Acianthus

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Monocots
Ordo: Asparagales

Familia: Orchidaceae
Subfamilia: Orchidoideae
Tribus: Diurideae
Subtribus: Acianthinae
Genus: Acianthus
Overview of species (9)

A. amplexicaulis – A. caudatus – A. cuneatus – A. exsertus – A. fornicatus – A. ledwardii – A. saxatilis – A. scopulus – A. sinclairii
Name

Acianthus R.Br., Prodr. Fl. Nov. Holl.: 321 (1810)

Type species: Acianthus exsertus R.Br., Prodr. Fl. Nov. Holl.: 321 (1810)

Synonymy

Heterotypic
Spuricianthus Szlach. & Marg., Polish Bot. J. 46: 29 (2001)
Nemacianthus D.L.Jones & M.A.Clem., Orchadian 13: 440 (2002)
Acianthella D.L.Jones & M.A.Clem., Orchadian 14: 331 (2004)

Distribution
Native distribution areas:
Acianthus distribution

Australasia
Australia
New South Wales, Queensland, South Australia, Tasmania, Victoria.
New Zealand
Chatham Islands, Kermadec Islands, New Zealand North, New Zealand South.
Pacific
Southwestern Pacific
New Caledonia.

References: Brummitt, R.K. 2001. TDWG – World Geographical Scheme for Recording Plant Distributions, 2nd Edition
References
Primary references

Brown, R. 1810. Prodromus Florae Novae Hollandiae 321.
Pridgeon, A.M., Cribb, P.J., Chase, M.W. & Rasmussen, F.N. (eds.) 2001. Genera Orchidacearum Volume 2: Orchidoideae (Part one); page 66 ff., Oxford: Oxford University Press. ISBN 0-19-850710-0

Additional references

Kores, P.J. 1995: A systematic study of the genus Acianthus (Orchidaceae: Diurideae). Allertonia 7(3): 87–220. [Not seen, snippet view on Google books] Reference page.

Links

Global Biodiversity Information Facility. 2021. GBIF Backbone Taxonomy. Checklist dataset. Taxon: Acianthus. Accessed: 2021 Aug 5.
Govaerts, R. et al. 2021. Acianthus in Kew Science Plants of the World online. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the internet. Accessed: 2021 Aug 5. Reference page.
Govaerts, R. et al. 2021. Acianthus in World Checklist of Selected Plant Families. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the internet. Accessed: 2021 Aug 5. Reference page.
Hassler, M. 2021. Acianthus. World Plants: Synonymic Checklists of the Vascular Plants of the World In: Roskovh, Y., Abucay, L., Orrell, T., Nicolson, D., Bailly, N., Kirk, P., Bourgoin, T., DeWalt, R.E., Decock, W., De Wever, A., Nieukerken, E. van, Zarucchi, J. & Penev, L., eds. 2021. Species 2000 & ITIS Catalogue of Life. Published on the internet. Accessed: 2021 Aug 5. Reference page.
International Plant Names Index. 2021. Acianthus. Published online. Accessed: 5 Aug 2021.
Tropicos.org 2021. Acianthus. Missouri Botanical Garden. Published on the internet. Accessed: 2021 Aug 5.

Vernacular names

перем коми: Ациантус
коми: Ациантус
мокшень: Ациантус
олык марий: Ациантус
кырык мары: Ациантус
русский: Ацианта
удмурт: Ациантус

Acianthus, commonly known as mosquito orchids, is a genus of about twelve species of plants in the orchid family, Orchidaceae. Mosquito orchids are terrestrial herbs with a single, heart-shaped, usually ground-hugging leaf and one to many small, green, pinkish or purplish flowers on a fleshy stalk. They are found in New Caledonia, Australia and New Zealand.

