Taxonomy of the Orchidaceae

thumb|Illustration of "Orchideae" from [[Ernst Haeckel's Kunstformen der Natur]]

thumb|Artist's interpretation of orchid phylogeny.

The taxonomy of the Orchidaceae (orchid family) has evolved slowly during the last 250 years, starting with Carl Linnaeus who in 1753 recognized eight genera. De Jussieu recognized the Orchidaceae as a separate family in his Genera Plantarum in 1789. Olof Swartz recognized 25 genera in 1800. Louis Claude Richard provided us in 1817 with the descriptive terminology of the orchids. (See External links below). The next step was taken in 1830-1840 by John Lindley, who recognized four subfamilies. He is generally recognized as the father of orchid taxonomy. The next important step was taken by George Bentham with a new classification, recognizing subtribes for the first time. This classification was first presented in a paper that Bentham read to the Royal Society in 1881. Then it was published in 1883 in the final volume of Genera Plantarum. The next great contributors were Pfitzer (1887), Schlechter (1926), Mansfeld (1937), Dressler and Dodson (1960), Garay (1960, 1972), Vermeulen (1966), again Dressler (1981). and Burns-Balogh and Funk (1986). Dressler's 1993 book had considerable influence on later work.

Genera Orchidacearum was published in 6 volumes over 15 years, from 1999 to 2014. The first classification that was based on cladistic analysis of DNA data was published by Chase et alii in 2003.

An update to that classification was published by Chase et alii in 2015. This classification takes a different approach from Genera Orchidacearum, by consolidating many of the tribes and subtribes, and by recognizing very widely circumscribed genera. As of 2015, Orchidaceae was not yet covered in The Families and Genera of Vascular Plants, though most of the vascular plant families had been covered by that time.

The number of genera recognized in the family has varied from one classification to another. In Genera Orchidacearum, many genera were consolidated, reducing their number to 765, smaller than in any previous modern classification.

History

The following taxonomy follows largely the classification system of Robert Louis Dressler, an orchid specialist and adjunct curator at the Florida Museum of Natural History. This classification, published in 1981 in the book The Orchids: Natural History and Classification, was widely accepted by botanists and growers before the publication of Genera Orchidacearum. The initial scheme of 1981 was modified in 1986, twice in 1990, and then again in 1993. This comprehensive classification relies heavily on morphology, especially a few key characters, such as anther configuration and pollinarium structure. Consequently, many of the taxa are not monophyletic.

Cladistic analyses, especially those based on molecular data, provide a firmer basis for classification than intuition, and the certainty (or uncertainty) of conclusions can be quantified by measures of statistical support. While our understanding of orchid phylogeny has greatly improved in recent years, the elucidation of orchid relationships is still ongoing.

When Dressler published his classification in 1993, the relationships of orchids to other monocots was still unknown. Some of the first molecular phylogenetic studies of monocots resolved the Orchidaceae as sister to the astelioid clade of the order Asparagales, but this result never had strong statistical support. It is now known that Orchidaceae is the most basal clade in Asparagales, with the astelioid clade diverging next.

According to cladistic analyses based on morphological character states or on nucleotide sequences, the orchid family is a monophyletic group. The subfamilies recognized by Dressler, however, were not all monophyletic. Dressler's delimitation of subfamilies was contradicted by subsequent studies of mitochondrial, chloroplast, and nuclear DNA sequences. In 2003, a new phylogenetic classification divided Orchidaceae into five subfamilies: Apostasioideae, Vanilloideae, Cypripedioideae, Orchidoideae, and Epidendroideae. This result had only weak maximum parsimony jackknife support, but in a phylogenomic study in 2015, it received strong maximum likelihood bootstrap support.

Since 2006, phylogenies of two of the subfamilies, Vanilloideae and Epidendroideae have been published. Phylogenies of several tribes and subtribes have also been published. Compared to previous classifications, more of the tribes and subtribes of Dressler were monophyletic, but not all of them were supported by subsequent studies.

In the classification that was published in 2015, the authors expressed doubt about their division of the tribes Orchideae and Vandeae into subtribes. The placement of the genera Pachites, Holothrix, and Hederorkis is especially problematic. The monophyly of the subtribe Cranichidinae is also in doubt. These authors singled out the tribe Podochileae, as well as the subtribes Oncidiinae, Goodyerinae, and Angraecinae as being in special need of phylogenetic study. The basal epidendroids, especially the tribe Gastrodieae, remain poorly sampled in phylogenetic studies.

