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Cycas

January 24, 2023

Cycas is a genus of plants belonging to a very ancient lineage, the Cycadophyta, which are not closely related to palms, ferns, trees or any other modern group of plants. They are evergreen perennials which achieved their maximum diversity in the Jurassic and Cretaceous periods, when they were 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.

Cycas
Temporal range: Paleogene–Recent
A large cycas under development
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnosperms
Division: Cycadophyta
Class: Cycadopsida
Order: Cycadales
Suborder: Cycadineae
Family: Cycadaceae
Pers.[2]
Genus: Cycas
L.[1]
Type species
C. circinalis[1]
L.[1]
Synonyms[3]
  • Todda-pana Adans.
  • Dyerocycas Nakai
  • Epicycas de Laub.
  • Eucycas

Cycas is the type genus and the only extant genus recognised in the family Cycadaceae. About 113 species are accepted.[4] Cycas circinalis, a species endemic to India, was the first cycad species to be described in western literature, and was the type of the generic name, Cycas. The best-known Cycas species is Cycas revoluta.

Range

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, Australia and India, those countries are considered as centres of Cycas diversity.[3]

Evolution

 
Cycas sp.

Cycas is though to have split from all other living cycads at least 200 million years ago, possibly much earlier. Fossil seeds from the Middle Jurassic of England and British Columbia, were suggested in a 2017 study to be more closely related to Cycas than other cycads, were assigned to the same family, Cycadaceae.[5] However, a later study suggested that these seeds could not be assigned to the stem-group of Cycas with confidence due to lacking the double vascular system that characterises the seeds of all living cycads.[6] The earliest fossils assignable to Cycas are known from the Paleogene of East Asia, such as Cycas fushunensis from the Eocene of Northeast China, with East Asia likely representing the ancestral homeland of the genus.[7]

Morphology

 
Bark of Cycas rumphii

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.

Reproduction

 
A male cone of Cycas circinalis
 
A male cone of Cycas orixensis with unique forked microsporophylls

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.

Conservation status

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

 
Cycas media megasporophylls with nearly-mature seeds on a wild plant in north Queensland, Australia
 
Grove of Cycas media in north Queensland
 
Cycas platyphylla in north Queensland with new flush of fronds during the rainy season, still with glaucous bloom

References

  1. ^ a b c Hill, Ken; Leonie Stanberg; Dennis Stevenson. . Genus Cycas. Royal Botanic Gardens Sydney. Archived from the original on 2021-03-01. Retrieved 6 September 2013.
  2. ^ Kramer, K.U.; Green, P.S., eds. (1990). Pteridophytes and Gymnosperms (PDF). The families and genera of vascular plants. Vol. 1. Assisted by E. Götz (illustrations). Berlin: Springer-Verlag. p. 370. ISBN 978-3-540-51794-8.
  3. ^ a b Kew World Checklist of Selected Plant Families
  4. ^ The World List of Cycads
  5. ^ Spencer, Alan R. T.; Garwood, Russell J.; Rees, Andrew R.; Raine, Robert J.; Rothwell, Gar W.; Hollingworth, Neville T. J.; Hilton, Jason (2017-08-28). "New insights into Mesozoic cycad evolution: an exploration of anatomically preserved Cycadaceae seeds from the Jurassic Oxford Clay biota". PeerJ. 5: e3723. doi:10.7717/peerj.3723. ISSN 2167-8359. PMC 5578371. PMID 28875075.
  6. ^ Rothwell, Gar W.; Stockey, Ruth A.; Stevenson, Dennis W.; Zumajo-Cardona, Cecilia (2022-10-01). "Large Permineralized Seeds in the Jurassic of Haida Gwaii, Western Canada: Exploring the Mode and Tempo of Cycad Evolution". International Journal of Plant Sciences. 183 (8): 674–690. doi:10.1086/721710. ISSN 1058-5893. S2CID 251947260.
  7. ^ Liu, Jian; Lindstrom, Anders J; Marler, Thomas E; Gong, Xun (2022-01-28). "Not that young: combining plastid phylogenomic, plate tectonic and fossil evidence indicates a Palaeogene diversification of Cycadaceae". Annals of Botany. 129 (2): 217–230. doi:10.1093/aob/mcab118. ISSN 0305-7364. PMC 8796677. PMID 34520529.