Description

Orchids in the genus Acianthus are terrestrial, perennial, deciduous, sympodial herbs with a single egg-shaped, heart-shaped or lobed leaf at the base. They have small, roughly spherical, underground tubers from which the flower stems arise. Lacking true roots, they have root-like stolons which develop "daughter" tubers at their ends. These orchids spend the dry, summer months dormant until, following late-summer or autumn rains, the leaf appears. The leaf is glabrous, sometimes ground-hugging, more usually held above the ground and is often purplish-red on the lower surface. Sometimes the leaves of plants with flowers are different from those lacking them. The leaves of all Australian species are very similar, making them hard to identify to species level in the absence of flowers.[2][3][4][5][6][7][8][9]

Flowers appear in the cooler months, usually in autumn, winter or spring, There are one to many resupinate small, green, pinkish or purplish flowers 4 to 5 mm (0.16 to 0.20 in) in diameter. The flowers are held on an upright, narrow but fleshy stalk, blend in with their surrounding and often resemble mosquitoes. The sepals are longer than the petals and usually have a long, thin extension on their end. The dorsal sepal is broader than the lateral ones and sometimes forms a hood over the column. The lateral sepals project forward beneath the labellum and the petals spread widely or curve backwards against the ovary. The labellum is heart-shaped and has a prominent callus. The fruit is a thin-walled, glabrous capsule, containing a large number of winged seeds.[2][4][8][9]

Taxonomy and naming

The genus was first formally described by Robert Brown in 1810 in Prodromus Florae Novae Hollandiae. He described three species (A. fornicatus, A. exsertus and A. caudatus) but did not nominate a type species.[1][10] Orchids in this genus are closely related to those in the genus Caladenia.[3] Some Australian species, formerly included in Acianthus, have been transferred to other genera, such as Acianthella.

The genus name (Acianthus) is derived from the Greek ake or akis, "a point, needle" and anthos "flower" referring to the pointed perianth and the acuminate floral segments.[11][12]

Distribution and habitat

Of the 25 extant species, 15 are endemic to New Caledonia (including L'Île-des-Pins), 9 to Australia and one to New Zealand. (One species, A. ledwardii, described from Burleigh Heads in 1938, has not been seen since 1939. It is listed as "extinct" under the Australian Government Environment Protection and Biodiversity Conservation Act 1999.)[13] Of the Australian species, 7 are found in New South Wales, 6 in Queensland, 3 in Victoria and 2 in South Australia. The sole New Zealand example, A. sinclairii occurs on both North and South Islands, as well as on Raoul, Stewart, Chatham and Three Kings Islands.[6][14]

Mosquito orchids species grow in small groups in forests on decaying litter, occasionally on partially decayed logs. They sometimes form dense vegetative colonies, in sheltered forest or heathland, and are often found underneath shrubs and bracken.[3]

Ecology

The labellum of Acianthus species produces a sweet nectar which is contained in a sunken area at the base of the labellum. The flowers of Australian species open in sequence up the flowering spike, each flower open for a few days, and are pollinated by fungus gnats from the families Anisopodidae, Sciaridae and Mycetophilidae. Usually only a small percentage of the plants in a colony have flowers. Flies on Acianthus caudatus have been observed to move up the labellum, probing with their proboscis until they reach the nectar, where the up and down "pumping" action of their bodies brings them into contact with the viscidium and pollinia which then adhere to the insect's body. When these are carried to another flower, a similar action causes the pollinia to attach to the receptive stigma.[2][4][6][9]

Use in horticulture

Mosquito orchids are easy to grow in plastic or ceramic pots. They need to be watered regularly except when dormant over summer and to be repotted every one or two years.[6][15]
Species

The following is a list of Acianthus species accepted by Plants of the World Online as at February 2021:[16]

