APG II system

The APG II system (Angiosperm Phylogeny Group 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April 2003 by the Angiosperm Phylogeny Group.[1] It was a revision of the first APG system, published in 1998, and was superseded in 2009 by a further revision, the APG III system.

History

APG II was published as:

Each of the APG systems represents the broad consensus of a number of systematic botanists, united in the APG, working at several institutions worldwide.

The APG II system recognized 45 orders, five more than the APG system. The new orders were Austrobaileyales, Canellales, Gunnerales, Celastrales, and Crossosomatales, all of which were families unplaced as to order, although contained in supra-ordinal clades, in the APG system. APG II recognized 457 families, five fewer than the APG system. Thirty-nine of the APG II families were not placed in any order, but 36 of the 39 were placed in a supra-ordinal clade within the angiosperms. Fifty-five of the families came to be known as "bracketed families". They were optional segregates of families that could be circumscribed in a larger sense.

The APG II system was influential and was adopted in whole or in part (sometimes with modifications) in a number of references. It was superseded 6½ years later by the APG III system, published in October 2009.

Groups

FlowerPlantsSystemTreeEn
Cladogram showing the relationships, but excluding taxa not placed within an order

Main groups in the system (all unranked clades between the ranks of class and order):

Shown below is the classification in full detail, except for the fifteen genera and three families that were unplaced in APG II. The unplaced taxa were listed at the end of the appendix in a section entitled "Taxa of Uncertain Position". Under some of the clades are listed the families that were placed incertae sedis in that clade. Thirty-six families were so placed. This means that their relationship to other members of the clade is not known.

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

References

  1. ^ Angiosperm Phylogeny Group (2003). An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II. Botanical Journal of the Linnean Society 141(4): 399-436. doi: 10.1046/j.1095-8339.2003.t01-1-00158.x

Note: This is a selected list of the more influential systems. There are many other systems, for instance a review of earlier systems, published by Lindley in his 1853 edition, and Dahlgren (1982). Examples include the works of Scopoli, Batsch and Grisebach.

Aquifoliales

The Aquifoliales are an order of flowering plants, including the Aquifoliaceae (or holly) family, and also the Helwingiaceae (2-5 species of temperate Asian shrubs) and the Phyllonomaceae (4 species of Central American trees and shrubs). In 2001, the families Stemonuraceae and Cardiopteridaceae were added to this order. This circumscription of Aquifoliales was recognized by the Angiosperm Phylogeny Group when they published the APG II system in 2003. In the Cronquist system, there is no Aquifoliales order: the Aquifoliaceae are placed within the order Celastrales and the others are in other families.

Brassicales

The Brassicales (or Cruciales) are an order of flowering plants, belonging to the eurosids II group of dicotyledons under the APG II system. One character common to many members of the order is the production of glucosinolate (mustard oil) compounds. Most systems of classification have included this order, although sometimes under the name Capparales (the name chosen depending on which is thought to have priority).The order typically contains the following families:

Akaniaceae - two species of turnipwood trees, native to Asia and eastern Australia

Bataceae – salt-tolerant shrubs from America and Australasia

Brassicaceae – mustard and cabbage family; may include the Cleomaceae

Capparaceae – caper family, sometimes included in Brassicaceae

Caricaceae – papaya family

Cleomaceae

Gyrostemonaceae - several genera of small shrubs and trees endemic to temperate parts of Australia

Koeberliniaceae - one species of thorn bush native to Mexico and the US Southwest

Limnanthaceae – meadowfoam family

Moringaceae – thirteen species of trees from Africa and India

Pentadiplandraceae - African species whose berries have two highly sweet tasting proteins

Resedaceae – mignonette family

Salvadoraceae - three genera found from Africa to Java

Setchellanthaceae

Tovariaceae

Tropaeolaceae – nasturtium familyUnder the Cronquist system, the Brassicales were called the Capparales, and included among the "Dilleniidae". The only families included were the Brassicaceae and Capparaceae (treated as separate families), the Tovariaceae, Resedaceae, and Moringaceae. Other taxa now included here were placed in various other orders.

