Disa (plant)

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Disa
Disa cardinalis 250603.jpg
Disa cardinalis
Disa tenuis 197444465.jpg
Disa tenuis
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Orchidaceae
Subfamily: Orchidoideae
Tribe: Orchideae
Subtribe: Disinae
Genus: Disa
P.J.Bergius 1767
Type species
Disa uniflora
Species

See text

Synonyms
List
  • RepandraLindl.
  • PentheaLindl.
  • ForficariaLindl.
  • GamariaRaf.
  • HerscheliaLindl.
  • MonadeniaLindl.
  • SchizodiumLindl.
  • OrthopentheaRolfe in W.H.Harvey
  • AmphigenaRolfe in W.H.Harvey
  • HerscheliantheRauschert
  • × HerscheliodisaH.P.Linder

Disa is a genus of flowering plants in the family Orchidaceae. It comprises about 182 species. [1] [2] Most of the species are indigenous to tropical and southern Africa, with a few more in the Arabian Peninsula, Madagascar, and Réunion. [3] Disa bracteata is naturalised in Western Australia, where the local name is "African weed-orchid." [4]

Contents

The genus Disa was named by P.J. Bergius in 1767. [5] [6] It was named after Disa, the heroine of a Swedish legend. [7]

Description

The plants grow from a fleshy tuberous root which is a source of maltodextrins which are used as a sugar substitute. Some species attain a height of 90 cm. The flowers are solitary or arranged in racemes. The petals and the lip are small. The flowers consist essentially of the sepals. The flowers range in color from very light to dark red.

Pollination

Disa exhibits a variety of pollination syndromes. Each species of Disa usually has a single species as pollinator and nearly every available pollinating insect is employed by some species of Disa. Species that adapted to the same pollinator often independently evolved a similar floral morphology which confounded the infrageneric classification of Disa until cladistic analysis was applied to DNA sequences from this genus. [8]

Examples of convergent evolution in Disa pollination include the following:

Disa serves as an example of how speciation can be caused by changes in pollinator availability and evolution.

Some Disa species are pollinated by sunbirds and have pollinaria that stick to the feet of the sunbirds when they perch on the inflorescence. [11]

Phylogeny

The first molecular phylogeny of the genus involved comparison of nuclear ribosomal ITS1, 5.8S rDNA, and ITS2 sequences, and showed that Herschelia and Monadenia were nested within a paraphyletic Disa. [12]

In Genera Orchidacearum volume 2, Disa and Schizodium compose the subtribe Disinae of the tribe Diseae. [13] After that volume was published in 2001, molecular phylogenetic studies showed that Schizodium is nested within Disa. [14] [15] Schizodium comprises only six species, all endemic to South Africa. [16]

In a classification of orchids that was published in 2015, Chase et alii placed Schizodium in synonymy under Disa. They also defined the subtribe Disinae as consisting of Pachites , Disa and Huttonaea . This version of Disinae is probably not monophyletic, but was created as a holding classification, to avoid the unnecessary designation of subtribes before further studies can clarify the relationships of these three genera. [1]

Seeds

The genus can be split into two groups based on the size of the seeds. Those with relatively large balloon-shaped seeds up to 1.5 mm long belong to the Disa uniflora group. The remaining species have seeds that are smaller than 0.7 mm. The Disa uniflora group comprises plants that grow along stream sides: Disa uniflora , Disa tripetaloides , Disa cardinalis , Disa caulescens and Disa aurata . They belong to the few species in Orchidaceae that do not rely on mycorrhizal fungi for germination, and are thought to be an adaptation to hydrochory. [17] [18] This pattern was later extended to split the genus into summer rainfall species and non-summer rainfall species. Those in the second group added Disa cornuta to the list of Disa seeds that germinate readily. [19]

Horticulture

The species Disa uniflora is well known as an ornamental. It is a spectacular red orchid known as "The Pride of Table Mountain." [20] Other commonly cultivated species include Disa aurata, Disa cardinalis, Disa crassicornis, Disa racemosa, Disa sagittalis , and Disa tripetaloides . [21] Some of the species are grown only in African gardens. [22]

Once very rare in cultivation, Disa uniflora is gaining in popularity as a cut flower. However, they are difficult to grow, because of the needed mineral composition of the potting soil. Also, if exposed to excessive moisture, they can be easily killed by rot.

Hybrids

Disa uniflora flowers. RedDisa.jpg
Disa uniflora flowers.

The following species have been used to create more than 400 hybrids : Disa cardinalis, Disa caulescens, Disa racemosa, Disa tripetaloides, Disa uniflora, Disa aurata and Disa venosa.

