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The APG system was superseded in 2003 by a revision, the APG II system, in 2009 by a next revision, the APG III system, and then in 2016 by a further revision, the APG IV system.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:
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.
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 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 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, hellebores, and buttercups.
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.
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 is a family of flowering plants, consisting of 99 species of herbaceous plants in eight genera.
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.
The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants (angiosperms) which are mainly characterized by having two seed leaves (cotyledons) upon germination. The term derives from dicotyledon. Previously, they were called tricolpates or non-magnoliid dicots by past authors. The current botanical terms were introduced in 1991, by evolutionary botanist James A. Doyle and paleobotanist Carol L. Hotton, to emphasize the later evolutionary divergence of tricolpate dicots from earlier, less specialized, dicots.
The rosids are members of a large clade of flowering plants, containing about 70,000 species, more than a quarter of all 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 plants, 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, lettuce, 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.
In plant taxonomy, commelinids is a clade of flowering plants within the monocots, distinguished by having cell walls containing ferulic acid.
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.
The basal angiosperms are the flowering plants which diverged from the lineage leading to most flowering plants. In particular, the most basal angiosperms were called the ANITA grade, which is made up of Amborella, Nymphaeales and Austrobaileyales.
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 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:
The superrosids are members of a large clade of flowering plants, containing more than 88,000 species, and thus more than a quarter of all angiosperms.
In phylogenetic nomenclature, the Pentapetalae are a large group of eudicots that were informally referred to as the "core eudicots" in some papers on angiosperm phylogenetics. They comprise an extremely large and diverse group accounting for about 65% of the species richness of the angiosperms, with wide variability in habit, morphology, chemistry, geographic distribution, and other attributes. Classical systematics, based solely on morphological information, was not able to recognize this group. In fact, the circumscription of the Pentapetalae as a clade is based on strong evidence obtained from DNA molecular analysis data.
The superasterids are members of a large clade of flowering plants, containing more than 122,000 species.