The families Capparaceae and Brassicaceae are closely related. One group, consisting of Cleome and related genera, was traditionally included in the Capparaceae but doing so results in a paraphyletic Capparaceae. Therefore, this group is generally now either included in the Brassicaceae or as its own family, Cleomaceae.

Callitriche

Callitriche is a genus of largely aquatic plants known as water-starwort. Previously, it was the only genus in the family Callitrichaceae. However, according to the APG II system this family is now included in the Plantaginaceae (plantain family). The family name Callitrichaceae retains its status as nomen conservandum (name to be retained).

Dilleniales

The Dilleniales are an order of flowering plants, potentially containing one family, Dilleniaceae. The APG III system of 2009, like the earlier APG II system of 2003, left the Dilleniaceae unplaced as to order, while noting that the name Dilleniales was available. Stevens at the Angiosperm Phylogeny Website has subsequently placed Dilleniaceae in the order Dilleniales.The Cronquist system, of 1981, recognized such an order and placed it in subclass Dilleniidae. It used the following circumscription:

order Dilleniales

family Dilleniaceae

family PaeoniaceaeThe Takhtajan system of 1969 had the families Dilleniaceae and Crossosomataceae in the order.The APG III system assigned the second of these families, the Paeoniaceae, to the order Saxifragales.

Dioscoreaceae

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 (some species of Dioscorea).

The APG system (1998) and APG II system (2003) both place it in the order Dioscoreales, in the clade monocots. However, the circumscription changed in the APG II system, with the 2003 system expanded to include the plants that in the 1998 system were treated in the families Taccaceae and Trichopodaceae.

Dipsacales

The Dipsacales are an order of flowering plants, included within the asterid group of dicotyledons. In the APG III system of 2009, the order includes only two families, Adoxaceae and a broadly defined Caprifoliaceae. Some well-known members of the Dipsacales order are honeysuckle, elder, viburnum, and valerian.

Under the Cronquist system, the order included Adoxaceae, Caprifoliaceae sensu stricto, Dipsacaceae, and Valerianaceae. Under the 2003 APG II system, the circumscription of the order was much the same but the system allowed either a broadly circumscribed Caprifoliaceae including the families Diervillaceae, Dipsacaceae, Linnaeaceae, Morinaceae, and Valerianaceae, or these families being kept separate. The APG III system only uses the broadly circumscribed Caprifoliceae.The Dipsacales appear to be most closely related to the Paracryphiales.

Escalloniaceae

Escalloniaceae is a family of flowering plants consisting of about 130 species in seven genera. In the APG II system it is one of eight families in the euasterids II clade (campanulids) that are unplaced as to order. More recent research has provided evidence that two of those families, Eremosynaceae and Tribelaceae, arose from within Escalloniaceae; the Angiosperm Phylogeny Website therefore merges these two families into Escalloniaceae, and also places the family alone in order Escalloniales.Genera:

Anopterus

Eremosyne

Escallonia

Forgesia

Polyosma

Tribeles

Valdivia

Lecythidaceae

The Lecythidaceae comprise a family of about 20 genera and 250-300 species of woody plants native to tropical South America, Africa (including Madagascar), Asia and Australia.

According to the most recent molecular analysis of Lecythidaceae by Mori et al. (2007), the three subfamilies are:

Foetidioideae (Foetidiaceae) from Madagascar include only Foetidia.

Planchonioideae (including Barringtonia) are restricted to the Old World tropics.

Lecythidoideae (Lecythidaceae) are restricted to the New World tropics.Two other families are sometimes included in Lecythidaceae; the Scytopetalaceae and Napoleonaeaceae are hypothesized as most closely related to Lecythidaceae.

More detailed information about Lecythidaceae, especially the New World taxa, can be found at the Lecythidaceae Pages.

The most important member of the family in world trade is the Brazil nut (Bertholletia excelsa), valued for its edible nuts; the paradise nut (Lecythis species) is also eaten.

The APG II system of 2003 includes genera from the family Scytopetalaceae in the Lecythidaceae, including Rhaptopetalum and Brazzeia. Careya is called pezham in Malayalam.

