The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a further revision, the APG IV system.
Along with the publication outlining the new system, there were two accompanying publications in the same issue of the Botanical Journal of the Linnean Society: The first, by Chase & Reveal, was a formal phylogenetic classification of all land plants (embryophytes), compatible with the APG III classification. As the APG have chosen to eschew ranks above order, this paper was meant to fit the system into the existing Linnaean hierarchy for those that prefer such a classification. The result was that all land plants were placed in the class Equisetopsida, which was then divided into 16 subclasses and a multitude of superorders. The second, by Haston et al., was a linear sequence of families following the APG III system (LAPG III). This provided a numbered list to the 413 families of APG III. A linear sequence is of particular use to herbarium curators and those working on floristic works wishing to arrange their taxa according to APG III.Haston, E., Richardson, J.E., Stevens, P.F., Chase, M.W., Harris, D.J. (2009) The Linear Angiosperm Phylogeny Group (LAPG) III: a linear sequence of the families in APG III. Botanical Journal of the Linnean Society 161, 128–131.
Organization The APG III system recognized all of the 45 orders of the previous system, as well as 14 new ones. The order Ceratophyllales was erroneously marked as a new order, as it had been recognized in both of the previous APG systems. The newly recognized orders were: Amborellales, Nymphaeales, Chloranthales, Petrosaviales, Trochodendrales, Buxales, Vitales, Zygophyllales, Picramniales, Huerteales, Berberidopsidales, Escalloniales, Bruniales, and Paracryphiales.
The designation of alternative "bracketed families" was abandoned in APG III, because its inclusion in the previous system had been unpopular. APG III recognized 413 families, 43 fewer than in the previous system. Forty-four of the 55 "bracketed families" were discontinued, and 20 other families were discontinued as well.
The discontinued bracketed families were: Illiciaceae, Alliaceae, Agapanthaceae, Agavaceae, Aphyllanthaceae, Hesperocallidaceae, Hyacinthaceae, Laxmanniaceae, Ruscaceae, Themidaceae, Asphodelaceae, Hemerocallidaceae, Kingdoniaceae, Fumariaceae, Pteridophyllaceae, Didymelaceae, Tetracentraceae, Pterostemonaceae, Hypseocharitaceae, Francoaceae, Memecylaceae, Lepuropetalaceae, Rhoipteleaceae, Medusagynaceae, Quiinaceae, Malesherbiaceae, Turneraceae, Bretschneideraceae, Diegodendraceae, Cochlospermaceae, Peganaceae, Tetradiclidaceae, Nyssaceae, Ternstroemiaceae, Pellicieraceae, Aucubaceae, Donatiaceae, Lobeliaceae, Desfontainiaceae, Diervillaceae, Dipsacaceae, Linnaeaceae, Morinaceae, and Valerianaceae.
The other discontinued families were: Limnocharitaceae, Luzuriagaceae, Sparganiaceae, Ixerbaceae, Ledocarpaceae, Heteropyxidaceae, Psiloxylaceae, Oliniaceae, Rhynchocalycaceae, Parnassiaceae, Maesaceae, Myrsinaceae, Theophrastaceae, Eremosynaceae, Polyosmaceae, Tribelaceae, Sphenostemonaceae, Aralidiaceae, Mackinlayaceae, and Melanophyllaceae.
21 families were accepted in the APG III system which had not been in the previous system, and a few families were moved to a different position. The newly recognized families are: Cynomoriaceae, Haptanthaceae, Petermanniaceae, Schoepfiaceae, Limeaceae, Lophiocarpaceae, Montiaceae, Talinaceae, Anacampserotaceae, Centroplacaceae, Calophyllaceae, Guamatelaceae, Gerrardinaceae, Dipentodontaceae, Capparidaceae, Cleomaceae, Cytinaceae, Mitrastemonaceae, Metteniusaceae, Linderniaceae, and Thomandersiaceae.
The number of families not placed in any order was reduced from 39 to 10. Apodanthaceae and Cynomoriaceae were placed among the angiosperms, incertae sedis, that is, not in any group within the angiosperms. Eight other families were placed incertae sedis in various supra-ordinal groups within the angiosperms. The families not placed in any order were: Apodanthaceae, Cynomoriaceae, Dasypogonaceae, Sabiaceae, Dilleniaceae, Icacinaceae, Metteniusaceae, Oncothecaceae, Vahliaceae, and Boraginaceae.
