Cycas is the type genus and the only genus recognised in the familyCycadaceae. About 113 species are accepted.Cycas circinalis, a species endemic to India was the first cycad species to be described and was the type of the generic name, Cycas. The best-known Cycas species is Cycas revoluta. Cycas is a very ancient genus of trees. The group achieved its maximum diversity in the Jurassic and Cretaceous periods, when it was distributed almost worldwide. At the end of the Cretaceous, when the non-avian dinosaurs became extinct, so did most of the cycas in the Northern Hemisphere.
See also: List of cycad species by country
The genus is native to the Old World, with the species concentrated around the equatorial regions - eastern and southeastern Asia including the Philippines with 10 species (9 of which are endemic), eastern Africa (including Madagascar), northern Australia, Polynesia, and Micronesia. Australia has 26 species, while the Indo-Chinese area has about 30. India has 9 species. The northernmost species (C. revoluta) is found at 31°N in southern Japan. The southernmost (C. megacarpa) is found at 26°S in southeast Queensland. Due to the occurrence of large number of Cycas species in China and Australia, both the countries are considered as two centres of diversity of Cycas.
Often considered a living fossil, the earliest fossils of the genus Cycas appear in the Cenozoic although Cycas-like fossils that may belong to Cycadaceae extend well into the Mesozoic. Cycas is not closely related to other genera of cycads, and phylogenetic studies have shown that Cycadaceae is the sister-group to all other extant cycads.
The plants are dioecious, and the family Cycadaceae is unique among the cycads in not forming seed cones on female plants, but rather a group of leaf-like structures called megasporophylls each with seeds on the lower margins, and pollen cones or strobilus on male individuals.
The caudex is cylindrical, surrounded by the persistent petiole bases. Most species form distinct branched or unbranched trunks but in some species the main trunk can be subterranean with the leaf crown appearing to arise directly from the ground. There are two types of leaves - foliage leaves and scaly leaves. The foliage leaves are pinnate (or more rarely bipinnate) and arranged spirally, with thick and hard keratinose. They are not permanent and fall off leaving back leaf-bases. The leaflets are articulated, have midrib but lack secondary veins. The scaly leaves are persistent, brown in colour and protective in function. Megasporophylls are not gathered in cones. Pollination takes place by air.
The plant takes several years to grow, sexual reproduction takes place after 10 years of exclusive vegetative growth which occurs by bulbils arising at the base of the trunk.
Cycas species are threatened worldwide and almost all the species are listed in IUCN Redlist. Cycas beddomei is the only species of the genus Cycas listed in Appendix I of CITES. Cycas rumphii and Cycas pectinata have the most widespread distribution.
List of species
References and external links
|Wikimedia Commons has media related to Cycas.|
- de Laubenfels, David J.; Adema, F. (1998). "A taxonomic revision of the genera Cycas and Epicycas Gen. Nov. (Cycadaceae)". Blumea. 43: 351–400.
- Hill, K.D.(1998–2004) The Cycad Pages, Royal Botanic Gardens Sydney. http://plantnet.rbgsyd.nsw.gov.au/PlantNet/cycad/index.html
- Virtual Cycad Encyclopedia edited by the Palm & Cycad Societies of Florida
- David, J. de Laubenfels, Cycas Taxonomy
- Hill, K.D.; Stevenson, Dennis W.; Osborne, Roy (2004). "The World List of Cycads". The Botanical Review. 70 (2): 274–298. doi:10.1663/0006-8101(2004)070[0274:TWLOC]2.0.CO;2.
- Lindstrom, Anders J.; Hill, Ken D. (2007). "The genus Cycas (Cycadaceae) in India". Telopea. 11 (4): 463–488. doi:10.7751/telopea20075745.
- Singh, R & JS Khuraijam (2013-) Cycads of India. http://www.cycadsofindia.in/
- Singh, R.; Radha, P.; Khuraijam, J.S. (2015). "A new species, a new combination and a new subsection of Cycas from Odisha, northern Eastern Ghats of India". Asian Journal of Conservation Biology. 4 (1): 3–14.
- Singh, R.; Radha, P. (2006). "Cycas annaikalensis, A new species of Cycas from the Malabar Coast, Western Ghats, India". Brittonia. 58 (2): 119–123. doi:10.1663/0007-196x(2006)58[119:ansocf]2.0.co;2.
- Terrence Walters & Roy Osborne (eds.) (2004), Cycad Classification: Concepts and Recommendations, CABI publishing, ISBN 0-85199-741-4
|Scientific Name:||Cycas rumphii Miq.|
Cycas celebica Miq.
Assessment Information [top]
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Reviewer(s):||Donaldson, J.S. & Bösenberg, J.D.|
Occurs over a wide range in coastal areas, but this species has declined due to habitat loss (20% in the last 50 years) and may qualify under criterion A if habitat loss increases. It s therefore listed as Near Threatened as it almost qualifies for a threatened listing under criterion A2c.
|Previously published Red List assessments:|
Geographic Range [top]
|Range Description:||C. rumphii has a distribution centred on the Moluccan island group (Maluku, or the Spice Islands) extending east into Indonesian Papua and a short way along the north coast of Papua New Guinea, and north to Sulawesi. In the west, it appears to extend to southern Borneo and northeastern Java. Occurs from 10 to 200 m.|
Native:Indonesia (Jawa, Maluku, Papua, Sulawesi); Papua New Guinea (Papua New Guinea (main island group))
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The species is locally abundant.|
|Current Population Trend:||Decreasing|
Habitat and Ecology [top]
|Habitat and Ecology:||This species grows in coastal and near coastal communities in littoral forest and rainforest. Often on stabilized dunes composed of coral sands and coral limestone.|
|Generation Length (years):||40|
|Major Threat(s):||The threats to this species are unknown although there has been loss of habitat across its range.|
Conservation Actions [top]
|Conservation Actions:||This species is listed on Appendix II of the CITES Appendices.|