APG II system explained

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April 2003 by the Angiosperm Phylogeny Group.[1] It was a revision of the first APG system, published in 1998, and was superseded in 2009 by a further revision, the APG III system.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

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 It was superseded 6½ years later by the APG III system, published in October 2009.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

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

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.

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.

Notes and 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.