Pteridophyte Phylogeny Group
The Pteridophyte Phylogeny Group (PPG) is an informal international group of systematic botanists who collaborate to establish a consensus on the classification of pteridophytes (lycophytes and ferns) that reflects knowledge about plant relationships discovered through phylogenetic studies. In 2016, the group published a classification for extant pteridophytes, termed "PPG I". The paper had 94 authors (26 principal and 68 additional).[1]
PPG I
A first classification, PPG I, was produced in 2016, covering only extant (living) pteridophytes. The classification was rank-based, using the ranks of class, subclass, order, suborder, family, subfamily and genus.[1]
Phylogeny
The classification was based on a consensus phylogeny, shown below to the level of order.[1]
tracheophytes
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The very large order Polypodiales was divided into two suborders, as well as families not placed in a suborder:[1]
Polypodiales |
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Classification to subfamily level
To the level of subfamily, the PPG I classification is as follows.[1]
- Class Lycopodiopsida Bartl. (3 orders, 3 families, 18 genera)
- Order LycopodialesDC. ex Bercht. & J.Presl (1 family, 16 genera)
- Family Lycopodiaceae P.Beauv. (16 genera)
- Subfamily Lycopodielloideae W.H.Wagner & Beitel ex B.Øllg. (4 genera)
- Subfamily Lycopodioideae W.H.Wagner & Beitel ex B. Øllg. (9 genera)
- Subfamily Huperzioideae W.H.Wagner & Beitel ex B. Øllg. (3 genera)
- Order IsoëtalesPrantl (1 family, 1 genus)
- Family IsoëtaceaeDumort. (1 genus)
- Family
- Order SelaginellalesPrantl (1 family, 1 genus)
- Family SelaginellaceaeWillk (1 genus)
- Family
- Order
- Class PolypodiopsidaCronquist, Takht. & W.Zimm. (11 orders, 48 families, 319 genera)
- Subclass Equisetidae Warm. (1 order, 1 family, 1 genus)
- Order Equisetales DC. ex Bercht. & J.Presl (1 family, 1 genus)
- Family Equisetaceae Michx. ex DC (1 genus)
- Subclass Ophioglossidae Klinge (2 orders, 2 families, 12 genera)
- Order PsilotalesPrant (1 family, 2 genera)
- Family Psilotaceae J.W.Griff. & Henfr. (2 genera)
- Order OphioglossalesLink (1 family, 10 genera)
- Family Ophioglossaceae Martinov (10 genera)
- Subfamily HelminthostachyoideaeC.Presl (1 genus)
- Subfamily MankyuoideaeJ.R.Grant & B.Dauphin (1 genus)
- Subfamily OphioglossoideaeC.Presl (4 genera)
- Subfamily BotrychioideaeC.Presl (4 genera)
- Subfamily
- Order
- Subclass MarattiidaeKlinge (1 order, 1 family, 6 genera)
- Order MarattialesLink (1 family, 6 genera)
- Family Marattiaceae Kaulf (6 genera)
- Order
- Subclass PolypodiidaeCronquist, Takht. & W.Zimm. (7 orders, 44 families, 300 genera)
- Order OsmundalesLink (1 family, 6 genera)
- Family Osmundaceae Martinov (6 genera)
- Order HymenophyllalesA.B.Frank (1 family, 9 genera)
- Family Hymenophyllaceae Mart (9 genera)
- Subfamily TrichomanoideaeC.Presl (8 genera)
- Subfamily HymenophylloideaeBurnett (1 genus)
- Subfamily
- Order Gleicheniales Schimp (3 families, 10 genera)
- Family Matoniaceae C.Pres (2 genera)
- Family Dipteridaceae Seward & E.Dale (2 genera)
- Family Gleicheniaceae C.Presl (6 genera)
- Order Schizaeales Schimp. (3 families, 4 genera)
- Family LygodiaceaeM.Roem (1 genus)
- Family Schizaeaceae Kaulf (2 genera)
- Family AnemiaceaeLink (1 genus)
- Family
- Order Salviniales Link (2 families, 5 genera)
- Family Salviniaceae Martinov (2 genera)
- Family Marsileaceae Mirb. (3 genera)
- Order Cyatheales A.B.Frank (8 families, 13 genera)
- Family ThyrsopteridaceaeC.Presl (1 genus)
- Family Loxsomataceae C.Presl (2 genera)
- Family CulcitaceaePic.Serm (1 genus)
- Family PlagiogyriaceaeBowe (1 genus)
- Family CibotiaceaeKoral (1 genus)
- Family MetaxyaceaePic.Serm. (1 genus)
- Family Dicksoniaceae M.R.Schomb. (3 genera)
- Family Cyatheaceae Kaulf. (3 genera)
- Family
- Order Polypodiales Link (26 families, 253 genera)
- Suborder SaccolomatineaeHovenkamp (1 family, 1 genus)
- Family Saccolomataceae Doweld (1 genus)
- Suborder Lindsaeineae Lehtonen & Tuomist (3 families, 9 genera)
- Family CystodiaceaeJ.R.Croft (1 genus)
- Family LonchitidaceaeDoweld (1 genus)
