Biology:APG II system

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Short description: System of plant taxonomy


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April 2003 by the Angiosperm Phylogeny Group.[1] It was a revision of the first APG system, published in 1998, and was superseded in 2009 by a further revision, the APG III system.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 It was superseded 6½ years later by the APG III system, published in October 2009.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):

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



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