See also: Angiosperm Phylogeny Group. 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 Published in 2009, it was superseded in 2016 by a further revision, the APG IV system.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 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 Huerteales[2] [3]
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.
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
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.
The APG III system was based on a phylogenetic tree for the angiosperms which included all of the 59 orders and 4 of the unplaced families. The systematic positions of the other 6 unplaced families was so uncertain that they could not be placed in any of the polytomies in the tree. They are shown in the classification table entitled "Detailed version" above, 4 in Euasterids I and 2 in Taxa of uncertain position.
The phylogenetic tree shown below was published with the APG III system, but without some of the labels that are added here.
A number of subfamilies have been proposed to replace some of the families which were optional (i.e. bracketed) in APG II, but have been discontinued in APG III. These are shown in the table below.
| Agapanthaceae | Amaryllidaceae: Agapanthoideae | |
| Agavaceae | Asparagaceae: Agavoideae | |
| Alliaceae | Amaryllidaceae: Allioideae | |
| Amaryllidaceae | Amaryllidaceae: Amaryllidoideae | |
| Aphyllanthaceae | Asparagaceae: Aphyllanthoideae | |
| Asparagaceae | Asparagaceae: Asparagoideae | |
| Asphodelaceae | Xanthorrhoeaceae: Asphodeloideae | |
| Hemerocallidaceae | Xanthorrhoeaceae: Hemerocallidoideae | |
| Hesperocallidaceae | Asparagaceae: Agavoideae | |
| Hyacinthaceae | Asparagaceae: Scilloideae | |
| Laxmanniaceae | Asparagaceae: Lomandroideae | |
| Ruscaceae | Asparagaceae: Nolinoideae | |
| Themidaceae | Asparagaceae: Brodiaeoideae | |
| Xanthorrhoeaceae | Xanthorrhoeaceae: Xanthorrhoeoideae |