33-537: Cycas is a genus of cycad , and the only genus in the family Cycadaceae with all other genera of cycad being divided between the Stangeriaceae and Zamiaceae families. Cycas circinalis , a species endemic to India, was the first cycad species to be described in western literature, and is the type species of the genus. As of April 2024, there are 119 accepted species within the genus Cycas , all of which are native to Asia , Oceania, and eastern Africa and
66-658: A comparatively wide area including coastal regions of Mozambique , Tanzania , and Kenya in mainland Africa, extending to the Seychelles , Madagascar and Comoros islands in the Indian Ocean . In Oceania, Cycas species are native to Australia , Papua New Guinea , and the island nations of the Pacific Ocean region, but are absent from New Zealand . As in Asia, Cycas is the only genus of cycad found across
99-997: 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. Cycas take about 10 years to reach sexual maturity, after years of exclusive vegetative growth, which occurs by bulbils arising at
132-429: A number of differences between cycads and palms. For one, both male and female cycads are gymnosperms and bear cones (strobili), while palms are angiosperms and so flower and bear fruit. The mature foliage looks very similar between both groups, but the young emerging leaves of a cycad resemble a fiddlehead fern before they unfold and take their place in the rosette, while the leaves of palms are just small versions of
165-595: A stout and woody ( ligneous ) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious , that is, individual plants of a species are either male or female. Cycads vary in size from having trunks only a few centimeters to several meters tall. They typically grow slowly and have long lifespans. Because of their superficial resemblance to palms or ferns , they are sometimes mistaken for them, but they are not closely related to either group. Cycads are gymnosperms (naked-seeded), meaning their unfertilized seeds are open to
198-607: 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. Cycads were generally uncommon during the Permian. The two living cycad families are thought to have split from each other sometime between the Jurassic and Carboniferous. Cycads are thought to have reached their apex of diversity during
231-402: Is not well known, but as of April 2024, no accepted cycad species is known to be endemic to any of these three countries. In Africa, cycads belonging to all three cycad families are found making it a major center of diversity for cycads in general, but only one Cycas species ( Cycas thouarsii ) is native and it is restricted to eastern Africa and nearby island nations. C. thouarsii grows in
264-403: Is the accumulation of toxins in seeds and vegetative tissues; through horizontal gene transfer , cycads have acquired a family of genes ( fitD ) from a microbial organism, most likely a fungus, which gives them the ability to produce an insecticidal toxin. 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
297-516: The Yolngu in Australia's Arnhem Land as a source of food. They are harvested on their dry season to leach its poison under water overnight before ground into a paste, wrapped under bark and cooked on open fire until done. In Vanuatu , the cycad is known as namele and is an important symbol of traditional culture. It serves as a powerful taboo sign, and a pair of namele leaves appears on
330-506: The national flag and coat of arms. Together with the nanggaria plant, another symbol of Vanuatu culture, the namele also gives its name to Nagriamel , an indigenous political movement. Cycas clivicola Cycas clivicola is a species of cycad in Thailand , Cambodia , Vietnam , and Malaysia (including Perlis State Park). It is found on limestone outcrops, as well as on offshore islands. This cycad article
363-507: The stem-group of Cycas with confidence due to lacking the double vascular system that characterises the seeds of all living cycads. The leaf fossil genus Paracycas known from the Jurassic and Cretaceous of Europe has been suggested to be early representatives of the Cycas lineage by cladistic analysis. The plants are dioecious , and the family Cycadaceae is unique among the cycads in not forming seed cones on female plants, but rather
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#1732776461112396-511: The Indian ocean region, with the largest number of species native to Australia, China and Vietnam. In horticulture, the most widely grown and perhaps best-known Cycas species is Cycas revoluta , which is commercially grown in large numbers for sale as houseplants or to be used in landscaping. The majority of Cycas species are highly endangered. Many are threatened by the illegal trade of wild collected plants for plant collectors, and through
