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:''For the insect, see
Cicada The cicadas () are a superfamily, the Cicadoidea, of insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects ha ...

Cicada
.'' Cycads are
seed plant The spermatophytes, also known as phanerogams (taxon Phanerogamae) or phaenogams (taxon Phaenogamae), comprise those plants that produce seeds, hence the alternative name seed plants. They are a subset of the embryophytes or land plants. The t ...
s that typically have a stout and woody (
ligneous A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposite to Herbaceous plant, herbaceous plants that die back to th ...
) trunk with a
crown '' File:서봉총 금관 금제드리개.jpg, The Seobongchong Golden Crown of Ancient Silla, which is 339th National Treasure of South Korea. It is basically following the standard type of Silla's Crown. It was excavated by Swedish Crown Pri ...
of large, hard, stiff,
evergreen In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Anci ...

evergreen
and (usually)
pinnate Pinnation (also called pennation) is the arrangement of feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on dinosaurs, both avian (bird) and some non-avian (non-bird) and possibly other archosaur ...
leaves. The species are
dioecious Dioecy (; Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as o ...
, 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 very slowly and live very long, with some specimens known to be as much as 1,000 years old. Because of their superficial resemblance, they are sometimes mistaken for
palms
palms
or
fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses and other bryophytes by being vascular, ...

fern
s, but they are not closely related to either group. Cycads are
gymnosperms The gymnosperms, also known as Acrogymnospermae, are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes. The term "gymnosperm" comes from the composite word in el, γυμνόσπερμος ( el, γ ...
(naked seeded), meaning their
unfertilized
unfertilized
seeds are open to the air to be directly fertilized by
pollination Pollination is the transfer of pollen from an anther (male part) of a plant to the stigma (female part) of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by Anemophily, wind. Pollinating agents are a ...

pollination
, as contrasted with
angiosperms Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλά ...
, which have enclosed seeds with more complex fertilization arrangements. Cycads have very specialized
pollinator A pollinator is an animal that moves pollen File:Pollen Tube.svg, Pollen Tube Diagram Pollen is a powdery substance consisting of pollen grains which are Sporophyte, microsporophytes of spermatophyta, seed plants, which produce male gametes ...

pollinator
s, usually a specific species of
beetle Beetles are a group of insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome ...

beetle
. Both male and female cycads bear cones (
strobili A strobilus (plural: strobili) is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem. Strobili are often called cones, but some botanists restrict the use of the term cone to t ...
), somewhat similar to
conifer cone (''Pinus coulteri'') cone, the heaviest pine cone A conifer cone (in formal botany, botanical usage: strobilus A strobilus (plural: strobili) is a structure present on many land plant Plants are mainly multicellular organisms, predomi ...
s. Cycads have been reported to fix nitrogen in association with various
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum (biology), phylum of Gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), giving them their other name, "blue-green algae", t ...

cyanobacteria
living in the roots (the "coralloid" roots). These photosynthetic bacteria produce a
neurotoxin Neurotoxins are toxins that are destructive to nervous tissue, nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insult (medical), insultsSpencer 2000 that can adversely affect function in ...
called
BMAA β-Methylamino--alanine, or BMAA, is a non-proteinogenic amino acid In biochemistry Biochemistry or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and bio ...
that is found in the
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positiv ...

seed
s 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 disease A neurological disorder is any Disorder (medicine)#Disorder, disorder of the nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord or other nerves can result in a range of symptoms. Examples of symptoms inclu ...
s in humans. 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. The plant has a very long fossil history, with evidence that they existed in greater abundance and in greater diversity before the Jurassic and late Triassic mass extinction events.


Description

Cycads have a
cylindrical A cylinder (from ) has traditionally been a Solid geometry, three-dimensional solid, one of the most basic of curvilinear geometric shapes. Geometrically, it can be considered as a Prism (geometry), prism with a circle as its base. This traditio ...
trunk which usually does not
branch The branches and leaves of a tree. A branch ( or , ) or tree branch (sometimes referred to in botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or ...