- Family Lindsaeaceae C.Presl ex M.R.Schomb. (7 genera)
- Family
- Suborder PteridineaeJ.Prado & Schuettp (1 family, 53 genera)
- Family Pteridaceae E.D.M.Kirchn. (53 genera)
- Subfamily Parkerioideae Burnett (2 genera)
- Subfamily Cryptogrammoideae S.Lindsay (3 genera)
- Subfamily Pteridoideae Link (13 genera)
- Subfamily Vittarioideae Link (12 genera)
- Subfamily Cheilanthoideae Horvat (23 genera)
- Suborder DennstaedtiineaeSchwartsb. & Hovenkamp (1 family, 10 genera)
- Family Dennstaedtiaceae Lotsy (10 genera)
- Suborder Aspleniineae H.Schneid. & C.J.Rothf (11 families, 72 genera)
- Family Cystopteridaceae Shmakov (3 genera)
- Family RhachidosoraceaeX.C.Zhang (1 genus)
- Family Diplaziopsidaceae X.C.Zhang & Christenh. (2 genera)
- Family DesmophlebiaceaeMynssen (1 genus)
- Family HemidictyaceaeChristenh. & H.Schneid. (1 genus)
- Family Aspleniaceae Newman (2 genera)
- Family Woodsiaceae Herter (1 genus)
- Family Onocleaceae Pic.Serm. (4 genera)
- Family Blechnaceae Newman (24 genera)
- Subfamily Stenochlaenoideae(Ching) J.P.Roux (3 genera)
- Subfamily WoodwardioideaeGasper (3 genera)
- Subfamily BlechnoideaeGasper, V.A.O.Dittrich & Salino (18 genera)
- Subfamily
- Family Athyriaceae Alston (3 genera)
- Family Thelypteridaceae Ching ex Pic.Serm. (30 genera)
- Subfamily PhegopteridoideaeSalino, A.R.Sm. & T.E.Almeid (3 genera)
- Subfamily ThelypteridoideaeC.F.Reed (27 genera)
- Subfamily
- Suborder Polypodiineae Dumort. (9 families, 108 genera)
- Family DidymochlaenaceaeChing ex Li Bing Zhang & Liang Zhang (1 genus)
- Family Hypodematiaceae Ching (2 genera)
- Family Dryopteridaceae Herter (26 genera)
- Subfamily Polybotryoideae H.M.Liu & X.C.Zhang (7 genera)
- Subfamily Elaphoglossoideae (Pic.Serm.) Crabbe, Jermy & Mickel (11 genera)
- Subfamily DryopteridoideaeLink (6 genera)
- 2 genera not assigned to a subfamily
- Family NephrolepidaceaePic.Serm. (1 genus)
- Family Lomariopsidaceae Alston (4 genera)
- Family Tectariaceae Panigrahi (7 genera)
- Family OleandraceaeChing ex Pic.Serm. (1 genus)
- Family DavalliaceaeM.R.Schomb. (1 genus)
- Family Polypodiaceae J.Presl & C.Presl (65 genera)
- Subfamily Loxogrammoideae H.Schneid. (2 genera)
- Subfamily Platycerioideae B.K.Nayar (2 genera)
- Subfamily Drynarioideae Crabbe, Jermy & Mickel (6 genera)
- Subfamily Microsoroideae B.K.Nayar (12 genera)
- Subfamily Polypodioideae Sweet (9 genera)
- Subfamily Grammitidoideae Parris & Sundue (33 genera)
- 1 genus not assigned to a subfamily
- Family
- Suborder
- Order
Number of genera
The number of genera used in PPG I has proved controversial. PPG I uses 18 lycophyte and 319 fern genera.[1] The earlier system put forward by Smith et al. (2006) had suggested a range of 274 to 312 genera for ferns alone.[2] By contrast, the system of Christenhusz and Chase (2014) used 5 lycophyte and about 212 fern genera.[3] The number of fern genera was further reduced to 207 in a subsequent publication.[4]
The number of genera used in each of these two approaches has been defended by their proponents. Defending PPG I, Schuettpelz et al. (2018) argue that the larger number of genera is a result of "the gradual accumulation of new collections and new data" and hence "a greater appreciation of fern diversity and [..] an improved ability to distinguish taxa". They also argue that the number of species per genus in the PPG I system is already higher than in other groups of organisms (about 33 species per genus for ferns as opposed to about 22 species per genus for angiosperms) and that reducing the number of genera as Christenhusz and Chase propose yields the excessive number of about 50 species per genus for ferns.[5] In response, Christenhusz and Chase (2018) argue that the excessive splitting of genera destabilises the usage of names and will lead to greater instability in future, and that the highly split genera have few if any characters that can be used to recognize them, making identification difficult, even to generic level. They further argue that comparing numbers of species per genus in different groups is "fundamentally meaningless".[4]
See also
References
- ^
- JSTOR 25065646
- PMID 24532607
- ^ doi:10.12705/673.2
- doi:10.12705/673.1