Genera Orchidacearum was published in 6 volumes over 15 years, from 1999 to 2014. It covers all of the known orchids, including a description of each genus. It reflects the considerable progress in orchid taxonomy that had been made since Dressler published his classification in 1993. In the 1990s, orchid taxonomy began to be influenced by molecular phylogenetics based on DNA sequences. The first molecular phylogenetic study to include a substantial sample of orchids was published in 1999. The first classification that was based on cladistic analysis of DNAdata was published by Chaseet 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. In 2015, Chase et alii merged even more genera, reducing their number to 736.
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 orderAsparagales, but this result never had strong statistical support. It is now known that Orchidaceae is the most basalclade 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 nuclearDNA sequences. In 2003, a new phylogenetic classification divided Orchidaceae into five subfamilies: Apostasioideae, Vanilloideae, Cypripedioideae, Orchidoideae, and Epidendroideae. These five subfamilies were all strongly supported as monophyletic groups in subsequent studies.
In 2003, the position of Vanilloideae remained equivocal. The subfamilies Orchidoideae and Epidendroideae clearly formed a monophyletic group and Dressler believed that their closest relative was Vanilloideae. In 2006, a study based on the plastidgenesrbcL and atpB found the closest relative of this pair to be Cypripedioideae, rather than Vanilloideae. This result had only weak maximum parsimonyjackknife support, but in a phylogenomic study in 2015, it received strong maximum likelihoodbootstrap 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.
The orchid family (Orchidaceae) is subdivided into five subfamilies, and then into tribes and subtribes. Groups of closely related genera are sometimes referred to informally as alliances. An alliance is a group of taxa, at any taxonomic rank, but usually at the rank of genus or species, that are thought to be closely related. Alliances are designated provisionally and are not recognized in the ICNAFP.
The subtribes are formally divided into genera. Some of the genera are divided into subgenera, and some of the subgenera are divided into sections. All of the genera contain at least one species. A special nomenclature is used to name hybrids between different species.
About 150 species and about a dozen new genera were described each year from 2000 to 2015.
According to Dressler, there are 5 subfamilies, 22 tribes, 70 subtribes, and about 850 genera of orchids. When he published his classification, only about 20,000 species of orchids were known. Several thousand have been described since then.
A distinction between monandrous flowers and others is especially important in the classification of orchids. A monandrous flower is one that has only a single stamen. The flowers are monandrous in the subfamilies Vanilloideae, Orchidoideae, and Epidendroideae. Like many others before him, Dressler believed that the monandrous orchids form a monophyletic group. It is now known that monandry arose twice in the orchids, once in Vanilloideae, and again in the common ancestor of Orchidoideae and Epidendroideae. The other subfamilies, Apostasioideae and Cypripedioideae, have either three stamens or two stamens and a staminode.
The subfamily Apostasioideae belongs to the orchid family (Orchidaceae). All well-sampled molecular phylogenetic studies have produced strong bootstrap support for its position as sister to a clade consisting of the other orchid subfamilies. Bootstraping is a method of resampling for quantifying the statistical support for nodes in a phylogenetic tree (= a treelike diagram showing the evolutionarydiversification of organisms).
The apostasioid orchids are the most primitive orchids, with only two genera. Neuwiedia has three fertile, abaxial (= facing away from the stem) anthers, while Apostasia has two fertile abaxial anthers and a filamentous staminode (= a sterile stamen). Plants with mealy or paste-like pollen, which ordinarily are not aggregated into pellets, called pollinia, with two or three fertile long anthers, leaves with sheathing bases, elongated staminode and labellum similar to the petals.
These primitive features make them, according to some authorities, not true orchids but rather ancestors of modern orchids. However, more recent studies indicate that many of their differences with the other orchids were not inherited from a common ancestor with orchids, but arose within the stem group of apostasioid orchids.
This is the largest subfamily, comprising more than 10,000 species in about 90 to 100 genera. Most are tropicalepiphytes (usually with pseudobulbs), but some are terrestrials and even a few are myco-heterotrophs. All show a unique development of the single anther: it is incumbent, meaning that it forms a right angle with the column axis or pointed backward in many genera. Most have hard pollinia, i.e. a mass of waxy pollen or of coherent pollen grains; pollinia with caudicle and viscidium or without; stigma entire or 3-lobed; rostellum present; 1-locularovary; leaves: distichous or spiraling
Formerly called Vandoideae, this is the second largest subfamily with over 300 genera in more than 5,000 species. They are mostly epiphytes, but include some terrestrials and myco-heterotrophs, all occurring in most tropical areas. The main stem grows in a single direction. Many of the species develop pseudobulbs (i.e. a bulge at the base of a stem), that are normally shorter and sturdier than those in the epidendroids. The striking characteristics of the vandoids are a cellular pollinium stalk (= stipe), superposed pollinia and the unique development of the incumbent anther, that bends early in development.
About 1,800 species in 100 to 130 genera. Species are either terrestrial or epiphytic, and range throughout global tropical regions. All species have, as a unique feature, a sympodial growth habit and two pollinia.
Subtribe Oncidiinae: Largest subtribe with nearly 1,000 species within about 56 to 78 genera, found in tropical America, the Caribbean and Florida. Most are epiphytes, but a few are terrestrials. They usually have short and stout pseudobulbs.
Alliance Oncidium: largest alliance; includes the majority of genera in cultivation.
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.
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.
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.
In the botanical classification of plants, Aeridinae is a subtribe of the tribe Vandeae whose representatives all have a monopodial growth habit and do not possess pseudobulbs.