The paragraph below shows the number of families in each order and the placement of those families that were not included in any order. These figures were produced by simply counting the families in the text of the paper that established APG III.
ORDERS: Amborellales (1), Nymphaeales (3), Austrobaileyales (3), Chloranthales (1), Canellales (2), Piperales (5), Magnoliales (6), Laurales (7), Acorales (1), Alismatales (13), Petrosaviales (1), Dioscoreales (3), Pandanales (5), Liliales (10), Asparagales (14), Arecales (1), Poales (16), Commelinales (5), Zingiberales (8), Ceratophyllales (1), Ranunculales (7), Proteales (3), Trochodendrales (1), Buxales (2), Gunnerales (2), Saxifragales (14), Vitales (1), Zygophyllales (2), Celastrales (2), Oxalidales (7), Malpighiales (35), Fabales (4), Rosales (9), Fagales (7), Cucurbitales (7), Geraniales (3), Myrtales (9), Crossosomatales (7), Picramniales (1), Sapindales (9), Huerteales (3), Brassicales (17), Malvales (10), Berberidopsidales (2), Santalales (7), Caryophyllales (34), Cornales (6), Ericales (22), Garryales (2), Gentianales (5), Solanales (5), Lamiales (23), Aquifoliales (5), Asterales (11), Escalloniales (1), Bruniales (2), Apiales (7), Paracryphiales (1), Dipsacales (2).
SUPRA-ORDINAL GROUPS: commelinids (1), basal eudicots (1), Pentapetalae (1), lamiids incertae sedis (3), core lamiids (2), angiosperms incertae sedis (2).
The circumscription of the family Icacinaceae remains especially doubtful. Apodytes and its close relative, Rhaphiostylis, as well as Emmotum, Cassinopsis, and a few other genera were provisionally retained within it until further studies can determine whether they properly belong there.
Three genera (Gumillea, Nicobariodendron, and Petenaea) were placed within the angiosperms incertae sedis. Gumillea had been unplaced in APG II. Nicobariodendron and Petenaea were newly added to the list. The latter was later placed into its own family Petenaeaceae in the order HuertealesChristenhusz, M. J. M., M. F. Fay, J. J. Clarkson, P. Gasson, J. Morales Can, J. B. Jimenez Barrios & M. W. Chase (2010). Petenaeaceae, a new angiosperm family in Huerteales with a distant relationship to Gerrardina (Gerrardinaceae), Botanical Journal of the Linnean Society 164: 16-25. http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8339.2010.01074.x/abstractChristenhusz, M. J. M., M. W. Chase, & M.F.Fay (2011). Preface to "Linear sequence, classification, synonymy, and bibliography of vascular plants: Lycophytes, ferns, gymnosperms and angiosperms", Phytotaxa 19: 4–6. http://www.mapress.com/phytotaxa/content/2011/f/pt00019p006.pdf
The classification is shown below in two versions. The short version goes to the level of orders and of families unplaced in an order. The detailed version shows all the families. Orders at the same level in the classification are arranged alphabetically. Note that orders may not contain the same families as in earlier versions of the APG system (APG system, APG II system). Further detail on relationships can be seen in the phylogenetic tree below.
Short version clade angiosperms order Amborellales order Nymphaeales order Austrobaileyales order Chloranthales clade magnoliids order Canellales order Laurales order Magnoliales order Piperales clade monocots order Acorales order Alismatales order Asparagales order Dioscoreales order Liliales order Pandanales order Petrosaviales clade commelinids family Dasypogonaceae—unplaced in an order order Arecales order Commelinales order Poales order Zingiberales probable sister of eudicots order Ceratophyllales clade eudicots family Sabiaceae—unplaced in an order order Buxales order Proteales order Ranunculales order Trochodendrales clade core eudicots family Dilleniaceae—unplaced in an order order Gunnerales order Saxifragales clade rosids order Vitales clade fabids (eurosids I) order Celastrales order Cucurbitales order Fabales order Fagales order Malpighiales order Oxalidales order Rosales order Zygophyllales clade malvids (eurosids II) order Brassicales order Crossosomatales order Geraniales order Huerteales order Malvales order Myrtales order Picramniales order Sapindales (back to core eudicots) order Berberidopsidales order Caryophyllales order Santalales clade asterids order Cornales order Ericales clade lamiids (euasterids I) family Boraginaceae—unplaced in an order family Vahliaceae—unplaced in an order family Icacinaceae—unplaced in an order family Metteniusaceae—unplaced in an order family Oncothecaceae—unplaced in an order order Garryales order Gentianales order Lamiales order Solanales clade campanulids (euasterids II) order Apiales order Aquifoliales order Asterales order Bruniales order Dipsacales order Escalloniales order Paracryphiales
Detailed version Legend:
* = new family placement; † = newly recognized order for the APG system; § = new family circumscription described in the text; $ = families that represent the broader circumscription of options available in APG II and favoured here; $$ = families that were in square brackets in APG II, the narrower circumscriptions favoured here.