branch
. But, some types of Cycads can branch their trunks, at their adult age. (Eg: ''Cycas Zeylanica'' is an endemic Cycad found in Sri Lanka, which can branch their trunk.) 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 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 Pinnation (also called pennation) is the arrangement of feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on dinosaurs, both avian (bird) and some non-avian (non-bird) and possibly other archosaur ...
(in the form of bird feathers,
pinnae The auricle or auricula is the visible part of the ear that is outside the head. It is also called the pinna (Latin for "wing" or "fin", plural pinnae), a term that is used more in zoology. Structure The diagram shows the shape and location of m ...
), with a central leaf stalk from which parallel "ribs" emerge from each side of the stalk, perpendicular to it. The leaves are typically either compound (the leaf stalk has
leaflets Leaflet may refer to: * Leaflet (botany), part of a compound leaf * Leaflet (software), a Javascript library * Pamphlet, a type of publication ** Folded leaflet ** Flyer (pamphlet) ** Airborne leaflet propaganda * Cusps of heart valves, also known a ...
emerging from it as "ribs"), or have edges ( margins) so deeply cut ( incised) so as to appear compound. Some species have leaves that are
bipinnate The following is a defined list of terms which are used to describe leaf plant morphology, morphology in the description and taxonomy (biology), taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leafl ...
, which means the leaflets each have their own subleaflets, growing in the same form on the leaflet as the leaflets grow on the stalk of the leaf (
self-similar geometry
self-similar geometry
).


Confusion with palms

Due to superficial similarities in foliage and plant structure, cycads and
palms
palms
are often mistaken for each other. They also can occur in similar climates. However, they belong to completely different phyla and are not closely related at all. The similar structure is evidence of
convergent evolution Convergent evolution is the independent evolution Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; eithe ...
. Beyond those superficial resemblances, there are a number of differences between cycads and palms. For one, both male and female cycads are
gymnosperm The gymnosperms ( Greek language, lit. revealed seeds) are a group of Spermatophyte, seed-producing plants that includes Pinophyta, conifers, cycads, ''Ginkgo'', and gnetophyta, gnetophytes, forming the clade Gymnospermae, the living members of ...
s and bear cones (strobili), while palms are
angiosperm The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of land plants, with 64 orders, 416 families, approximately 13,000 known genera and 300,000 known species In biology, a species is the ...

angiosperm
s 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 Fiddlehead sculpture at the Saint John Arts Centre by sculptor Jim Boyd in Saint John, New Brunswick, Canada Fiddleheads or fiddlehead greens are the furled fronds of a young fern, harvested for use as a vegetable. Left on the plant, each ...
before they unfold and take their place in the rosette, while the leaves of palms are never coiled up and instead are just small versions of the mature frond. Another difference is in the
stem Stem or STEM may refer to: Biology * Plant stem '' has lost its leaves, but is producing adventitious roots from the nodes. A stem is one of two main structural axes of a vascular plant, the other being the root In vascular plants, the roo ...

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.


Taxonomy

The three extant
families In human society, family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of families is to maintain the w ...
of cycads all belong to the order
Cycadales
Cycadales
, and are
Cycadaceae ''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 perennial plant, perennials which achieved their maxim ...
,
Stangeriaceae Stangeriaceae is the smallest family of the cycads, including only two extant genera, ''Stangeria'' and ''Bowenia.'' Taxonomy Although the family was first published by Andreas Franz Wilhelm Schimper, Schimper and August Schenk, Schenk as Stanger ...
, and
Zamiaceae The Zamiaceae are a family of cycad :''For the insect, see Cicada.'' Cycads are seed plants with a very long fossil history that were formerly more abundant and more diverse than they are today. They typically have a stout and woody (ligneou ...
. These cycads have changed little since the Jurassic, compared to some major evolutionary changes in other plant divisions. Five additional families belonging to the
Medullosales The Medullosales is an extinct order of pteridospermous seed plants characterised by large ovules with circular cross-section and a vascularised nucellus, complex pollen-organs, stems and rachides with a dissected stele A stele ( ),Angli ...
became extinct by the end of the Paleozoic Era. Based on genetic studies, cycads are thought to be more closely related to ''
Ginkgo ''Ginkgo'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. ...

Ginkgo
'' than other living gymnosperms. Classification of the Cycadophyta to the rank of family. ;Class Cycadopsida ;;Order Cycadales ;;;Suborder Cycadineae ;;:Family
Cycadaceae ''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 perennial plant, perennials which achieved their maxim ...
;;;Suborder Zamiineae ;;:Family
Stangeriaceae Stangeriaceae is the smallest family of the cycads, including only two extant genera, ''Stangeria'' and ''Bowenia.'' Taxonomy Although the family was first published by Andreas Franz Wilhelm Schimper, Schimper and August Schenk, Schenk as Stanger ...
;;:Family
Zamiaceae The Zamiaceae are a family of cycad :''For the insect, see Cicada.'' Cycads are seed plants with a very long fossil history that were formerly more abundant and more diverse than they are today. They typically have a stout and woody (ligneou ...
Relationships between the extant genera, according to Nagalingum ''et al''. (2011):