Sobralia is a genus of orchids native to Mexico, Central and South America. The plants are more commonly terrestrial, but are also found growing epiphytically, in wet forests from sea level to about 8,800 ft. The genus was named for Dr. Francisco Sobral, a Spanish botanist. The genus is abbreviated Sob in trade journals.
The Orchidoideae, or the orchidoid orchids, are a subfamily of the orchid family (Orchidaceae).
Vanilloideae is one of the subfamilies of orchids belonging to the large family Orchidaceae.
Epidendrum, abbreviated Epi in the horticultural trade, is a large neotropical genus of the orchid family. With more than 1,500 species, some authors describe it as a mega-genus. The genus name refers to its epiphytic growth habit.
Laeliinae is a Neotropical subtribe including 40 orchid genera, such as Brassavola, Laelia and Cattleya. The genus Epidendrum is the largest within this subtribe, containing about 1500 species. This is followed by the genus Encyclia, with over 120 species.
Microchilus is a neotropical genus of about 75 species belonging to the orchid family (Orchidaceae).
The Vandeae is a large monophyletic tribe within the family of orchids.
Scaphyglottis is a genus of orchids native to Mexico, Central America, northern South America and parts of the Caribbean. The current concept of this genus is the result of combining several genera which have been described at various times. The concept is characterized by the growth habit: not only are new pseudobulbs added at the base of the old ones, but new pseudobulbs also grow at the apices of the old ones. Many species are quite similar and difficult to distinguish, but some are clearly distinct. A few have showy colors. The genus comprises nearly 70 species.
Elleanthus is a genus of flowering plants from the orchid family, Orchidaceae. They are commonly known as tiger orchid. All the species are native to the warmer parts of the Western Hemisphere.
Fernandezia is a genus of flowering plants from the orchid family, Orchidaceae. It contains about 30-40 species, native to northern South America, Central America, and southern Mexico.
Jacquiniella is a genus of flowering plants from the orchid family, Orchidaceae. It is native to Mexico, Central America, the West Indies, and South America.
Kefersteinia is a genus of flowering plants from the orchid family, Orchidaceae. It has about 40-50 species, widespread across much of Latin America. The genus was named for Keferstein of Kröllwitz, an orchidologist.
Oeceoclades, collectively known as the monk orchids, is a genus of flowering plants from the orchid family, Orchidaceae. It is related to Eulophia and like that genus is mostly terrestrial in habit. A few species extend into very arid environments, unusual for an orchid.
Angraecinae is a subtribe in the family Orchidaceae. The subtribe consists of approximately 18 genera and about 360 species. The type genus is Angraecum. Most of the genera are endemic to Africa, Madagascar and other Indian Ocean Islands, a few genera can also be found in the Americas.
The Eriinae form a subtribe of Podochileae, a tribe of the orchid family (Orchidaceae). The name is derived from the genus Eria.
Dendrobieae is a tribe in the subfamily Epidendroideae, in the family Orchidaceae. The Dendrobieae are mostly tropical, epiphytic orchids which contain pseudobulbs.
Maxillariinae is an orchid subtribe in the tribe Cymbidieae. It was formerly treated as the tribe Maxillarieae, and divided into a number of subtribes.
Podochileae is an orchid tribe in the subfamily Epidendroideae.
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↑ Robert L. Dressler. 1981. The Orchids: Natural History and Classification. Harvard University Press. ISBN978-0-674-87525-8. (See External links below).
↑ Robert L. Dressler. 1993. Phylogeny and Classification of the Orchid Family. Cambridge University Press. ISBN978-0-521-45058-4. 314 pages
↑ Kenneth M. Cameron, Mark W. Chase, W. Mark Whitten, Paul J. Kores, David C. Jarrell, Victor A. Albert, Tomohisa Yukawa, Harold G. Hills and Douglas H. Goldman. 1999. "A phylogenetic analysis of the Orchidaceae: evidence from rbcL nucleotide sequences". American Journal of Botany86 (2): 208-224. (See External links below).
↑ Mark W. Chase, Kenneth M. Cameron, Russell L. Barrett, and John V. Freudenstein. 2003. "DNA data and Orchidaceae systematics: a new phylogenetic classification". pages 69-89. In: Kingsley W. Dixon, Shelagh P. Kell, Russell L. Barrett, and Phillip J. Cribb (editors). 2003. Orchid Conservation. Natural History Publications, Kota Kinabalu, Sabah, Malaysia. ISBN978-983-812-078-4. (See External links below).
1 2 3 Mark W. Chase, Kenneth M. Cameron, John V. Freudenstein, Alec M. Pridgeon, Gerardo A. Salazar, Cássio van den Berg, and André Schuiteman. 2015. "An updated classification of Orchidaceae". Botanical Journal of the Linnean Society177 (2): 151-174. (See External links below).
↑ 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 (See External links below).
↑ Kenneth M. Cameron. 2006. "A comparison and combination of plastid atpB and rbcL gene sequences for inferring phylogenetic relationships within Orchidaceae". pages 447-464. In: J. Travis Columbus, Elizabeth A. Friar, J. Mark Porter, Linda M. Prince, and Michael G. Simpson (editors). Aliso22 (Monocots: Comparative Biology and Evolution). 735 pages. Rancho Santa Ana Botanic Garden. printed by Allen Press: USA.
↑ Kenneth M. Cameron. 2011. "Vanilloid Orchids: Systematics and Evolution". pages 1-14. In: Eric Odoux and Michel Grisoni (editors). Medicinal and Aromatic Plants – Industrial Profiles. CRC Press: Boca Raton FL, USA.