429-610: The Mesozoic. Although the Mesozoic is sometimes called the "Age of Cycads," some other groups of extinct seed plants with similar foliage, such as Bennettitales and Nilssoniales , that are not closely related, may have been more abundant. The oldest records of the modern genus Cycas are from the Paleogene of East Asia. Fossils assignable to Zamiaceae are known from the Cretaceous, with fossils assignable to living genera of
462-431: The air to be directly fertilized by pollination , as contrasted with angiosperms , which have enclosed seeds with more complex fertilization arrangements. Cycads have very specialized pollinators , usually a specific species of beetle . Both male and female cycads bear cones ( strobili ), somewhat similar to conifer cones . Cycads have been reported to fix nitrogen in association with various cyanobacteria living in
495-1763: The base of the trunk. Cycas species are threatened worldwide and almost all the species are listed in the IUCN Red List . Cycas beddomei is the only species of the genus Cycas listed in Appendix I of CITES. All other members of Cycadaceae are listed under Appendix II. Cycas rumphii and Cycas pectinata have the most widespread distribution. C. micholitzii Dyer C. multipinnata Chen & Yang C. pectinata Buchanan-Hamilton C. thouarsii Brown ex Gaudichaud-Beaupré C. revoluta Thunberg (Sago palm) C. taitungensis Shen et al. C. tropophylla Hill & Lôc C. ferruginea Wei C. curranii (Schuster) Hill C. debaoensis Zhong & Chen C. brachycantha Hill, Nguyên & Lôc C. immersa Craib C. bifida (Dyer) Hill C. szechuanensis Cheng & Fu C. wadei Merrill C. hainanensis Chen C. taiwaniana Carruthers C. fairylakea Wang C. circinalis L. (Indu) C. micronesica Hill C. pschannae Srivastava & Singh C. edentata de Laubenfels C. nitida Hill & Lindström C. rumphii Miquel C. clivicola Hill C. siamensis Miquel C. vespertilio Lindström & Hill C. riuminiana Porte ex Regel C. bougainvilleana Hill C. celebica Miquel C. macrocarpa Griffith C. nongnoochiae Hill C. elongata (Leandri) Wang Cycad Cycads / ˈ s aɪ k æ d z / are seed plants that typically have
528-752: The broader region, Cycas seemannii is found in Melanesia and western Polynesia and Cycas micronesica is found across Micronesia . Globally, some Cycas species are considered to be relatively widespread, for example Cycas thouarsii is native to a large area of mainland Africa and islands of the Indian Ocean, and Cycas pectinata and Cycas clivicola are both native to large areas of Asia; however, most Cycas species have restricted distributions, with some restricted to very small areas. In Asia, for example, more than 75% of species occur in no more than one country. For some countries, even though
561-418: The conversion of land for urban development or agricultural use. The genus Cycas is native to parts of Asia , eastern Africa and Oceania . Cycas has the widest distribution of any genus of cycad. In Asia, Cycas (and therefore, the family Cycadaceae) represent the only cycads native to Asia. Within Asia, Cycas species are native from India and Sri Lanka in the west, through China to Japan in
594-452: The diverse genus Encephalartos in southern and central Africa, and Macrozamia in Australia. Thus, the distribution pattern of cycad species with latitude appears to be an artifact of the geographical isolation of the remaining cycad genera and their species, and perhaps because they are partly xerophytic rather than simply tropical . Nuts of the Cycas orientis ( nyathu ) are coveted by
627-546: The early Carboniferous . Cycads Ginkgo Conifers Bennettitales Gnetales Angiosperms Cycads Ginkgo Conifers Gnetophytes (flowering plants) Cycas Dioon Macrozamia Lepidozamia Encephalartos Bowenia Ceratozamia Stangeria Zamia Microcycas Classification of the Cycadophyta to the rank of family. The following extinct cycad genera are known: The oldest probable cycad foliage
660-524: The extant cycads peaks at 17˚ 15"N and 28˚ 12"S, with a minor peak at the equator . There is therefore not a latitudinal diversity gradient towards the equator but towards the Tropic of Cancer and the Tropic of Capricorn . However, the peak near the northern tropic is largely due to Cycas in Asia and Zamia in the New World, whereas the peak near the southern tropic is due to Cycas again, and also to
693-1141: The family known from the Cenozoic. The living cycads are found across much of the subtropical and tropical parts of the world, with a few in temperate regions such as in Australia. The greatest diversity occurs in South and Central America . They are also found in Mexico , the Antilles , southeastern United States , Australia , Melanesia , Micronesia , Japan , China , Southeast Asia , Bangladesh , India , Sri Lanka , Madagascar , and southern and tropical Africa , where at least 65 species occur. Some can survive in harsh desert or semi-desert climates ( xerophytic ), others in wet rain forest conditions, and some in both. Some can grow in sand or even on rock , some in oxygen-poor, swampy, bog -like soils rich in organic material . Some are able to grow in full sun, some in full shade, and some in both. Some are salt tolerant ( halophytes ). Species diversity of