Alliance Vanda
Genera: Acampe, Adenoncos, Aerides, Amesiella, Arachnis, Ascocentrum, Ascoglossum, Biermannia, Bogoria, Brachypeza, Calymmanthera, Ceratocentron, Chamaeanthus, Chiloschista, Chroniochilus, Cleisocentron, Cleisomeria, Cleisostoma, Cleisostomopsis, Cottonia, Cymbilabia, Deceptor, Dimorphorchis, Diplocentrum, Diploprora, Dryadorchis, Drymoanthus, Dyakia, Eclecticus, Gastrochilus, Grosourdya, Holcoglossum, Hymenorchis, Jejewoodia, Kipandiorchis, Luisia, Macropodanthus, Micropera, Microsaccus, Mobilabium, Omoea, Ophioglossella, Papilionanthe, Paraphalaenopsis, Pelatantheria, Pennilabium, Peristeranthus, Phragmorchis, Plectorrhiza, Pomatocalpa, Porrorhachis, Pteroceras, Renanthera, Rhinerrhiza, Rhynchogyna, Rhynchostylis, Robiquetia, Saccolabiopsis, Saccolabium, Santotomasia, Sarcanthopsis, Sarcochilus, Sarcoglyphis, Sarcophyton, Schoenorchis, Seidenfadenia, Smithsonia, Smitinandia, Stereochilus, Taeniophyllum, Taprobanea, Thrixspermum, Trachoma, Trichoglottis, Tuberolabium, Uncifera, Vanda, and Vandopsis. Formerly Abdominea, Euanthe, Gunnarella, and Neofinetia.
Hybrids
Genera: × Aeridovanda, × Aranda, × Ascocenda, × Ascofinetia, × Asconopsis, × Christieara, × Opsistylis, × Perreiraara, × Renanstylis, × Renantanda, × Renanthopsis, × Rhynchovanda, × Vandaenopsis, × Vascostylis
Subtribe Angraecinae: about 400 species in 19 genera, tropical Africa and Madagascar.
Alliance Angraecum
Genera: Aeranthes, Angraecum, Bonniera, Calyptrochilum, Cryptopus, Jumellea, Lemurella, Lemurorchis, Neobathiea, Oeonia, Oeoniella, Sobennikoffia
Alliance Campylocentrum
Genera: Campylocentrum, Dendrophylax
Subtribe Polystachyinae (formerly part of the Epidendreae): about 220 species in four genera. They all show four pollinia. The lip often has mealy hairs called pseudopollen on the upper surface.
Genera: Hederorkis, Imerinaea, Neobenthamia, Polystachya

Tribe Maxillarieae

70 to 80 genera with about 1,000 species; most grow in tropical America as terrestrials or epiphytes, a few are myco-heterotrophs. Most show pseudobulbs, but a few have reedlike stems or thick underground stems. Blooms have four pollinia.

Subtribe Bifrenariinae: thin and pleated leaves.
Genera: Bifrenaria, Xylobium
Subtribe Corallorhizinae: all myco-heterotrophs
Genera: Aplectrum, Corallorhiza
Subtribe Dichaeinae
Genus: Dichaea
Subtribe Lycastinae: thin and pleated leaves.
Genera: Anguloa, Bifrenaria, Lycaste, Neomoorea, Ciripedium Rudolfiella, Teuscheria, Xylobium
Subtribe Maxillariinae: largest subtribe with nearly half of the tribe species. The leathery leaves are conduplicate, i.e. folded together lengthwise.
Genera: Chrysocycnis, Cyrtidium, Maxillaria, Mormolyca, Pityphyllum, Scuticaria, Sepalosaccus, Trigonidium
Subtribe: Ornithocephalinae
Genera: Ornithocephalus, Zygostates
Subtribe Stanhopeinae: about 200 species; epiphytes found in the Western Hemisphere.
Genera: Acineta, Braemia, Cirrhaea, Coryanthes, Embreea, Gongora, Horichia, Houlletia, Jennyella, Kegeliella, Lacaena, Lueddemannia, Paphinia, Polycycnis, Schlimia, Sievekingia, Soterosanthus, Stanhopea, Trevoria, Vasqueziella
Subtribe Coeliopsidinae
Genera: Coeliopsis, Lycomormium, Peristeria
Subtribe Telipogoninae
Genera: Dipterostele, Hofmeisterella, Stellilabium, Telipogon, Trichoceros
Subtribe Zygopetilinae: about 150 species.
Alliance Warrea
Genera: Otostylis, Warrea
Alliance Zygopetalum
Genera: Aganisia, Batemannia, Bollea, Cheiradenia, Chondrorhyncha, Cochleanthes, Colax, Pabstia, Promenaea, Zygopetalum
Alliance Bollea
Genera: Bollea, Chondrorhyncha, Cochleanthes, Huntleya, Kefersteinia, Pescatoria, Stenia
Alliance Vargasiella
Genus: Vargasiella
Alliance hybrids: of the 43 hybrids in this tribe, only × Angulocaste is displayed frequently.
Genera: Aitkenara, Bateostylis, Bollopetalum, Chondrobollea, Cochella, Cochlecaste, Cochlenia, Cochlepetalum, Downsara, Durutyara, Hamelwellsara, Huntleanthes, Kanzerara, Keferanthes, Lancebirkara, Otocolax, Otonisia, Palmerara, Rotorara, Zygocaste, Zygolum, Zygonisia, Zygostylis

