Cycad
Cycadales Temporal range:
| |
---|---|
Cycas rumphii with old and new male strobili. | |
Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Spermatophytes |
Clade: | Gymnospermae |
Division: | Cycadophyta Bessey 1907: 321.[2] |
Class: | Cycadopsida Brongn.[1] |
Order: | Cycadales Pers. ex Bercht. & J. Presl |
Extant groupings | |
| |
Synonyms | |
|
Cycads
Cycads are
Cycads have been reported to
Cycads all over the world are in decline, with four species on the brink of extinction and seven species having fewer than 100 plants left in the wild.[8]
Description
Cycads have a
The leaves are
Confusion with palms
Due to superficial similarities in foliage and plant structure, cycads and palms are often mistaken for each other. They also can occur in similar climates. However, they belong to different phyla and as such are not closely related. The similar structure is the product of convergent evolution.
Beyond those superficial resemblances, there are a number of differences between cycads and palms. For one, both male and female cycads are
Taxonomy
This article needs additional citations for verification. (November 2018) |
The two extant
Based on genetic studies, cycads are thought to be more closely related to Ginkgo than other living gymnosperms. Both are thought to have diverged from each other during the early Carboniferous.[13][14]
External phylogeny[13][14] | Internal phylogeny[15][16] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
Classification of the Cycadophyta to the rank of family.
- Class Cycadopsida Brongniart 1843
- Order Cycadales Persoon ex von Berchtold & Presl 1820
- Suborder Cycadineae Stevenson 1992
- Family CycadaceaePersoon 1807
- Genus Cycas
- Family
- Suborder Zamiineae Stevenson 1992
- Family Zamiaceae Horaninow 1834
- subfamily Diooideae Pilg. 1926
- Tribe Diooeae Schuster
- Genus Dioon
- Tribe Diooeae Schuster
- subfamily Zamioideae Stevenson 1992
- Tribe Encephalarteae Miquel 1861
- Genus Macrozamia
- Genus Lepidozamia
- Genus Encephalartos
- Tribe Zamieae Miquel 1861
- Genus Bowenia
- Genus Ceratozamia
- Genus Stangeria
- Genus Zamia
- Genus Microcycas
- Tribe Encephalarteae Miquel 1861
- subfamily Diooideae Pilg. 1926
- Family Zamiaceae Horaninow 1834
- Suborder Cycadineae Stevenson 1992
- Order Cycadales Persoon ex von Berchtold & Presl 1820
Fossil genera
The following extinct cycad genera are known:[17]
- Amuriella Late Jurassic, Russian Far East (leaf fragments)
- Androstrobus Triassic to Cretaceous, worldwide (leaf form genus)
- Antarcticycas Middle Triassic, Antarctica (known from the whole plant)[18]
- ?Anthrophyopsis Late Triassic, worldwide (leaf form genus, possibly a pteridospermatophyte)[19]
- Apoldia Triassic-Jurassic, Europe
- Archaeocycas Early Permian, Texas (leaf with sporophylls)
- Aricycas Late Triassic, Arizona (leaf form genus)
- Beania (=Sphaereda), Triassic to Jurassic, Europe & Central Asia (leaf form genus)
- Behuninia Late Jurassic, Colorado & Utah (fruiting structures)
- Bucklandia Middle Jurassic to Early Cretaceous, Europe and India (leaf form genus)
- Bureja Late Jurassic, Russia
- Cavamonocolpites Early Cretaceous, Brazil (pollen)
- Crossozamia Early to Late Permian, China (leaf form genus)
- Ctenis Mesozoic-Paleogene, Worldwide (leaf form genus)
- Ctenozamites Triassic-Cretaceous, worldwide (leaf form genus)
- Cycadenia Triassic, Pennsylvania (trunks)
- Cycadinorachis Late Jurassic, India (rachis)
- Fascisvarioxylon Late Jurassic, India (petrified wood)
- Gymnovulites, Latest Cretaceous/earliest Paleocene, India (seed)
- Heilungia, Late Jurassic to early Cretaceous, Russia & Alaska (leaf form genus)
- Leptocycas Late Triassic, North Carolina & China (known from the whole plant)[20]
- Mesosingeria, Jurassic to Early Cretaceous, Antarctica & Argentina (leaf form genus)
- Michelilloa, Late Triassic, Argentina (stem)
- ?Nikania, Early Cretaceous, Russia (leaf fragments)
- ?Nilssonia, Middle Permian to Late Cretaceous, worldwide (leaf form genus) (possibly not a cycad)[21]
- ?Nilssoniocladus, Early to Late Cretaceous, United States & Russia (stems, likely associated with Nilssonia, possibly deciduous)[22]
- Palaeozamia, Middle Jurassic, England
- Paracycas, Middle Jurassic to Late Jurassic, Europe and Central Asia
- ?Phasmatocycas, Late Carboniferous to Early Permian, Kansas, Texas & New Mexico (leaf with sporophylls)[23]
- Pleiotrichium, Late Cretaceous, Germany (leaf)