Fossil record

The probable former range of cycads can be inferred from their global distribution. For example, the family Stangeriaceae only contains three extant species in Africa and Australia. Diverse fossils of this family have been dated to 135 mya, indicating that diversity may have been much greater before the Jurassic and late Triassic mass extinction events. However, the cycad fossil record is generally poor and little can be deduced about the effects of each mass extinction event on their diversity. Instead, correlations can be made between the number of extant
gymnosperms The gymnosperms, also known as Acrogymnospermae, are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes. The term "gymnosperm" comes from the composite word in el, γυμνόσπερμος ( el, γ ...
and
angiosperms Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλά ...
. It is likely that cycad diversity was affected more by the great angiosperm radiation in the mid-Cretaceous than by extinctions. Very slow cambial growth was first used to define cycads, and because of this characteristic the group could not compete with the rapidly growing, relatively short-lived angiosperms, which now number over 250,000 species, compared to the 1080 remaining gymnosperms.


Origins

The cycad fossil record dates to the early
Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous period million years ago (Mya), to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleo ...
, ( mya). There is controversy over older cycad fossils that date to the late
Carboniferous The Carboniferous ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisi ...
period, . This
clade A clade (), also known as a monophyletic group or natural group, is a group of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell t ...

clade
probably diversified extensively within its first few million years, although the extent to which it radiated is unknown because relatively few fossil specimens have been found. The regions to which cycads are restricted probably indicate their former distribution in the
Pangea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology) ...

Pangea
supercontinent before the supercontinents
Laurasia Laurasia (), a portmanteau A portmanteau (, ) or portmanteau word (from "Portmanteau (luggage), portmanteau") is a Blend word, blend of words
and
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (ge ...

Gondwana
separated. Recent studies have indicated the common perception of existing cycad species as
living fossil A living fossil is an extant taxon that cosmetically resembles ancestral species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living foss ...
s is largely misplaced, with only ''
Bowenia The genus ''Bowenia'' includes two extant taxa, living and two fossil species of cycads in the family Stangeriaceae, sometimes placed in their own family Boweniaceae. They are entirely restricted to Australia. The two living species occur in Quee ...
'' dating to the
Cretaceous The Cretaceous ( ) is a geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisions ...

Cretaceous
or earlier. Although the cycad lineage itself is ancient, most extant species have evolved in the last 12 million years. Though 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 Bennettitales (also known as cycadeoids) is an extinct Order (biology), order of Spermatophyte, seed plants that first appeared in the Permian period and became extinct in most areas toward the end of the Cretaceous. Bennettitales are among the mo ...
and Nilssoniales, that are not closely related, and cycads were probably only a minor component of mid-Mesozoic floras. The
family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the same spatial or social territory, typically subject to the same Politics, ...
Stangeriaceae Stangeriaceae is the smallest family of the cycads, including only two extant genera, ''Stangeria'' and ''Bowenia.'' Taxonomy Although the family was first published by Andreas Franz Wilhelm Schimper, Schimper and August Schenk, Schenk as Stanger ...
(named for Dr. William Stanger, 1811–1854), consisting of only three
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, s ...
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
, is thought to be of Gondwanan origin, as fossils have been found in
Lower Cretaceous Lower may refer to: *Lower (surname)Lower is a surname. Notable people with the surname include: * Arthur R. M. Lower (1889–1988) Canadian historian * Britt Lower (born 1985), American actress * Cyrus B. Lower (1843–1924), American Civil War ...
deposits in
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country located mostly in the southern half of South America. Sharing the bulk of the Southern Cone with Chile to the west, the country is also bordered b ...

Argentina
, dating to . The family
Zamiaceae The Zamiaceae are a family of cycad :''For the insect, see Cicada.'' Cycads are seed plants with a very long fossil history that were formerly more abundant and more diverse than they are today. They typically have a stout and woody (ligneou ...
is more diverse, with a fossil record extending from the middle
Triassic The Triassic ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisions int ...

Triassic
to the
Eocene The Eocene ( ) Epoch is a geological epoch In chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the modern science of chronology Chronology (from Latin Latin (, or , ) is a classical language belonging to the ...
() in
North North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to East and West. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology The ...

North
and South America,
Europe Europe is a continent A continent is one of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven regions are commonly regarded as continents. Ordered from largest ...