Loranthaceae

Loranthaceae, commonly known as the showy mistletoes, is a family of flowering plants. It consists of about 75 genera and 1,000 species of woody plants, many of them hemiparasites. The three terrestrial species are Nuytsia floribunda (the Western Australian Christmas tree), Atkinsonia ligustrina (from the Blue Mountains of Australia), and Gaiadendron punctatum (from Central/South America.) Loranthaceae are primarily xylem parasites, but their haustoria may sometimes tap the phloem, while Tristerix aphyllus is almost holoparasitic.

For a more complete description of the Australian Loranthaceae, see Flora of Australia online., for the Malesian Loranthaceae see Flora of Malesia.

Originally, Loranthaceae contained all mistletoe species, but the mistletoes of Europe and North America (Viscum and Phoradendron) belong to the family Santalaceae. The APG II system 2003 assigns the family to the order Santalales in the clade core eudicots.

Malvales

The Malvales are an order of flowering plants. As circumscribed by APG II-system, the order includes about 6000 species within 9 families. The order is placed in the eurosids II, which are part of the eudicots.

The plants are mostly shrubs and trees; most of its families have a cosmopolitan distribution in the tropics and subtropics, with limited expansion into temperate regions. An interesting distribution occurs in Madagascar, where three endemic families of Malvales (Sphaerosepalaceae, Sarcolaenaceae and Diegodendraceae) occur.

Many species of Malvaceae sensu lato are known for their wood, with that of Ochroma (balsa) being known for its lightness, and that of Tilia (lime, linden, or basswood) as a popular wood for carving. Fruit of the cacao tree (Theobroma cacao) are used as an ingredient for chocolate. Kola nuts (genus Cola) are notable for their high content of caffeine and, in past, were commonly used for preparing of various cola drinks. Other well-known members of Malvales in the APG II sense are daphnes, hibiscus, hollyhocks, okra, baobab trees, cotton, and kapok.

Melanthiaceae

Melanthiaceae, also called the bunchflower family, is a family of flowering perennial herbs native to the Northern Hemisphere. Along with many other lilioid monocots, early authors considered members of this family to belong to the family Liliaceae, in part because both their sepals and petals closely resemble each other and are often large and showy like those of lilies, while some more recent taxonomists have placed them in a family Trilliaceae. The most authoritative modern treatment, however, the APG III system of 2009 (unchanged from the 2003 APG II system and the 1998 APG system), places the family in the order Liliales, in the clade monocots. Circumscribed in this way, the family includes up to 17 genera.

Familiar members of the family include Herb Paris (Paris quadrifolia) and the trilliums.

Melianthaceae

The Melianthaceae are a family of flowering plants. The APG II system includes them within the rosid clade. All members of Melianthaceae proper are trees or shrubs found in tropical and southern Africa. Francoaceae (the Bridal wreaths) are sometimes included in the family, a family consisting of two monotypic genera found in Chile.

Plumbaginaceae

Plumbaginaceae is a family of flowering plants, with a cosmopolitan distribution. The family is sometimes referred to as the leadwort family or the plumbago family.

Most species in this family are perennial herbaceous plants, but a few grow as lianas or shrubs. The plants have perfect flowers and are pollinated by insects. They are found in many different climatic regions, from arctic to tropical conditions, but are particularly associated with salt-rich steppes, marshes, and sea coasts.

The family has been recognized by most taxonomists. The APG II system (2003; unchanged from the APG system of 1998), recognizes this family and assigns it to the order Caryophyllales in the clade core eudicots. It includes ca 30 genera and about 725 species.The 1981 Cronquist system placed the family in a separate order Plumbaginales, which included no other families. The Dahlgren system had segregated some of these plants as family Limoniaceae.

Portulacaceae

The Portulacaceae are a family of flowering plants, comprising 115 species in a single genus Portulaca. Formerly some 20 genera with about 500 species, were placed there, but it is now restricted to encompass only one genus, the other genera being placed elsewhere. The family has been recognised by most taxonomists, and is also known as the purslane family; it has a cosmopolitan distribution, with the highest diversity in semiarid regions of the Southern Hemisphere in Africa, Australia, and South America, but with a few species also extending north into Arctic regions. The family is very similar to the Caryophyllaceae, differing in the calyx, which has only two sepals.