Species

Disa atricapilla Disa atricapilla 338555196.jpg
Disa atricapilla
Disa atrorubens Disa atrorubens 435082705.jpg
Disa atrorubens
Disa aurata Disa aurata 2084.jpg
Disa aurata
Disa baurii Disa baurii 436641926.jpg
Disa baurii
Disa bivalvata Disa bivalvata 340179494.jpg
Disa bivalvata
Disa caffra Disa caffra 109483465 (cropped).jpg
Disa caffra
Disa chrysostachya Disa chrysostachya 2016 01 02 4349.jpg
Disa chrysostachya
Disa comosa Disa comosa (2).jpg
Disa comosa
Disa ferruginea Disa ferruginea 354748896.jpg
Disa ferruginea
Disa graminifolia Disa Graminifolia.jpg
Disa graminifolia
Disa longicornu Disa longicornu02.jpg
Disa longicornu
Disa polygonoides Disa polygonoides 251920844 (cropped).jpg
Disa polygonoides
Disa purpurascens Disa purpuracens.jpeg
Disa purpurascens

Species currently (May 2014) recognized: [2]

Related Research Articles

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<i>Hyparrhenia</i> Genus of grasses

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<i>Disa uniflora</i> Species of flowering plants in the orchid family

Disa uniflora, the red disa or pride of Table Mountain, is a South African species of orchid in the family Orchidaceae. It is the type species of the genus Disa, and one of its best-known members. It is occasionally referred to by its old name Disa grandiflora.

<i>Disa bracteata</i> South African plant species in the orchid family

Disa bracteata, also known as the bract disa, leek orchid or the South African weed orchid is a species of orchid native to South Africa.

<i>Disa purpurascens</i> Species of orchid

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<i>Disa sagittalis</i> Species of orchid

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<i>Bolusiella</i> Genus of orchids

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<i>Pterygodium</i> Genus of flowering plants belonging to the orchid family

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<i>Disa ferruginea</i> Species of flowering plant

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<i>Microcoelia exilis</i> Species of orchid

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References

  1. 1 2 Mark W. Chase; Kenneth M. Cameron; John V. Freudenstein; Alec M. Pridgeon; Gerardo A. Salazar; Cássio van den Berg; André Schuiteman (2015). "An updated classification of Orchidaceae". Botanical Journal of the Linnean Society. 177 (2): 151–174. doi: 10.1111/boj.12234 .
  2. 1 2 Kew World Checklist of Selected Plant Families
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  4. Weeds Australia, Weed Identification, African weed-orchid, Disa bracteata Archived May 17, 2014, at the Wayback Machine
  5. "Disa Query Results". International Plant Names Index .
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  8. Waterman, Richard J.; Pauw, Anton; Barraclough, Timothy G.; Savolainen, Vincent (2009). "Pollinators underestimated: A molecular phylogeny reveals widespread floral convergence in oil-secreting orchids (sub-tribe Coryciinae) of the Cape of South Africa". Molecular Phylogenetics and Evolution. 51 (1): 100–110. doi:10.1016/j.ympev.2008.05.020. PMID   18586527.
  9. Johnson, S.D.; Linder, H.P.; Steiner, K.E. (1998). "Phylogeny and radiation of pollination systems in Disa (Orchidaceae)". American Journal of Botany. 85 (3): 402–411. doi: 10.2307/2446333 . JSTOR   2446333.
  10. Johnson, S (September 1994). "Evidence for Batesian mimicry in a butterfly-pollinated orchid". Biological Journal of the Linnean Society. 53 (1): 91–104. doi:10.1006/bijl.1994.1062.
  11. Johnson, S. D.; Brown, M. (2004). "Transfer of pollinaria on birds' feet: a new pollination system in orchids". Plant Systematics and Evolution. 244 (3): 181–188. doi:10.1007/s00606-003-0106-y. S2CID   23288375.
  12. Douzery, Emmanuel J. P.; Pridgeon, Alec M.; Kores, Paul; Linder, H. P.; Kurzweil, Hubert; Chase, Mark W. (1999-06-01). "Molecular phylogenetics of Diseae (Orchidaceae): a contribution from nuclear ribosomal ITS sequences". American Journal of Botany. 86 (6): 887–899. doi:10.2307/2656709. ISSN   0002-9122. JSTOR   2656709. PMID   10371730.
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  14. Bytebier, Benny; Bellstedt, Dirk U.; Linder, Hans Peter (2007). "A molecular phylogeny for the large African orchid genus Disa". Molecular Phylogenetics and Evolution. 43 (1): 75–90. doi:10.1016/j.ympev.2006.08.014. PMID   17081772.
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  16. Linder Hans Peter (1981). "Taxonomic studies on the Disinae: 2. A revision of the genus Schizodium Lindl". Journal of South African Botany. 47: 339–371.
  17. Thompson, David Ian (2003). Conservation of select South African Disa Berg. Species (Orchidaceae) through in vitro seed germination. University of Natal.
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  19. Thompson, Dave I.; Edwards, Trevor J.; Staden, Johannes van (2001). "In Vitro Germination of Several South African Summer Rainfall Disa (Orchidaceae) Species: Is Seed Testa Structure a Function of Habitat and a Determinant of Germinability?". Systematics and Geography of Plants. 71 (2): 597–606. doi:10.2307/3668704. JSTOR   3668704.
  20. PlantZAfrica.com, Disa uniflora Bergius
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