Subfamily Orchidoideae

Tribe Diceratosteleae

Genus: Diceratostele

Tribe Codonorchideae

Genus: Codonorchis

Tribe Cranichideae

The former subfamily Spiranthoideae is now embedded in the clade Orchidoideae as the tribe Cranichideae (Dressler, 1993). It includes 95 genera and about 1100 species. Species of this polyphyletic tribe occur in all continents (except Antarctica), but mainly in North and South America and tropical Asia. All subtribes are monophyletic.

Subtribe Cranichidinae: occurring in the Neotropics
Genera: Altensteinia, Baskervilla, Cranichis, Exalaria, Fuertesiella, Myrosmodes, Nothostele, Ponthieva, Pseudocentrum, Pseudocranichis, Pterichis, Solenocentrum
Subtribe Prescottiinae: occurs in the Neotropics
Genera: Aa, Gomphichis, Porphyrostachys, Prescottia, Stenoptera
Subtribe Galeottiellinae
Genus: Galeottiella
Subtribe Goodyerinae: 37 genera, about 630 species in Africa, the Americas and Asia.
Genera: Aenhenrya, Anoectochilus, Aspidogyne, Chamaegastrodia, Cheirostylis, Cystorchis, Danhatchia, Dassinia, Erythrodes, Eurycentrum, Gonatostylis, Goodyera, Halleorchis, Herpysma, Hetaeria, Hylophila, Kreodanthus, Kuhlhasseltia, Lepidogyne, Lageophila, Ludisia, Macodes, Meliorchis (extinct), Microchilus, Myrmechis, Odontochilus, Orchipedum, Pachyplectron, Papuaea, Platylepis, Platythelys, Rhamphorhynchus, Rhomboda, Stephanothelys, Vrydagzynea, Zeuxine
Subtribe Manniellinae: tropical Africa
Genus: Manniella
Subtribe Pterostylidinae
Genera: Achlydosa, Pterostylis

upright|thumb|right|Nodding ladies' tresses ([[Spiranthes cernua)]]

Subtribe Spiranthinae: about 30 genera; largely terrestrial; widespread, but absent in sub-Saharan Africa; fascicled roots, dorsal erect anther, inconspicuous staminodia, resupinate flowers.
Genera: Aracamunia, Aulosepalum, Beloglottis, Brachystele, Buchtienia, Coccineorchis, Cotylolabium, Cybebus, Degranvillea, Deiregyne, Dichromanthus, Discyphus, Eltroplectris, Eurystyles, Funkiella, Hapalorchis, Helonoma, Kionophyton, Lankesterella, Lyroglossa, Mesadenella, Mesadenus, Microthelys, Odontorrhynchus, Pelexia, Physogyne, Pseudogoodyera, Pteroglossa, Sacoila, Sarcoglottis, Sauroglossum, Schiedeella, Skeptrostachys, Spiranthes, Stalkya, Svenkoeltzia, Thelyschista, Veyretia, Wallnoeferia
Subtribe Stenorrhynchidinae
Genus: Stenorrhynchos
Subtribe Cyclopogoninae
Genus: Cyclopogon

Tribe Diseae

Subtribe Brownleeinae
Genus: Brownleea
Subtribe Coryciinae
Genera: Ceratandra, Corycium, Disperis, Evotella, Pterygodium
Subtribe Disinae
Genera: Disa, Schizodium
Subtribe Huttonaeinae
Genus: Huttonaea
Subtribe Satyriinae
Genera: Pachites, Satyrium

Tribe Diurideae

About 550 species in 39 genera; mainly Australasia.

