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Taxonomy of the Orchid family



         


The following taxonomy of the orchid family (Orchidaceae) follows the classification system of Robert Louis Dressler, an orchid specialist and adjunct curator at the Florida Museum of Natural History. This classification, published in the book "The Orchids: Natural History and Classification", is widely accepted by botanists and growers. The initial scheme of 1981 has been modified in 1986, twice in 1990. and again in 1993. This is the most comprehensive classification at the moment. But it relies heavily on morphology and a few key characters. According to morphological cladistics, the Orchid family is a monophyletic group. There is a great similarity with the traditional taxonomy, but on lower levels, matters are still unresolved. Cladistic methods give us a firmer basis, but the classification is still an ongoing issue. Furthermore, about 150 new species and even new genera are still being discovered each year.


The orchid family is subdivided in several several subfamilies, and then in tribes, subtribes, alliances and then genera. The following six subfamilies are recognized :


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Subfamily SPIRANTHOIDEAE

This subfamily contains some 550 species in about 95 genera..The species can be identified by the basic column structure. They also lack root-stem tuberoids. Tribe ERYTHRODEAE

All species in this tribe occur in Asia, Africa, and Australia.

Tribe CRANICHIDEAE

Species of this tribe occur in North and South America.


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Subfamily ORCHIDOIDEAE

This subfamily contains some 2,800 species. occurring in the temperate climates of Europe, Africa, and Australia. The species are mainly terrestrial plants with slender stems, spiraling leaves, and mealy pollen. They all have a unique thickened root-stem tuberoid storage organ.

Tribe DIURIDEAE  : about 550 species

Tribe ORCHIDEAE : largest tribe, containing more than 1,700 species.

Tribe DISEAE


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Subfamily EPIDENDROIDEAE

This is the largest subfamily. It comprises more than 10,000 species in about 90 to 100 genera. Most are tropical epiphytes (usually with pseudobulbs), but some are terrestrials and even a few saprophytes. All show a unique development of the anther. Most have hard pollinia, i.e. a mass of waxy pollen or of coherent pollen grains.

Tribe NEOTTIEAE : about 100 species.

Tribe VANILLEAE : over 200 species.

Tribe GASTRODIEAE

Tribe EPIPOGIEAE

Tribe ARETHUSEAE : over 500 species.

Tribe COELOGTNEAE : over 400 species.

Tribe MALAXIDEAE : over 900 species.

Tribe CRYPTARRHENEAE

Tribe CALYPSOEAE

Tribe EPIDENDREAE : cosmopolitan and also largest tribe of this subfamily,with over 8,000 species.

Tribe TROPIDIINAE (was formerly placed in the subfamily Spiranthoideae)


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Subfamily VANDOIDEAE

This is the second largest subfamily with over 300 genera and more than 5,000 species. They are mostly epiphytic, but include some terrestrials and saprophytes.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 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.

Tribe POLYSTACHYEAE : about 200 species, which all show four pollinia. The lip often has mealy hairs, called pseudopollen, on the upper surface.

Tribe VANDEAE : over 1,700 species in more than 130 genera; occurs in tropical Asia, Pacific islands, Australia, and Africa.

Tribe MAXILLARIEAE : 70 to 80 genera with about 1,000 species; Most grow in tropical American as terrestrials or epiphytes, a few are saprophytes. Most show pseudobulbs, but a few have reedlike stems or thick underground stems. Blooms have four pollinia.

Tribe CYMBIDIEAE : 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 unique feature, a sympodial growth habit and two pollinia.


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Subfamily APOSTASIOIDEAE

Two genera with about 16 species. These rare orchids have two or three lateral anthers. Several primitive features makes them, according to some authorities, not true orchids but rather ancestors of modern orchids.


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Subfamily CYPRIPEDIOIDEAE

Four or five genera with about 115 species; mostly terrestrials or lithophytes. They lack pseudobulbs and show a unique shieldlike staminode, i.e. a sterile stamen, and pouchlike lip.


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Not assigned

These two tribes are not currently assigned to a specific subfamily Tribe TRIPHOREAE : A primitive tribe consisting of three genera and twenty species. Possibly belongs to the Epidendrum subfamily.

Tribe WULLSCHLAEGELIEAE : one genus with two species.


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Reference


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