External links

 
Wikimedia Commons has media related to Cycas.
 
Wikispecies has information related to Cycas.
  • de Laubenfels, D.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 2021-03-29 at the Wayback Machine
  • edited by the Palm & Cycad Societies of Florida
  • David, J. de Laubenfels,
  • 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. S2CID 36921733.
  • 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. S2CID 32241023.
  • Terrence Walters & Roy Osborne (eds.) (2004), Cycad Classification: Concepts and Recommendations, CABI publishing, ISBN 0-85199-741-4

January 24, 2023
cycas, genus, plants, belonging, very, ancient, lineage, cycadophyta, which, closely, related, palms, ferns, trees, other, modern, group, plants, they, evergreen, perennials, which, achieved, their, maximum, diversity, jurassic, cretaceous, periods, when, they. Cycas is a genus of plants belonging to a very ancient lineage the Cycadophyta which are not closely related to palms ferns trees or any other modern group of plants They are evergreen perennials which achieved their maximum diversity in the Jurassic and Cretaceous periods when they were 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 CycasTemporal range Paleogene Recent PreꞒ Ꞓ O S D C P T J K Pg NA large cycas under developmentScientific classificationKingdom PlantaeClade TracheophytesClade GymnospermsDivision CycadophytaClass CycadopsidaOrder CycadalesSuborder CycadineaeFamily CycadaceaePers 2 Genus CycasL 1 Type speciesC circinalis 1 L 1 Synonyms 3 Todda pana Adans Dyerocycas Nakai Epicycas de Laub EucycasCycas is the type genus and the only extant genus recognised in the family Cycadaceae About 113 species are accepted 4 Cycas circinalis a species endemic to India was the first cycad species to be described in western literature and was the type of the generic name Cycas The best known Cycas species is Cycas revoluta Contents 1 Range 2 Evolution 3 Morphology 4 Reproduction 5 Conservation status 6 List of species 7 References 8 External linksRange EditSee 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 Australia and India those countries are considered as centres of Cycas diversity 3 Evolution Edit Cycas sp Cycas is though to have split from all other living cycads at least 200 million years ago possibly much earlier Fossil seeds from the Middle Jurassic of England and British Columbia were suggested in a 2017 study to be more closely related to Cycas than other cycads were assigned to the same family Cycadaceae 5 However a later study suggested that these seeds could not be assigned to the stem group of Cycas with confidence due to lacking the double vascular system that characterises the seeds of all living cycads 6 The earliest fossils assignable to Cycas are known from the Paleogene of East Asia such as Cycas fushunensis from the Eocene of Northeast China with East Asia likely representing the ancestral homeland of the genus 7 Morphology Edit Bark of Cycas rumphii 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 Reproduction Edit A male cone of Cycas circinalis A male cone of Cycas orixensis with unique forked microsporophylls 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 Conservation status EditCycas 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 distributionList of species Edit Cycas media megasporophylls with nearly mature seeds on a wild plant in north Queensland Australia Grove of Cycas media in north Queensland Cycas platyphylla in north Queensland with new flush of fronds during the rainy season still with glaucous bloom Cycas aculeata Cycas aenigma Cycas angulata Cycas annaikalensis Cycas apoa Cycas arenicola Cycas armstrongii Cycas arnhemica Cycas badensis Cycas balansae Cycas basaltica Cycas beddomei Cycas bifida Cycas bougainvilleana Cycas brachycantha Cycas brunnea Cycas cairnsiana Cycas calcicola Cycas campestris Cycas canalis Cycas candida Cycas cantafolia Cycas chamaoensis Cycas