APG system

Last updated

The APG system (Angiosperm Phylogeny Group system) of plant classification is the first version of a modern, mostly molecular-based, system of plant taxonomy. Published in 1998 by the Angiosperm Phylogeny Group, it was replaced by the improved APG II in 2003, APG III system in 2009 and APG IV system in 2016.



The original APG system is unusual in being based, not on total evidence, but on the cladistic analysis of the DNA sequences of three genes, two chloroplast genes and one gene coding for ribosomes. Although based on molecular evidence only, its constituent groups prove to be supported by other evidence as well, for example pollen morphology supports the split between the eudicots and the rest of the former dicotyledons.

The system is rather controversial in its decisions at the family level, splitting a number of long-established families and submerging some other families. It also is unusual in not using botanical names above the level of order, that is, an order is the highest rank that will have a formal botanical name in this system. Higher groups are defined only as clades, with names such as monocots, eudicots, rosids, asterids.

The APG system was superseded in 2003 by a revision, the APG II system, in 2009 by a next revision, the APG III system, and then in 2016 by a further revision, the APG IV system.


The main groups in the system (all unranked clades) are:

Representation in color

The APG system recognises 462 families and 40 orders: these are assigned as follows. In the beginning of each listing some families or orders that are not placed in a further clade:

Note: "+ ..." = optional seggregrate family, that may be split off from the preceding family.

See also

Related Research Articles

Malpighiales Eudicot order of flowering plants

The Malpighiales comprise one of the largest orders of flowering plants, containing about 36 families and more than 16,000 species, about 7.8% of the eudicots. The order is very diverse, containing plants as different as the willow, violet, poinsettia, manchineel, rafflesia and coca plant, and are hard to recognize except with molecular phylogenetic evidence. It is not part of any of the classification systems based only on plant morphology. Molecular clock calculations estimate the origin of stem group Malpighiales at around 100 million years ago (Mya) and the origin of crown group Malpighiales at about 90 Mya.

Sapindales Order of flowering plants

Sapindales is an order of flowering plants. Well-known members of Sapindales include citrus; maples, horse-chestnuts, lychees and rambutans; mangos and cashews; frankincense and myrrh; mahogany and neem.

Ranunculales Basal order of flowering plants in the eudicots

Ranunculales is an order of flowering plants. Of necessity it contains the family Ranunculaceae, the buttercup family, because the name of the order is based on the name of a genus in that family. Ranunculales belongs to a paraphyletic group known as the basal eudicots. It is the most basal clade in this group; in other words, it is sister to the remaining eudicots. Widely known members include poppies, barberries, and buttercups.

Geraniales Order of flowering plants in the rosid subclade of eudicots

Geraniales are 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.

Celastrales Order of flowering plants, mostly from tropics and subtropics

The Celastrales are an order of flowering plants found throughout the tropics and subtropics, with only a few species extending far into the temperate regions. The 1200 to 1350 species are in about 100 genera. All but seven of these genera are in the large family Celastraceae. Until recently, the composition of the order and its division into families varied greatly from one author to another.

Primulaceae Family of flowering plants that includes the primroses

The Primulaceae, commonly known as the primrose family, are a family of herbaceous and woody flowering plants including some favourite garden plants and wildflowers. Most are perennial though some species, such as scarlet pimpernel, are annuals.

Burmanniaceae Family of flowering plants

Burmanniaceae is a family of flowering plants, consisting of 99 species of herbaceous plants in eight genera.

Angiosperm Phylogeny Group Collaborative research group for the classification of flowering plants

The Angiosperm Phylogeny Group (APG) is an informal international group of systematic botanists who collaborate to establish a consensus on the taxonomy of flowering plants (angiosperms) that reflects new knowledge about plant relationships discovered through phylogenetic studies.

Eudicots Clade of flowering plants

The eudicots, Eudicotidae or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons.

Rosids Large clade of flowering plants

The rosids are members of a large clade of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms.

Asterids Clade of Eudicot Angiosperms

In the APG IV system (2016) for the classification of flowering plants, the name asterids denotes a clade. Asterids is the largest group of flowering plant with more than 80,000 species, about a third of the total flowering plant species. Well known plants in this clade include the common daisy, forget-me-nots, nightshades, the common sunflower, petunias, yacon, morning glory, sweet potato, coffee, lavender, lilac, olive, jasmine, honeysuckle, ash tree, teak, snapdragon, sesame, psyllium, garden sage, table herbs such as mint, basil, and rosemary, and rainforest trees such as Brazil nut.

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.

Commelinids A clade of monocot flowering plants

In plant taxonomy, commelinids is a clade of flowering plants within the monocots, distinguished by having cell walls containing ferulic acid.

Boraginales Order of flowering plants within the lammiid clade of eudicots

Boraginales is a valid taxonomic name at the rank of order for a group of flowering plants. It includes Boraginaceae and closely related asterid families. The Boraginales include about 125 genera, 2,700 species and its herbs, shrubs, trees and lianas (vines) have a worldwide distribution.

<i>Hanguana</i> Genus of flowering plants

Hanguana is a genus of flowering plants with a dozen known species. It is the only genus in the family Hanguanaceae.

Caryophyllales Order of flowering plants

Caryophyllales is a diverse and heterogeneous order of flowering plants that includes the cacti, carnations, amaranths, ice plants, beets, and many carnivorous plants. Many members are succulent, having fleshy stems or leaves. The betalain pigments are unique in plants of this order and occur in all its families with the exception of Caryophyllaceae and Molluginaceae.

Mesangiospermae One of two clades of flowering plants

Mesangiospermae is a clade of flowering plants (angiosperms), informally called "mesangiosperms". They are one of two main groups of angiosperms. It is a name created under the rules of the PhyloCode system of phylogenetic nomenclature. There are about 350,000 species of mesangiosperms. The mesangiosperms contain about 99.95% of the flowering plants, assuming that there are about 175 species not in this group and about 350,000 that are. While such a clade with a similar circumscription exists in the APG III system, it was not given a name.

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.

Huaceae Family of flowering plants

Huaceae is a family of plant in the rosids group, which has been classed in the orders Malpighiales, Malvales, and Violales or in its own order Huales. The APG II system placed it in the clade eurosids I, whereas the APG III system of 2009 and APG IV (2016) place it within the Oxalidales. The family is endemic to central Africa. It contains four species in the following two genera:

Superasterids Clade of flowering plants

The superasterids are members of a large clade of flowering plants, containing more than 122,000 species.