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 Published in 2009, it was superseded in 2016 by a further revision, the APG IV system. [1] [2] [3]
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:
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:
The other discontinued families were:
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:
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:
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. [1]
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 [6] [7]
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.
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, [1] but without some of the labels that are added here.
angiosperms |
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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. [8] These are shown in the table below.
APG II bracketed family | APG III family: subfamily |
---|---|
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 |
The Myrtales are an order of flowering plants placed as a sister to the eurosids II clade as of the publishing of the Eucalyptus grandis genome in June 2014.
The Santalales are an order of flowering plants with a cosmopolitan distribution, but heavily concentrated in tropical and subtropical regions. It derives its name from its type genus Santalum (sandalwood). Mistletoe is the common name for a number of parasitic plants within the order.
Nepenthales is an order of carnivorous flowering plants in the Cronquist system of plant classification.
Dioscoreaceae is a family of monocotyledonous flowering plants, with about 715 known species in nine genera. The best-known member of the family is the yam.
Geraniales is a small order of flowering plants, included within the rosid subclade of eudicots. The largest family in the order is Geraniaceae with over 800 species. In addition, the order includes the smaller Francoaceae with about 40 species. Most Geraniales are herbaceous, but there are also shrubs and small trees.
The Buxales are a small order of eudicot flowering plants, recognized by the APG IV system of 2016. The order includes the family Buxaceae; the families Didymelaceae and Haptanthaceae may also be recognized or may be included in the Buxaceae. Many members of the order are evergreen shrubs or trees, although some are herbaceous perennials. They have separate "male" (staminate) and "female" (carpellate) flowers, mostly on the same plant. Some species are of economic importance either for the wood they produce or as ornamental plants.
Petrosaviaceae is a family of flowering plants belonging to a monotypic order, Petrosaviales. Petrosaviales are monocots, and are grouped within the lilioid monocots. Petrosaviales are a very small order of photosynthetic (Japonolirion) and rare leafless achlorophyllous, mycoheterotrophic plants (Petrosavia) found in dark montane rainforests in Japan, China, Southeast Asia and Borneo. They are characterised by having bracteate racemes, pedicellate flowers, six persistent tepals, septal nectaries, three almost distinct carpels, simultaneous microsporogenesis, monosulcate pollen, and follicular fruit.
The APG II system of plant classification is the second, now obsolete, version of a modern, mostly molecular-based, system of plant taxonomy that was published in April 2003 by the Angiosperm Phylogeny Group. It was a revision of the first APG system, published in 1998, and was superseded in 2009 by a further revision, the APG III system.
A system of plant taxonomy, the Takhtajan system of plant classification was published by Armen Takhtajan, in several versions from the 1950s onwards. It is usually compared to the Cronquist system. It admits paraphyletic groups.
Dasypogonaceae is a family of flowering plants, one that has not been commonly recognized by taxonomists; the plants it contains were usually included in the family Xanthorrhoeaceae. If valid, Dasypogonaceae includes four genera with 16 species.
The Rapateaceae are a family of flowering plants. The botanical name has been recognized by most taxonomists.
Boraginales is an order of flowering plants in the asterid clade. It includes the Boraginaceae and a number of other families, with a total of about 125 genera and 2,700 species. Its herbs, shrubs, trees and lianas (vines) have a worldwide distribution.
Loasaceae is a family of 15–20 genera and about 200–260 species of flowering plants in the order Cornales, native to the Americas and Africa. Members of the family include annual, biennial and perennial herbaceous plants, and a few shrubs and small trees. Members of the subfamily Loasoideae are known to exhibit rapid thigmonastic stamen movement when pollinators are present.
Magnoliidae is a subclass of Equisetopsida in the sense used by Mark W. Chase and James L. Reveal in their 2009 article "A phylogenetic classification of the land plants to accompany APG III." This subclass comprises the angiosperms or flowering plants.
The Aptandraceae is a family of flowering plants in the sandalwood order Santalales that is recognized by some sources; others sink the family in Olacaceae. The members of the tropical plant family are parasitic on other plants, usually on the roots, and grow as trees, shrubs or woody lianas.
The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was published in 2016, seven years after its predecessor the APG III system was published in 2009, and 18 years after the first APG system was published in 1998. In 2009, a linear arrangement of the system was published separately; the APG IV paper includes such an arrangement, cross-referenced to the 2009 one.
The Pteridophyte Phylogeny Group, or PPG, is an informal international group of systematic botanists who collaborate to establish a consensus on the classification of pteridophytes that reflects knowledge about plant relationships discovered through phylogenetic studies. In 2016, the group published a classification for extant pteridophytes, termed "PPG I". The paper had 94 authors.