Europe
, Australia, and
Antarctic The Antarctic (US English or , UK English or and or ) is a polar region The polar regions, also called the frigid zones, of Earth are the regions of the planet that surround its geographical poles (the North North is one of t ...

Antarctic
a, implying the family was present before the break-up of Pangea. The family
Cycadaceae ''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 perennial plant, perennials which achieved their maxim ...
is thought to be an early offshoot from other cycads, with fossils from
Eocene The Eocene ( ) Epoch is a geological epoch In chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the modern science of chronology Chronology (from Latin Latin (, or , ) is a classical language belonging to the ...
deposits () in
Japan , image_flag = Flag of Japan.svg , alt_flag = Centered deep red circle on a white rectangle , image_coat = Imperial Seal of Japan.svg , alt_coat = Golden circle subdiv ...

Japan
,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the List of countries and dependencies by population, world's most populous country, with a population of around 1.4 billion. Covering approximately 9.6& ...

China
, and
North America North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be described as the northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to ...

North America
, indicating this family originated in Laurasia. ''
Cycas ''Cycas'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a spe ...

Cycas
'' is the only
genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biolog ...
in the family and contains 99 species, the most of any cycad genus.
Molecular A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atom An atom is the smallest unit of ordinary matter In ...
data have recently shown ''Cycas'' species in
Australasia Australasia is a region In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets. The ...

Australasia
and the east coast of Africa are recent arrivals, suggesting
adaptive radiation In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic inte ...
may have occurred. The current distribution of cycads may be due to radiations from a few ancestral types sequestered on Laurasia and Gondwana, or could be explained by
genetic drift Genetic drift (allelic drift or the Sewall Wright effect) is the change in the frequency of an existing gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_inheritance#History, Me ...

genetic drift
following the separation of already evolved genera. Both explanations account for the strict
endemism Endemism is the state of a species being native to a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...
across present continental lines.


Distribution

The living cycads are found across much of the
subtropical The subtropical zones or subtropics are geographical and climate zones located to the north and south of the Torrid Zone ''Torrid Zone'' is a 1940 adventure film Adventure films are a genre of film whose plots feature elements of travel. ...

subtropical
and
tropical The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S; these latitudes correspond to ...

tropical
parts of the world. The greatest diversity occurs in
South South is one of the cardinal directions or compass points. South is the opposite of north and is perpendicular to the east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earlier Proto-Germanic language, Proto-Germa ...

South
and
Central America Central America ( es, América Central, , ''Centroamérica'' ) is a region of the Americas. It is bordered by Mexico to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. Central America consist ...

Central America
. They are also found in
Mexico Mexico ( es, México ; Nahuan languages: ), officially the United Mexican States (; EUM ), is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; ...

Mexico
, the
Antilles The Antilles (; gcf, label=Antillean Creole, Antiy; es, Antillas; french: Antilles; nl, Antillen; gcf, label=Antillean Creole, Antiy; ht, Antiy; pap, Antias; Jamaican Patois: ''Antiliiz'') is an archipelago bordered by the Caribbean Sea to ...

Antilles
, southeastern
United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country Contiguous United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal di ...

United States
,
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, smal ...

Australia
,
Melanesia Melanesia (, ) is a subregion of Oceania in the southwestern Pacific Ocean. It extends from the island of New Guinea in the west to Tonga in the east, and includes the Arafura Sea. The region includes the four independent countries of Fiji, V ...

Melanesia
,
Micronesia Micronesia (, ; from grc, μικρός ''mikrós'' "small" and ''nêsos'' "island") is a subregion of Oceania, consisting of thousands of small islands in the western Pacific Ocean. It has a close shared cultural history with three other isl ...

Micronesia
,
Japan , image_flag = Flag of Japan.svg , alt_flag = Centered deep red circle on a white rectangle , image_coat = Imperial Seal of Japan.svg , alt_coat = Golden circle subdiv ...

Japan
,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the List of countries and dependencies by population, world's most populous country, with a population of around 1.4 billion. Covering approximately 9.6& ...

China
,
Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia or SEA, is the geographical southeastern subregion of Asia, consisting of the regions that are south of China, south-east of the Indian sub ...

Southeast Asia
,
India India (Hindi: ), officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by population, second-most populous country, the List of countries and dependencies by area, seventh-largest ...

India
,
Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකාව, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon, and officially the Democratic Socialist Republic of Sri Lanka, is ...

Sri Lanka
,
Madagascar Madagascar (; mg, Madagasikara), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), and previously known as the Malagasy Republic, is an island country in the Indian Ocean, a ...