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#1732776461112726-556: The major evolutionary events behind the genesis of new species have taken place in Indochina and Australia, where the majority of living species are native. 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 and were assigned to the same family, Cycadaceae . A later study suggested that these seeds could not be assigned to
759-411: The mature frond. Another difference is in the stem . Both plants leave some scars on the stem below the rosette where there used to be leaves, but the scars of a cycad are helically arranged and small, while the scars of palms are a circle that wraps around the whole stem. The stems of cycads are also in general rougher and shorter than those of palms. The two extant families of cycads all belong to
792-676: The north east and through south east Asia (including the Philippines ) to Indonesia in the south. Globally, the northernmost species ( Cycas revoluta ) is found at 31°N in southern Japan. As of April 2024, the largest number of currently accepted species of Cycas in Asia are found in Vietnam (27 species), China (23 species), India (14 species), Thailand (12 species), Philippines (12 species) and Indonesia (10 species). The distribution of Cycas species in Myanmar , Laos , and Cambodia
825-471: The number of species may not be high, the level of species-specific genetic variation can be very high meaning that so that even countries with few species, it may contain distinct gene pools of widespread species. Cycas (and the Cycadaceae family) is considered as being an early offshoot that diverged early from all other living cycads (which belong to the family Zamiaceae ). Estimates of the timing of
858-654: The order Cycadales , and are the Cycadaceae and Zamiaceae (including Stangeriaceae ). These cycads have changed little since the Jurassic in comparison to some other plant divisions. Five additional families belonging to the Medullosales became extinct by the end of the Paleozoic Era. Based on genetic studies, cycads are thought to be more closely related to Ginkgo than to other living gymnosperms. Both are thought to have diverged from each other during
891-556: The region, with the exception for Australia, where cycads native to all three families of cycads are found. Despite this, Australia also has the largest number of Cycas species globally with 34 native Cycas species accepted (as of April 2024), including the southernmost species globally ( Cycas megacarpa ) found at 26°S in southeast Queensland . At least 7 Cycas species are found in Papua New Guinea , some of which are also found in parts of neighbouring Indonesia . In
924-467: The roots (the "coralloid" roots). These photosynthetic bacteria produce a neurotoxin called BMAA that is found in the seeds of cycads. This neurotoxin may enter a human food chain as the cycad seeds may be eaten directly as a source of flour by humans or by wild or feral animals such as bats, and humans may eat these animals. It is hypothesized that this is a source of some neurological diseases in humans. Another defence mechanism against herbivores
957-419: The same form on the leaflet as the leaflets do on the stalk. 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
990-688: The split ranging from the Jurassic to the Carboniferous . The earliest fossils assignable to Cycas are known from the Paleogene of East Asia, such as Cycas fushunensis from the Eocene (around 47.5 million years ago) of Northeast China with East Asia likely representing the ancestral homeland of the genus. The presence of Cycas in Australasia and eastern Africa is relatively new, but
1023-449: The stalk, perpendicular to it. The leaves are typically either compound (with leaflets emerging from the leaf stalk as "ribs"), or have edges ( margins ) so deeply cut ( incised ) so as to appear compound. The Australian genus Bowenia and some Asian species of Cycas, like Cycas multipinnata , C. micholitzii and C. debaoensis , have leaves that are bipinnate , the leaflets each having their own subleaflets, growing in
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1056-409: The top and center of the crown. The trunk may be buried, so the leaves appear to be emerging from the ground, so the plant appears to be a basal rosette . The leaves are generally large in proportion to the trunk size, and sometimes even larger than the trunk. The leaves are pinnate (in the form of bird feathers, pinnae ), with a central leaf stalk from which parallel "ribs" emerge from each side of
1089-414: The wild. Cycads have a cylindrical trunk which usually does not branch . However, some types of cycads, such as Cycas zeylanica , can branch their trunks. The apex of the stem is protected by modified leaves called cataphylls . Leaves grow directly from the trunk, and typically fall when older, leaving a crown of leaves at the top. The leaves grow in a rosette form, with new foliage emerging from
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