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APG III system

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See also: Angiosperm Phylogeny Group

The APG III system (Angiosperm Phylogeny Group III system) of plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy that was published in 2009 by the Angiosperm Phylogeny Group, 6½ years after its predecessor, the APG II system was published.[1][2][3]

In October 2009, members of the Linnean Society proposed an accompanying formal phylogenetic classification of all land plants, compatible with the APG III classification.[4] This was needed because botanists and phycologists often disagree on the taxonomic rank to which groups are assigned.

The APG III system recognized all of the 45 orders of the previous system, as well as 14 new ones. The order Ceratophyllales was erroneously marked as a new order, but it had been recognized in both of the previous APG systems. The newly recognized orders were:

Amborellales, Nymphaeales, Chloranthales, Petrosaviales, Trochodendrales, Buxales, Vitales, Zygophyllales, Picramniales, Huerteales, Berberidopsidales, Escalloniales, Bruniales, and Paracryphiales.

The designation of alternative "bracketed families" was abandoned in APG III, because its inclusion in the previous system had been unpopular. APG III recognized 415 families, 42 fewer than in the previous system. Forty-four of the 55 "bracketed families" were discontinued, and 18 other families were discontinued as well.

The discontinued bracketed families were:

Illiciaceae, Alliaceae, Agapanthaceae, Agavaceae, Aphyllanthaceae, Hesperocallidaceae, Hyacinthaceae, Laxmanniaceae, Ruscaceae, Themidaceae, Asphodelaceae, Hemerocallidaceae, Kingdoniaceae, Fumariaceae, Pteridophyllaceae, Didymelaceae, Tetracentraceae, Pterostemonaceae, Hypseocharitaceae, Francoaceae, Memecylaceae, Lepuropetalaceae, Rhoipteleaceae, Medusagynaceae, Quiinaceae, Malesherbiaceae, Turneraceae, Bretschneideraceae, Diegodendraceae, Cochlospermaceae, Peganaceae, Tetradiclidaceae, Nyssaceae, Ternstroemiaceae, Pellicieraceae, Aucubaceae, Donatiaceae, Lobeliaceae, Desfontainiaceae, Diervillaceae, Dipsacaceae, Linnaeaceae, Morinaceae, and Valerianaceae.

The other discontinued families were:

Limnocharitaceae, Luzuriagaceae, Sparganiaceae, Ledocarpaceae, Heteropyxidaceae, Psiloxylaceae, Oliniaceae, Rhynchocalycaceae, Parnassiaceae, Maesaceae, Myrsinaceae, Theophrastaceae, Eremosynaceae, Polyosmaceae, Tribelaceae, Aralidiaceae, Mackinlayaceae, and Melanophyllaceae.

20 families were accepted in the APG III system which had not been in the previous system, and a few families were moved to a different position. The newly recognized families are:

Petermanniaceae, Schoepfiaceae, Limeaceae, Lophiocarpaceae, Montiaceae, Talinaceae, Anacampserotaceae, Centroplacaceae, Calophyllaceae, Guamatelaceae, Gerrardinaceae, Dipentodontaceae, Capparidaceae, Cleomaceae, Cytinaceae, Mitrastemonaceae, Metteniusaceae, Linderniaceae, Thomandersiaceae, and Quintiniaceae.

The number of families not placed in any order was reduced from 39 to 10. Apodanthaceae and Cynomoriaceae were placed among the angiosperms, incertae sedis, that is, not in any group within the angiosperms. Eight other families were placed incertae sedis in various supra-ordinal groups within the angiosperms. The unplaced families were:

Apodanthaceae, Cynomoriaceae, Dasypogonaceae, Sabiaceae, Dilleniaceae, Icacinaceae, Metteniusaceae, Oncothecaceae, Vahliaceae, and Boraginaceae.

The circumscription of the family Icacinaceae remains especially doubtful. Apodytes, Emmotum, Cassinopsis, and a few other genera were provisionally retained within it until further studies can determine whether they properly belong there.