Madagascar
, and
southern The name Southern may refer to: * South South is one of the cardinal directions or compass points. South is the opposite of north and is perpendicular to the east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earl ...
and tropical
Africa Africa is the world's second-largest and second-most populous continent A continent is one of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven regions are ...

Africa
, where at least 65
species In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...

species
occur. Some can survive in harsh
desert upright=1.5, alt=see caption, Sand dunes in the Rub' al Khali ("Empty quarter") in the United Arab Emirates">Rub'_al_Khali.html" ;"title="Sand dunes in the Rub' al Khali">Sand dunes in the Rub' al Khali ("Empty quarter") in the United Arab ...

desert
or semi-desert
climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...

climate
s (
xerophytic A xerophyte (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...
), others in wet
rain forest Rainforests are forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing and ecological func ...

rain forest
conditions, and some in both. Some can grow in
sand Sand is a granular Granularity (also called graininess), the condition of existing in granules or grains A grain is a small, hard, dry seed A seed is an embryonic plant enclosed in a protective outer covering. The formation of th ...

sand
or even on
rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the way in w ...
, some in oxygen-poor, swampy,
bog A bog or bogland is a wetland A wetland is a distinct ecosystem that is flooded by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (Anoxic waters, anoxic) processes pr ...

bog
-like soils rich in
organic material Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial and aquatic environments. It is matter In classical physics and general chem ...
. Some are able to grow in full sun, some in full shade, and some in both. Some are
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mineral is known as rock salt or halite. Sa ...
tolerant (
halophyte Image:Spartina alterniflora.jpg, 250px, ''Spartina alterniflora'' (cordgrass), a halophyte. A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spr ...
s). Species diversity of the extant cycads peaks at 17˚ 15"N and 28˚ 12"S, with a minor peak at the
equator The Earth's equator is an imaginary planetary line that is about long in circumference. The equator divides the planet into the Northern Hemisphere and Southern Hemisphere and is located at 0 degrees latitude In geography, latitude is ...

equator
. There is therefore not a latitudinal diversity gradient towards the equator but towards the
Tropic of Cancer The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted t ...

Tropic of Cancer
and the
Tropic of Capricorn The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point at the December (or southern) solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reaches ...
. 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 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 A xerophyte (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...
rather than simply
tropical The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S; these latitudes correspond to ...

tropical
. Notes: The distribution area on the map should be expanded to include the range of ''Macrozamia macdonnelliana'' in the central region of Australia, ''Zamia boliviana'' in Bolivia and Mato Grosso, Brazil, ''Cycas thouarsii'' on Comoros and Seychelles, and ''Cycas micronesica'' on the islands of Guam, Palau, Rota, & Yap. Also, the depiction of cycad distribution in Africa, particularly the western boundary, should be improved to show the actual range limits, rather than national borders.


Cultural significance

In
Vanuatu Vanuatu ( or ; ), officially the Republic of Vanuatu (french: link=no, République de Vanuatu; Bislama Bislama (; ; also known by its earlier French name, ) is a creole language, and one of the official languages of Vanuatu. It is the fir ...

Vanuatu
, the cycad is known as ''namele'' and is an important symbol of traditional culture. It serves as a powerful
taboo A taboo is an implicit prohibition on something (usually against an utterance or behavior) based on a cultural sense that it is excessively repulsive or, perhaps, too sacred for ordinary people.''Encyclopædia Britannica Online''.Taboo. Encyclopæ ...

taboo
sign, and a pair of ''namele'' leaves appears on the
national flag A national flag is a flag that represents and symbolizes a given nation. It is Fly (flag), flown by the government of that nation, but usually can also be flown by its citizens. A national flag is typically designed with specific meanings for its ...

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.


See also

*Fossil Cycad National Monument, formerly in the U.S. state of South Dakota


References


External links


Palm Trees, Small Palms, Cycads, Bromeliads and tropical plants
site with thousands of large, high quality photos of cycads and associated flora. Includes information on habitat and cultivation. *Hill KD (1998–2004) The Cycad Pages, Royal Botanic Gardens Sydney. http://plantnet.rbgsyd.nsw.gov.au/PlantNet/cycad/index.html



* [http://www.pacsoa.org.au/ Palm and Cycad Societies of Australia (PACSOA)]
The Cycad Society of South Africa






''The New York Times'' Magazine article on cycad collectorship and cycad smuggling {{Taxonbar, from1=Q1089795, from2=Q157114, from3=Q5197912, from4=Q5605610 Cycads, Dioecious plants Cisuralian first appearances Extant Permian first appearances