APG II system

See also: Angiosperm Phylogeny Group

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2003 by the Angiosperm Phylogeny Group.^[1] It was a revision of the first APG system, published in 1998, and was superseded in 2009 by a further revision, the APG III system.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

• 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. (Available online: Abstract | Full text (HTML) | Full text (PDF) doi: 10.1046/j.1095-8339.2003.t01-1-00158.x)

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 It was superseded 6½ years later by the APG III system, published in October 2009.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

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):

• angiosperms :

  magnoliids

  monocots

  commelinids

  eudicots

  core eudicots

  rosids

  eurosids I

  eurosids II

  asterids

  euasterids I

  euasterids II

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.

• angiosperms :

  paraphyletic grade basal angiosperms

  family Amborellaceae

  family Chloranthaceae

  family Nymphaeaceae [+ family Cabombaceae]

  order Austrobaileyales

  order Ceratophyllales

  clade magnoliids

  order Canellales

  order Laurales

  order Magnoliales

  order Piperales

  clade monocots

  family Petrosaviaceae

  order Acorales

  order Alismatales

  order Asparagales

  order Dioscoreales

  order Liliales

  order Pandanales

  clade commelinids

  family Dasypogonaceae

  order Arecales

  order Commelinales

  order Poales

  order Zingiberales

  clade eudicots

  family Buxaceae [+ family Didymelaceae]

  family Sabiaceae

  family Trochodendraceae [+ family Tetracentraceae]

  order Proteales

  order Ranunculales

  clade core eudicots

  family Aextoxicaceae

  family Berberidopsidaceae

  family Dilleniaceae

  order Gunnerales

  order Caryophyllales

  order Santalales

  order Saxifragales

  clade rosids

  family Aphloiaceae

  family Geissolomataceae

  family Ixerbaceae

  family Picramniaceae

  family Strasburgeriaceae

  family Vitaceae

  order Crossosomatales

  order Geraniales

  order Myrtales

  clade eurosids I

  family Zygophyllaceae [+ family Krameriaceae]

  family Huaceae

  order Celastrales

  order Cucurbitales

  order Fabales

  order Fagales

  order Malpighiales

  order Oxalidales

  order Rosales

  clade eurosids II

  family Tapisciaceae

  order Brassicales

  order Malvales

  order Sapindales

  clade asterids

  order Cornales

  order Ericales

  clade euasterids I

  family Boraginaceae

  family Icacinaceae

  family Oncothecaceae

  family Vahliaceae

  order Garryales

  order Gentianales

  order Lamiales

  order Solanales

  clade euasterids II

  family Bruniaceae

  family Columelliaceae [+ family Desfontainiaceae]

  family Eremosynaceae

  family Escalloniaceae

  family Paracryphiaceae

  family Polyosmaceae

  family Sphenostemonaceae

  family Tribelaceae

  order Apiales

  order Aquifoliales

  order Asterales

  order Dipsacales

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