APG III system

The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a further revision, the APG IV system.[1][2][3]

See also: Angiosperm Phylogeny Group

Along with the publication outlining the new system, there were two accompanying publications in the same issue of the Botanical Journal of the Linnean Society. The first, by Chase & Reveal, was a formal phylogenetic classification of all land plants (embryophytes), compatible with the APG III classification. As the APG have chosen to eschew ranks above order, this paper was meant to fit the system into the existing Linnaean hierarchy for those that prefer such a classification. The result was that all land plants were placed in the class Equisetopsida, which was then divided into 16 subclasses and a multitude of superorders.[4] The second, by Haston et al., was a linear sequence of families following the APG III system (LAPG III).

This provided a numbered list to the 413 families of APG III. A linear sequence is of particular use to herbarium curators and those working on floristic works wishing to arrange their taxa according to APG III.[5]

Organization

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, as 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 413 families, 43 fewer than in the previous system. Forty-four of the 55 "bracketed families" were discontinued, and 20 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, Ixerbaceae, Ledocarpaceae, Heteropyxidaceae, Psiloxylaceae, Oliniaceae, Rhynchocalycaceae, Parnassiaceae, Maesaceae, Myrsinaceae, Theophrastaceae, Eremosynaceae, Polyosmaceae, Tribelaceae, Sphenostemonaceae, Aralidiaceae, Mackinlayaceae, and Melanophyllaceae.

21 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:

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

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 families not placed in any order were:

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

The paragraph below shows the number of families in each order and the placement of those families that were not included in any order. These figures were produced by simply counting the families in the text of the paper that established APG III.[1]

ORDERS: Amborellales (1), Nymphaeales (3), Austrobaileyales (3), Chloranthales (1), Canellales (2), Piperales (5), Magnoliales (6), Laurales (7), Acorales (1), Alismatales (13), Petrosaviales (1), Dioscoreales (3), Pandanales (5), Liliales (10), Asparagales (14), Arecales (1), Poales (16), Commelinales (5), Zingiberales (8), Ceratophyllales (1), Ranunculales (7), Proteales (3), Trochodendrales (1), Buxales (2), Gunnerales (2), Saxifragales (14), Vitales (1), Zygophyllales (2), Celastrales (2), Oxalidales (7), Malpighiales (35), Fabales (4), Rosales (9), Fagales (7), Cucurbitales (7), Geraniales (3), Myrtales (9), Crossosomatales (7), Picramniales (1), Sapindales (9), Huerteales (3), Brassicales (17), Malvales (10), Berberidopsidales (2), Santalales (7), Caryophyllales (34), Cornales (6), Ericales (22), Garryales (2), Gentianales (5), Solanales (5), Lamiales (23), Aquifoliales (5), Asterales (11), Escalloniales (1), Bruniales (2), Apiales (7), Paracryphiales (1), Dipsacales (2).

SUPRA-ORDINAL GROUPS: commelinids (1), basal eudicots (1), Pentapetalae (1), lamiids incertae sedis (3), core lamiids (2), angiosperms incertae sedis (2).

The circumscription of the family Icacinaceae remains especially doubtful. Apodytes and its close relative, Rhaphiostylis, as well as 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 latter was later placed into its own family Petenaeaceae in the order Huerteales[6][7]

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

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

Fabids (eurosids I)

malvids (eurosids II)

Asterids

lamiids (euasterids I)

campanulids (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, 4 in Euasterids I and 2 in Taxa of uncertain position.