Subtribe Acianthinae
Genera: Acianthus, Corybas, Cyrtostylis, Stigmatodactylus, Townsonia
Subtribe Caladeniinae
Genera: Adenochilus, Aporostylis, Caladenia, Cyanicula, Elythranthera, Ericksonella, Eriochilus, Glossodia, Leptoceras, Pheladenia, Praecoxanthus
Subtribe Chloraeinae: From South America and New Caledonia (Megastylis)
Genera: Bipinnula, Chloraea, Gavilea, Geoblasta, Megastylis
Subtribe Cryptostylidinae
Genera: Coilochilus, Cryptostylis
Subtribe Diuridinae
Genera: Diuris, Orthoceras
Subtribe Drakaeinae
Genera: Arthrochilus, Caleana, Chiloglottis, Drakaea, Myrmechila, Spiculaea
Subtribe Megastylidinae
Genera: Burnettia, Leporella, Lyperanthus, Megastylis, Pyrorchis, Rimacola, Waireia
Subtribe Prasophyllinae
Genera: Genoplesium, Microtis, Prasophyllum
Subtribe Pterostylidinae
Subtribe Thelymitrinae
Genera: Calochilus, Epiblema, Thelymitra

Tribe Orchideae

This is the largest tribe, containing more than 1,700 species. It has been divided into two subtribes, Orchidinae and Habenariinae. However, the generic boundaries are unclear, and phylogenetic studies show that many genera are paraphyletic or even polyphyletic, so a clear assignment of genera to subtribes is currently not possible.

upright|thumb|Prairie white fringed orchid ([[Platanthera leucophaea)]]

Genera: Aceratorchis, Amerorchis, Anacamptis, Bartholina, Benthamia, Bonatea, Brachycorythis, Centrostigma, Chamorchis, Chondradenia, Cynorchis, Dactylorhiza, Diphylax, Diplomeris, Dracomonticola, Galearis, Gennaria, Gymnadenia, Habenaria, Hemipilia, Herminium, Himantoglossum, Holothrix, Megalorchis, Neobolusia, Neotinea, Oligophyton, Ophrys, Orchis, Pecteilis, Peristylus, Physoceras, Platanthera, Platycoryne, Ponerorchis, Pseudorchis, Roeperocharis, Schizochilus, Serapias, Stenoglottis, Steveniella, Symphyosepalum, Thulinia, Traunsteinera, Tylostigma, Veyretella

Subfamily Vanilloideae

Tribe Pogonieae

Genera: Cleistes, Duckeella, Isotria, Pogonia, Pogoniopsis

Tribe Vanilleae

Genera: Clematepistephium, Cyrtosia, Dictyophyllaria, Epistephium, Eriaxis, Erythrorchis, Galeola, Lecanorchis, Pseudovanilla, Vanilla

References

Bibliography

WCSP (2012). World Checklist of Selected Plant Families. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; WCSP Online.
Chase, M. W. 2005. Classification of Orchidaceae in the age of DNA data. Curtis's Bot. Mag. 22(1): 2–7.
History of the taxonomy of orchids
Orchid Tree: a phylogeny of epiphytes (mostly) on the Tree of Life

External links

page 939 volume 2 Species Plantarum first edition (1753) Titles by Carl von Linné (1707-1778) Authors Biodiversity Heritage Library
Orchideae page 64 View Book Antonii Laurentii de Jussieu Genera plantarum Jussieu, Antoine Laurent de, 1748-1836 Authors BHL
View Book De Orchideis Europaeis annotationes Titles by Louis Claude Richard authors BHL
View Book The Genera and Species of Orchidaceous Plants Titles BHL
page 288 volume 18 The Journal of the Linnean Society. Botany titles BHL
orchids, page 460 View Book Genera Plantarum (Bentham & Hooker, 1883) volume 3, part 2 titles BHL
Afhandling om Orchidernes Slägter och deras Systematiska indelning GDZ
The Orchids: Natural History and Classification (1981)
rbcL phylogeny of Orchidaceae (1999)
DNA data and Orchidaceae Systematics: A new Phylogenetic Classification by Mark W. Chase, Kenneth M.Cameron, Russell L. Barrett, John V. Freudenstein (2003)
An updated classification of Orchidaceae (2015) Botanical Journal of the Linnean Society Wiley Online Library
Orchidaceae angiosperms Browse The Plant List
APG III
genus list Orchidaceae Asparagales Trees APweb Missouri Botanical Garden
Useful links
Taxonomy (in Portuguese)
Native Orchids of Provence (France) French & English