - [Biebersteiniaceae, Nitrariaceae, [[Kirkiaceae [Anacardiaceae + Burseraceae]] [Sapindaceae [Simaroubaceae, Rutaceae, Meliaceae]]]] 42. Huerteales - [[Gerrardinaceae + Petenaeaceae] [Tapisciaceae + Dipentodontaceae]] 43. Malvales - [Neuradaceae [Thymelaeaceae [Sphaerosepalaceae, Bixaceae, [Cistaceae [Sarcolaenaceae + Dipterocarpaceae]], [Cytinaceae + Muntingiaceae], Malvaceae]] 44. Brassicales - [[Akaniaceae + Tropaeolaceae] [[Moringaceae + Caricaceae] Setchellanthaceae[ [Limnanthaceae [Koeberliniaceae[ [Bataceae + Salvadoraceae]] [Emblingiaceae [Pentadiplandraceae [Gyrostemonaceae, Resedaceae, Stixis and relatives] Tovariaceae [Capparaceae [Cleomaceae + Brassicaceae]]]]]]]]] 45. Berberidopsidales - [Aextoxicaceae + Berberidopsidaceae] 46. Santalales - [Erythropalaceae [Strombosiaceae [Coulaceae [Ximeniaceae, Aptandraceae, Olacaceae

10 [Octonemaceae [[Loranthaceae [Misodendraceae + Schoepfiaceae]] [Opiliaceae + Santalaceae]]]]]]], Balanophoraceae unplaced 47. Caryophyllales - [[[Droseraceae [Nepenthaceae [Drosophyllaceae [Ancistrocladaceae + Dioncophylleaceae]]]] [[DroseraceaeFrankeniaceae + Tamaricaceae] [Polygonaceae + Plumbaginaceae]]] [Rhabdodendraceae [Simmondsiaceae [[Asteropeiaceae + Physenaceae] [Macarthuria [Microteaceae [[Caryophyllaceae [Achatocarpaceae + Amaranthaceae]] [Stegnospermataceae [Limeaceae [[Lophiocarpaceae [Hypertelis [Barbeuiaceae [Aizoaceae [Gisekiaceae [Sarcobataceae, Phytolaccaceae, Nyctaginaceae]]]]]] [Molluginaceae [Montiaceae [[Halophytaceae [Didiereaceae + Basellaceae]] [Talinaceae [Anacampserotaceae [Portulacaceae + Cactaceae]]]]]]]]]]]]]]]] ASTERIDS 48. Cornales - [[Cornaceae [Grubbiaceae + Curtisiaceae]] [Nyssaceae [Hydrostachyaceae [Hydrangeaceae + Loasaceae]]]] 49. Ericales - [[Balsaminaceae [Marcgraviaceae + Tetrameristaceae]] [[Polemoniaceae + Fouquieraceae], Lecythidaceae, [[Sladeniaceae + Pentaphylacaceae], [Sapotaceae [Ebenaceae[ + Primulaceae]], [Mitrastemonaceae, Theaceae, [Symplocaceae [Styracaceae + Diapensiaceae]], [[Sarraceniaceae [Roridulaceae + Actinidiaceae] [Clethraceae [Cyrillaceae + Ericaceae]]]]]]] LAMIID/ASTERID I Unplaced - [Metteniusaceae, Oncothecaceae], Icacinaceae 50. Garryales - [Garryaceae + Eucommiaceae] Unplaced - Boraginaceae, Vahliaceae