Acianthus amplexicaulis (F.M.Bailey) Rolfe – green elf orchid (New South Wales, Queensland, New Caledonia)
Acianthus borealis D.L.Jones – northern mosquito orchid (Queensland)
Acianthus caudatus R.Br. – mayfly orchid (Queensland, New South Wales, Victoria, South Australia and Tasmania)
Acianthus collinus D.L.Jones – hooded mosquito orchid (New South Wales and the Australian Capital Territory)
Acianthus cuneatus D.L.Jones & L.M.Copel. (New South Wales)
Acianthus exiguus D.L.Jones – tiny mosquito orchid (New South Wales)
Acianthus exsertus R.Br. – gnat orchid, large mosquito orchid (Queensland, New South Wales, ACT, Victoria )
Acianthus fornicatus R.Br. – pixie-caps (Queensland, New South Wales)
Acianthus ledwardii Rupp – Ledward's mosquito orchid (Queensland)
Acianthus pusillus D.L.Jones – small mosquito orchid (Queensland, New South Wales, Victoria, South Australia, Tasmania)
Acianthus saxatilis D.L.Jones & M.A.Clem. (Queensland)
Acianthus sinclairii Hook.f. – heart-leaved orchid, pixie cap (New Zealand)

Former species

Acianthus apprimus D.L.Jones, A. borealis D.L.Jones, A. collinus D.L.Jones and A. exiguus D.L.Jones are now considered to be synonyms of A. fornicatus and A. pusillus to be a synonym of A. exsertus.[16]

The following species were formerly placed in Acianthus but have since been transferred to other genera:

Acianthus huegelii - now classified as a variety, Cyrtostylis reniformis var. huegelii.
Acianthus reniformis - (Western Australia) now classified as Cyrtostylis reniformis.
Acianthus sublestus (NE Queensland) - now classified as Acianthella sublesta
Acianthus tenuissimus - (Western Australia) now classified as Cyrtostylis tenuissima.

References

"Acianthus". APNI. Retrieved 16 September 2019.
Jones, David L. (2006). A complete guide to native orchids of Australia including the island territories. Frenchs Forest, N.S.W.: New Holland. p. 161. ISBN 1-877069-12-4.
Hoffman, Noel; Brown, Andrew (1984). Orchids of south-west Australia (2 ed.). Nedlands, W.A.: University of Western Australia Press. p. 189. ISBN 0855642262.
Bishop, Anthony (1996). Field guide to the orchids of New South Wales and Victoria. Sydney: UNSW Press. p. 172. ISBN 086840375X.
Backhouse, Gary; Jeanes, Jeffrey (1995). The orchids of Victoria (1st ed.). Carlton, Vic.: Miegunyah Press. ISBN 052284393X.
Pridgeon (ed.), Alec M.; Cribb (ed.), Phillip J.; Chase (ed.), Mark W.; Rasmussen (ed.), Finn (2001). Genera Orchidacearum (Volume 2), Orchidoideae (part 1). Oxford, England: Oxford University Press. pp. 68–70. ISBN 0198507100.
"Acianthus". Royal Botanic Gardens Sydney: plantnet. Retrieved 9 June 2016.
"Acianthus". Government of South Australia: efloraSA. Retrieved 9 June 2016.
"Acianthus". Australian National Botanic Gardens. Retrieved 12 June 2016.
Brown, Robert (1810). Prodromus Florae Novae Hollandiae. London. pp. 321–322. Retrieved 9 June 2016.
Quattrocchi, Umberto (2000). CRC world dictionary of plant names : common names, scientific names, eponyms, synonyms, and etymology (Volume 1). CRC Press. p. 30. ISBN 0849326737.
"Acianthus sinclairii" New Zealand Plant Conservation Network. Retrieved 15 July 2019.
"SPRAT Profile Acianthus ledwardii". Australian Government Dapartment of Agriculture, Water and the Environment. Retrieved 24 February 2021.
"Acianthus sinclairii" New Zealand Plant Conservation Network. Retrieved 9 June 2016.
Jones, David L. (2006). A complete guide to native orchids of Australia including the island territories. Frenchs Forest, N.S.W.: New Holland. p. 301. ISBN 1-877069-12-4.
"Acianthus". Plants of the World Online. Retrieved 24 February 2021.