Three genera (Gumillea, Nicobariodendron, and Petenaea) were placed within the angiosperms incertae sedis. Gumillea had been unplaced in APG II. Nicobariodendron and Petenaea were newly added to the list.

The classification is shown below in two versions. The short version goes to the level of orders and of families unplaced in an order. The detailed version shows all the families. Orders at the same level in the classification are arranged alphabetically. Note that orders may not contain the same families as in earlier versions of the APG system (APG system, APG II system). Further detail on relationships can be seen in the phylogenetic tree below.

Short version

Detailed version (with all families)

Legend:

* = new family placement;
† = newly recognized order for the APG system;
§ = new family circumscription described in the text;
$ = families that represent the broader circumscription of options available in APG II and favoured here;
$$ = families that were in square brackets in APG II, the narrower circumscriptions favoured here.

Angiosperms

Magnoliids

Monocots

Commelinids

Probable sister of eudicots

Eudicots

Core eudicots

Rosids

Eurosids I

Eurosids II

Asterids

Euasterids I

Euasterids II

Taxa of uncertain position

Phylogeny

The APG III system was based on a phylogenetic tree for the angiosperms which included all of the 59 orders and 4 of the unplaced families. The systematic positions of the other 6 unplaced families was so uncertain that they could not be placed in any of the polytomies in the tree. They are shown in the classification table entitled "Detailed version" above.

The phylogenetic tree shown below was published with the APG III system,[1] but without some of the labels that are added here.

angiosperms 

Amborellales

Nymphaeales

Campanulids (continued)

*campanulids 

Subfamilies replacing discontinued families

A number of subfamilies have been proposed to replace some of the families which were optional (i.e. bracketed) in APG II, but have been discontinued in APG III.[5] These are shown in the table below.

Subfamilies replacing APG II bracketed families
APG II bracketed family APG III family: subfamily
Agapanthaceae Amaryllidaceae: Agapanthoideae
Agavaceae Asparagaceae: Agavoideae
Alliaceae Amaryllidaceae: Allioideae
Amaryllidaceae Amaryllidaceae: Amaryllidoideae
Aphyllanthaceae Asparagaceae: Aphyllanthoideae
Asparagaceae Asparagaceae: Asparagoideae
Asphodelaceae Xanthorrhoeaceae: Asphodeloideae
Hemerocallidaceae Xanthorrhoeaceae: Hemerocallidoideae
Hesperocallidaceae Asparagaceae: Agavoideae
Hyacinthaceae Asparagaceae: Scilloideae
Laxmanniaceae Asparagaceae: Lomandroideae
Ruscaceae Asparagaceae: Nolinoideae
Themidaceae Asparagaceae: Brodiaeoideae
Xanthorrhoeaceae Xanthorrhoeaceae: Xanthorrhoeoideae

References

  1. ^ a b Angiosperm Phylogeny Group (2009), "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III", Botanical Journal of the Linnean Society, 161 (2): 105–121, doi:10.1111/j.1095-8339.2009.00996.x, retrieved 2010–12–10 {{citation}}: Check date values in: |accessdate= (help)
  2. ^ As easy as APG III - Scientists revise the system of classifying flowering plants, The Linnean Society of London, 2009-10-08, retrieved 2009-10-29
  3. ^ APG III tidies up plant family tree, Horticulture Week, 2009-10-08, retrieved 2009-10-29
  4. ^ Chase, Mark W.; Reveal, James L. (2009), "A phylogenetic classification of the land plants to accompany APG III", Botanical Journal of the Linnean Society, 161 (2): 122–127, doi:10.1111/j.1095-8339.2009.01002.x {{citation}}: Unknown parameter |lastauthoramp= ignored (|name-list-style= suggested) (help)
  5. ^ Chase, M.W.; Reveal, J.L.; Fay, M.F. (2009), "A subfamilial classification for the expanded asparagalean families Amaryllidaceae, Asparagaceae and Xanthorrhoeaceae", Botanical Journal of the Linnean Society, 161 (2): 132–136, doi:10.1111/j.1095-8339.2009.00999.x {{citation}}: Unknown parameter |lastauthoramp= ignored (|name-list-style= suggested) (help)

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