The APG II system (2003; unchanged from the APG system of 1998) assigns it to the order Caryophyllales in the clade core eudicots. In the APG III system, several genera were moved to the Montiaceae, Didiereaceae, Anacampserotaceae and Talinaceae, thus making the family monotypic and only containing the genus Portulaca.

Posidonia

Posidonia is a genus of flowering plants. It contains nine species of marine plants ("seagrass"), found in the seas of the Mediterranean and around the south coast of Australia.

The APG system (1998) and APG II system (2003) accept this genus as constituting the sole genus in the family Posidoniaceae, which it places in the order Alismatales, in the clade monocots. The AP-Website concludes that the three families Cymodoceaceae, Posidoniaceae and Ruppiaceae form a monophyletic group. Earlier systems classified this genus in the family Potamogetonaceae or in the family Posidoniaceae but belonging to order Zosterales.

Santalaceae

The Santalaceae, sandalwoods, are a widely distributed family of flowering plants (including small trees, shrubs, perennial herbs, and epiphytic climbers) which, like other members of Santalales, are partially parasitic on other plants. Its flowers are bisexual or, by abortion ("flower drop"), unisexual. Modern treatments of the Santalaceae include the family Viscaceae (mistletoes), previously considered distinct.

The APG II system of 2003 recognises the family and assigns it to the order Santalales in the clade core eudicots. However, the circumscription by APG is much wider than accepted by previous classifications, including the plants earlier treated in families Eremolepidaceae and Viscaceae. It includes about 1,000 species in 43 genera.

Genera

excluded genera:

Arjona - to Schoepfiaceae

Quinchamalium - to Schoepfiaceae

Sapindales

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.

The APG III system of 2009 includes it in the clade malvids (in rosids, in eudicots) with the following nine families:

Anacardiaceae

Biebersteiniaceae

Burseraceae

Kirkiaceae

Meliaceae

Nitrariaceae (including Peganaceae and Tetradiclidaceae)

Rutaceae

Sapindaceae

SimaroubaceaeThe APG II system of 2003 allowed the optional segregation of families now included in the Nitrariaceae.

In the classification system of Dahlgren the Rutaceae were placed in the order Rutales, in the superorder Rutiflorae (also called Rutanae). The Cronquist system of 1981 used a somewhat different circumscription, including the following families:

Staphyleaceae

Melianthaceae

Bretschneideraceae

Akaniaceae

Sapindaceae

Hippocastanaceae

Aceraceae

Burseraceae

Anacardiaceae

Julianiaceae

Simaroubaceae

Cneoraceae

Meliaceae

Rutaceae

ZygophyllaceaeThe difference from the APG III system is not as large as may appear, as the plants in the families Aceraceae and Hippocastanaceae stay in this order at APG III (both included in family Sapindaceae). The species now composing the family Nitrariaceae in APG III also belonged to this order in the Cronquist system as part of the family Zygophyllaceae, while those now in the family Kirkiaceae were present as part of the family Simaroubaceae.

Strelitziaceae

The Strelitziaceae comprise a family of monocotyledonous flowering plants, very similar in appearance and growth habit to members of the related families Heliconiaceae and Musaceae (banana family). The three genera with seven species of Strelitziaceae have been included in Musaceae in some classifications, but are generally recognized as a separate family in more recent treatments such as the APG II system (2003). The APG II system assigns the Strelitziaceae to the order Zingiberales in the commelinid clade.

Tiliaceae

Tiliaceae () is a botanical name for a family of flowering plants. It is not a part of the APG, APG II and APG III classifications, being sunk in Malvaceae but has an extensive historical record of use.

All through its existence the family has had a very lively history, with various authors taking very different views on what should be part of this family. As a result, it is recommended when this name is encountered to check what the author means.

However, in the northern temperate regions the name is unambiguous as the only representative is Tilia, the lime or linden.

Pre-Linnaean
Pre-Darwinian
Post-Darwinian (Phyletic)
Angiosperm Phylogeny Group
System (1998–2009)
See also

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