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

 
 
 

Austrobaileyales

 
 
 
 

Chloranthales

 
magnoliids 
 
 

Canellales

 
 

Piperales

 
 
 
 

Magnoliales

 
 

Laurales

 
 
 
 
 
monocots 
 

Acorales

 
 
 

Alismatales

 
 
 

Petrosaviales

 
 
 
 

Dioscoreales

 
 

Pandanales

 
 
 
 

Liliales

 
 
 

Asparagales

 
commelinids 
 

Dasypogonaceae

 
 

Arecales

 
 

Poales

 
 
 

Commelinales

 
 

Zingiberales

 
 
 
 
 
 
 
 
 
 
 

Ceratophyllales

 
eudicots 
 

Ranunculales

 
 
 

Sabiaceae

 
 

Proteales

 
 
 

Trochodendrales

 
 

Buxales

 
core eudicots 
 

Gunnerales

 
 
 

Dilleniaceae

 
 
 

Saxifragales

 
rosids 
 

Vitales

 
eurosids 
fabids 
 

Zygophyllales

 
 
 
 

Celastrales

 
 
 

Oxalidales

 
 

Malpighiales

 
 
 
 
 

Fabales

 
 
 

Rosales

 
 
 

Fagales

 
 

Cucurbitales

 
 
 
 
 
 
malvids 
 
 

Geraniales

 
 

Myrtales

 
 
 
 

Crossosomatales

 
 
 

Picramniales

 
 
 

Sapindales

 
 
 

Huerteales

 
 
 

Brassicales

 
 

Malvales

 
 
 
 
 
 
 
 
 
 
 
 

Berberidopsidales

 
 
 

Santalales

 
 
 

Caryophyllales

 
asterids 
 

Cornales

 
 
 

Ericales

 
euasterids 
lamiids 
 

Garryales

 
 
 

Boraginaceae

 
 

Gentianales

 
 
 

Solanales

 
 

Lamiales

 
 
 
 
campanulids 
 

Aquifoliales

 
 
 

Asterales

 
 

Escalloniales

 
 
 

Bruniales

 
 
 

Apiales

 
 
 

Paracryphiales

 
 

Dipsacales

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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.[8] These are shown in the table below.

Subfamilies replacing APG II bracketed families
APG II bracketed familyAPG III family: subfamily
AgapanthaceaeAmaryllidaceae: Agapanthoideae
AgavaceaeAsparagaceae: Agavoideae
AlliaceaeAmaryllidaceae: Allioideae
AmaryllidaceaeAmaryllidaceae: Amaryllidoideae
AphyllanthaceaeAsparagaceae: Aphyllanthoideae
AsparagaceaeAsparagaceae: Asparagoideae
AsphodelaceaeXanthorrhoeaceae: Asphodeloideae
HemerocallidaceaeXanthorrhoeaceae: Hemerocallidoideae
HesperocallidaceaeAsparagaceae: Agavoideae
HyacinthaceaeAsparagaceae: Scilloideae
LaxmanniaceaeAsparagaceae: Lomandroideae
RuscaceaeAsparagaceae: Nolinoideae
ThemidaceaeAsparagaceae: Brodiaeoideae
XanthorrhoeaceaeXanthorrhoeaceae: Xanthorrhoeoideae
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References
  1. 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, archived from the original on 2017-05-25, retrieved 2010-12-10
  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
  5. Haston, E., Richardson, J.E., Stevens, P.F., Chase, M.W., Harris, D.J. (2009) The Linear Angiosperm Phylogeny Group (LAPG) III: a linear sequence of the families in APG III. Botanical Journal of the Linnean Society 161, 128–131.
  6. Christenhusz, M. J. M., M. F. Fay, J. J. Clarkson, P. Gasson, J. Morales Can, J. B. Jimenez Barrios & M. W. Chase (2010). Petenaeaceae, a new angiosperm family in Huerteales with a distant relationship to Gerrardina (Gerrardinaceae), Botanical Journal of the Linnean Society 164: 16-25. http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8339.2010.01074.x/abstract
  7. Christenhusz, M. J. M., M. W. Chase, & M.F.Fay (2011). Preface to "Linear sequence, classification, synonymy, and bibliography of vascular plants: Lycophytes, ferns, gymnosperms and angiosperms", Phytotaxa 19: 4–6. http://www.mapress.com/phytotaxa/content/2011/f/pt00019p006.pdf
  8. 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

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, Ventenat, Batsch and Grisebach.

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