- Pseudoctenis, Late Permian to Late Cretaceous, worldwide (leaf form genus)
- Sarmatiella, Late Triassic, Ukraine
- Stangerites, Late Triassic to Early Jurassic, Virginia and Mexico (leaf form genus)
- Sueria, Early Cretaceous, Argentina (leaf)
- Taeniopteris, Carboniferous to Cretaceous, worldwide (polyphyletic leaf form genus, also includes bennettitales and marattiale ferns)
Fossil record
The oldest probable cycad foliage is known from the latest Carboniferous-Early Permian of South Korea and China, such as Crossozamia. Unambiguous fossils of cycads are known from the Early-Middle Permian onwards.[24] Cycads were generally uncommon during the Permian.[25] The two living cycad families are thought to have split from each other sometime between the Jurassic[15] and Carboniferous.[26] Cycads reached their apex of diversity during the Mesozoic. Although the Mesozoic is sometimes called the "Age of Cycads," the foliage of cycads is very similar to other groups of extinct seed plants, such as Bennettitales and Nilssoniales, that are not closely related, and cycads were probably only a minor component of mid-Mesozoic floras, with Bennettitales and Nilsonniales being more abundant than cycads.[27] The oldest records of the modern genus Cycas are from the Paleogene of East Asia.[28] Fossils assignable to Zamiaceae are known from the Cretaceous,[27] with fossils assignable to living genera of the family known from the Cenozoic.[16]
Distribution
The living cycads are found across much of the
Species diversity of the extant cycads peaks at 17˚ 15"N and 28˚ 12"S, with a minor peak at the
Cultural significance
In
See also
- Fossil Cycad National Monument, formerly in the U.S. state of South Dakota
References
- ^ Brongniart, A. (1843). Énumération des genres de plantes cultivées au Muséum d'histoire naturelle de Paris.
- ^ Bessey, C.E. (1907). "A synopsis of plant phyla". Nebraska Univ. Stud. 7: 275–373.
- ^ Dehgan, Bijan (1983). "Propagation and Growth of Cycads—A Conservation Strategy". Proceedings of the Florida State Horticultural Society. 96: 137–139 – via Florida Online Journals.
- PMID 33862930.
- PMID 22382274.
- PMID 26791617.
- PMID 35437001.
- ^ Davis, Judi (27 June 2018). "Meet Durban's famous cycad family". South Coast Herald. Retrieved 11 September 2022.
- PMID 30551676.
- ^ Rutherford, Catherine. CITES and Cycads: A User's Guide (PDF). Royal Botanic Gardens, Kew.
- ISBN 9781300654537.
- ISBN 978-1-4000-5036-9.
- ^ PMID 23315384.
- ^ S2CID 236141481.
- ^ S2CID 206535984.
- ^ S2CID 14815027.
- ^ "PBDB". paleobiodb.org. Retrieved 16 March 2024.
- .
- ISSN 0034-6667.
- .
- S2CID 3604369.
- ISSN 0034-6667.
- ISSN 0002-9122.
- S2CID 233860955.
- S2CID 249627815.
- PMID 37302411.
- ^ PMID 28388891.
- PMID 34520529.
- ^ Orchard, A.E. & McCarthy, P.M. (eds.) (1998). Flora of Australia 48: 1-766. Australian Government Publishing Service, Canberra.
- ^ National Recovery Plan for the MacDonnell Ranges Cycad Macrozamia macdonnellii (PDF) (Report). Department of Natural Resources, Environment, The Arts and Sport, Northern Territory. Retrieved 16 July 2015.
- ISBN 9780226044682.
- ^ "Macrozamia communis", The IUCN Red List of Threatened Species
- ^ Dan McGarry (9 April 2018). "A Princely Title". Vanuatu Daily Post.
External links
- "Palm Trees, Small Palms, Cycads, Bromeliads and tropical plants". Archived from the original on 20 May 2014. Site with thousands of large, high quality photos of cycads and associated flora. Includes information on habitat and cultivation. (Site is dead.)
- "The Cycad Pages". Royal Botanic Gardens Sydney. Archived from the original on 29 March 2021.
- "Gymnosperm Database: Cycads". Archived from the original on 10 August 2010.
- "Fairchild Tropical Botanic Garden". Archived from the original on 23 February 2015. One of the largest collections of cycads in the world in Florida, U.S.A.
- "Main Page". Palm and Cycad Societies of Australia (PACSOA). Retrieved 18 June 2023.
- "Welcome". The Cycad Society of South Africa. Retrieved 18 June 2023.
- David Dalton (1997). "Part I. The range of organisms that can fix nitrogen". Nitrogen Fixation. Retrieved 18 June 2023. Cycad nitrogen fixation
- "Cycad toxicity". The Cycad Pages. Royal Botanic Gardens Sydney. Archived from the original on 17 July 2020.
- Lauren Kessler (28 August 2005). "The Cult of the Cycads". The New York Times Magazine. Archived from the original on 4 June 2022. Magazine article on cycad collectorship and cycad smuggling.