Angiosperms †Amborellales Melikyan, A.V.Bobrov & Zaytzeva Amborellaceae Pichon †Nymphaeales Salisb. ex Bercht. & J.Presl $$Cabombaceae Rich. ex A.Rich. *Hydatellaceae U.Hamann $$Nymphaeaceae Salisb. Austrobaileyales Takht. ex Reveal Austrobaileyaceae Croizat $Schisandraceae Blume (including Illiciaceae A.C.Sm.) Trimeniaceae L.S.Gibbs †Chloranthales R.Br. Chloranthaceae R.Br. ex Sims
Magnoliids Canellales Cronquist Canellaceae Mart. Winteraceae R.Br. ex Lindl. Piperales Bercht. & J.Presl Aristolochiaceae Juss. Hydnoraceae C.Agardh Lactoridaceae Engl. Piperaceae Giseke Saururaceae F.Voigt Laurales Juss. ex Bercht. & J.Presl Atherospermataceae R.Br. Calycanthaceae Lindl. Gomortegaceae Reiche Hernandiaceae Blume Lauraceae Juss. Monimiaceae Juss. Siparunaceae Schodde Magnoliales Juss. ex Bercht. & J.Presl Annonaceae Juss. Degeneriaceae I.W.Bailey & A.C.Sm. Eupomatiaceae Orb. Himantandraceae Diels Magnoliaceae Juss. Myristicaceae R.Br.
Monocots Acorales Link Acoraceae Martinov Alismatales R.Br. ex Bercht. & J.Presl §Alismataceae Vent. (including Limnocharitaceae Takht. ex Cronquist) Aponogetonaceae Planch. Araceae Juss. Butomaceae Mirb. Cymodoceaceae Vines Hydrocharitaceae Juss. Juncaginaceae Rich. Posidoniaceae Vines Potamogetonaceae Bercht. & J.Presl Ruppiaceae Horan. Scheuchzeriaceae F.Rudolphi Tofieldiaceae Takht. Zosteraceae Dumort. †Petrosaviales Takht. Petrosaviaceae Hutch. Dioscoreales R.Br. Burmanniaceae Blume Dioscoreaceae R.Br. Nartheciaceae Fr. ex Bjurzon Pandanales R.Br. ex Bercht. & J.Presl Cyclanthaceae Poit. ex A.Rich. Pandanaceae R.Br. Stemonaceae Caruel Triuridaceae Gardner Velloziaceae J.Agardh Liliales Perleb §Alstroemeriaceae Dumort. (including Luzuriagaceae Lotsy) Campynemataceae Dumort. Colchicaceae DC. Corsiaceae Becc. Liliaceae Juss. Melanthiaceae Batsch ex Borkh. *Petermanniaceae Hutch. Philesiaceae Dumort. Ripogonaceae Conran & Clifford Smilacaceae Vent. Asparagales Link $Amaryllidaceae J.St.-Hil. (including Agapanthaceae F.Voigt, Alliaceae Borkh.) $Asparagaceae Juss. (including Agavaceae Dumort., Aphyllanthaceae Burnett, Hesperocallidaceae Traub, Hyacinthaceae Batsch ex Borkh., Laxmanniaceae Bubani, Ruscaceae M.Roem., Themidaceae Salisb.) Asteliaceae Dumort. Blandfordiaceae R.Dahlgren & Clifford Boryaceae M.W.Chase, Rudall & Conran Doryanthaceae R.Dahlgren & Clifford Hypoxidaceae R.Br. Iridaceae Juss.