11 51. Gentianales - [Rubiaceae [Gentianaceae [Loganiaceae [Gelsemiaceae + Apocynaceae]]]] 52. Lamiales - [Plocospermataceae [[Carlemanniaceae + Oleaceae] [Tetrachondraceae [Peltanthera, [Calceolariaceae + Gesneriaceae], [Plantaginaceae [Scrophulariaceae [Byblidaceae, Linderniaceae [Stilbaceae [[Lamiaceae [Mazus etc. [Phrymaceae [Paulowniaceae + Orobanchaceae]]]] [Thomandersiaceae, Verbenaceae, Pedaliaceae, [Schlegeliaceae + Martyniaceae] Bignoniaceae, Acanthaceae, Lentibulariaceae]]]]]] 53. Solanales - [[Montiniaceae [Sphenocleaceae + Hydroleaceae]] [Convolvulaceae + Solanaceae]] CAMPANULID/ASTERID II 54. Aquifoliales - [[Cardiopteridaceae + Stemonuraceae] [Aquifoliaceae [Helwingiaceae + Phyllonomaceae]]] 55. Asterales - [[Rousseaceae + Campanulaceae] [Pentaphragmataceae [[Alseuosmiaceae [Phellinaceae + Argophyllaceae]] [Stylidiaceae [Menyanthaceae [Goodeniaceae [Calyceraceae + Asteraceae]]]]]]] 56. Escalloniales Escalloniaceae 57. Bruniales - [Bruniaceae + Columelliaceae] 58. Apiales - [Pennantiaceae [Torricelliaceae [Griseliniaceae [Pittosporaceae [Araliaceae [Myodocarpaceae + Apiaceae]]]]]] 59. Paracryphiales Paracryphiaceae 60. Dipsacales - [Adoxaceae [Diervillaceae [Caprifoliaceae [Linnaeaceae [Morinaceae [Dipsacaceae + Valerianaceae]]]]]] (IV) Merits and demerits of APG system of classification

12 Merits The APG classification system strictly adopts the phylogenetic principle of monophyly reconstructing the phylogeny on the basis of established monophyletic origin. It is based on the synthesis of information derived from multiple sources morphology, anatomy, embryology, palynology, phytochemistry, molecular biology, etc. Formal names have been given only to those groups (i. e. orders) where monophyly has been firmly established. In order to overcome the problem of paraphyly, the traditional separation of angiosperms into monocots and dicots has been discarded. Various monocot groups have been placed in between primitive dicots and advanced dicots, e. g. Poales are placed in between Magnoliales and Ranunculales. Cladograms evolutionary diagrams - based on morphological and molecular data are presented for showing the phylogenetic relationships, both within and among the monophyletic groups. The orders, such as Amborellales, Nymphaeales, Austrobaileyales, Chloranthales, which show several primitive features, are placed at the start of the APG classification. The number of unplaced and uncertain families has been gradually reduced from APG-I (40) to APG-III (10). Major changes have been carried out in the circumscription of several orders and families, which was also supported by some workers in the past. For instance, Liliaceae (sensu lato) has been split into several monophyletic families: Liliaceae (sensu stricto), Alliaceae, Asparagaceae, Asphodelaceae, etc. Similarly, circumscription of Malvaceae (sensu stricto) has been broadened to include Tiliaceae, Sterculiaceae and Bombacaceae, thus forming a monophyletic Malvaceae (sensu

13 lato). It is well known that a classification system presents a viewpoint prevailing at a particular time, based on the recent advances in research. The APG classification is increasingly becoming an authoritative point of reference and a significant number of major herbaria, including Kew, Harvard, etc. are arranging their plant specimen collections in accordance with APG. Demerits APG classification is restricted at the taxonomic levels of only order and family. The classification may seem to be sound in theory, but it has still found few followers in practice. Although majority of families or genera have been recognised as monophyletic orders, yet there are several unplaced families or genera in APG III. The orders have been recognised under informal groups (e.g. Magnoliids, Eudicots, etc), the names of which do not conform to the ICBN. Angiosperms have been given the rank of a division, followed by the rank of order. In contrast to the previous classification systems, there are no formal taxa between the rank of division and order.

Flowering plants - angiosperms

Flowering plants - angiosperms A spectacular terrestrial radiation Over 250,000 extant species Major lineages originated 130-90 million years ago Dramatic rise to dominance 100-70 million years ago We