changjiangensis Cycas chenii Cycas chevalieri Cycas circinalis Cycas clivicola Cycas collina Cycas condaoensis Cycas conferta Cycas couttsiana Cycas cupida Cycas curranii Cycas debaoensis Cycas desolata Cycas diannanensis Cycas distans P I Forst amp B Gray Cycas dolichophylla Cycas edentata Cycas elephantipes Cycas elongata Cycas falcata Cycas fairylakea Cycas ferruginea Cycas fugax Cycas furfuracea Cycas glauca Cycas guizhouensis Cycas hainanensis Cycas hoabinhensis Cycas hongheensis Cycas indica Cycas swamyi Cycas inermis Cycas javana Cycas lacrimans Cycas lane poolei Cycas lindstromii Cycas litoralis Cycas maconochiei Cycas macrocarpa Cycas media Cycas megacarpa Cycas micholitzii Cycas micronesica Cycas montana Cycas multipinnata Cycas nathorstii Cycas nayagarhensis Cycas nitida Cycas nongnoochiae Cycas ophiolitica Cycas orientis Cycas orixensis Cycas pachypoda Cycas panzhihuaensis Cycas papuana Cycas pectinata Cycas petraea Cycas platyphylla Cycas pranburiensis Cycas pruinosa Cycas revoluta Sago palm Cycas riuminiana Cycas rumphii Miq Cycas sancti lasallei Cycas sainathii Cycas saxatilis Cycas schumanniana Cycas scratchleyana Cycas seemannii A Braun Cycas segmentifida Cycas semota Cycas sexseminifera Cycas shanyaensis Cycas siamensis Cycas silvestris Cycas simplicipinna Cycas sphaerica Cycas sundaica Cycas szechuanensis Cycas taitungensis Cycas taiwaniana Cycas tanqingii Cycas tansachana Cycas thouarsii Cycas tropophylla Cycas tuckeri Cycas vespertilio Cycas wadei Cycas xipholepis Cycas yorkiana Cycas yunnanensis Cycas zambalensis Cycas zeylanicaReferences Edit a b c Hill Ken Leonie Stanberg Dennis Stevenson The Cycad Pages Genus Cycas Royal Botanic Gardens Sydney Archived from the original on 2021 03 01 Retrieved 6 September 2013 Kramer K U Green P S eds 1990 Pteridophytes and Gymnosperms PDF The families and genera of vascular plants Vol 1 Assisted by E Gotz illustrations Berlin Springer Verlag p 370 ISBN 978 3 540 51794 8 a b Kew World Checklist of Selected Plant Families The World List of Cycads Spencer Alan R T Garwood Russell J Rees Andrew R Raine Robert J Rothwell Gar W Hollingworth Neville T J Hilton Jason 2017 08 28 New insights into Mesozoic cycad evolution an exploration of anatomically preserved Cycadaceae seeds from the Jurassic Oxford Clay biota PeerJ 5 e3723 doi 10 7717 peerj 3723 ISSN 2167 8359 PMC 5578371 PMID 28875075 Rothwell Gar W Stockey Ruth A Stevenson Dennis W Zumajo Cardona Cecilia 2022 10 01 Large Permineralized Seeds in the Jurassic of Haida Gwaii Western Canada Exploring the Mode and Tempo of Cycad Evolution International Journal of Plant Sciences 183 8 674 690 doi 10 1086 721710 ISSN 1058 5893 S2CID 251947260 Liu Jian Lindstrom Anders J Marler Thomas E Gong Xun 2022 01 28 Not that young combining plastid phylogenomic plate tectonic and fossil evidence indicates a Palaeogene diversification of Cycadaceae Annals of Botany 129 2 217 230 doi 10 1093 aob mcab118 ISSN 0305 7364 PMC 8796677 PMID 34520529 External links Edit Wikimedia Commons has media related to Cycas Wikispecies has information related to Cycas de Laubenfels D 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 Archived 2021 03 29 at the Wayback Machine Virtual Cycad Encyclopedia edited by the Palm amp 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 S2CID 36921733 Lindstrom Anders J Hill Ken D 2007 The genus Cycas Cycadaceae in India Telopea 11 4 463 488 doi 10 7751 telopea20075745 Singh R amp 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 ofCycasfrom the Malabar Coast Western Ghats India Brittonia 58 2 119 123 doi 10 1663 0007 196x 2006 58 119 ansocf 2 0 co 2 S2CID 32241023 Terrence Walters amp Roy Osborne eds 2004 Cycad Classification Concepts and Recommendations CABI publishing ISBN 0 85199 741 4 Retrieved from https en wikipedia org w index php title Cycas amp oldid 1123405843, wikipedia, wiki, book, books, library,

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