Dioon
Encyclopedia
Dioon is a genus
of cycad
s in the family Zamiaceae
. It contains 11 accepted species
that are native to Mexico
, Honduras
, and Nicaragua
. Their habitats include tropical forests, pine-oak forest
, and dry hillsides, canyons and coastal dunes.
Dioons are dioecious
, palmlike shrubs with cylindrical stems, usually with many leaves. Leaf bases are persistent or shedding to leave smooth bark. The genus is commonly divided into two groups of distinct morphology. The first includes D. mejiae
, D. rzedowskii, and D. spinulosum
, which are characterized by the greater size of their fronds, trunks, and cones. The second group contains D. califanoi, D. caputoi, D. edule
, D. holmgrenii, D. merolae, D. purpusii
, D. sonorense, and D. tomasellii, which are smaller overall, with shorter trunks, much shorter fronds, and smaller cones.
The leaves
are pinnate, spirally arranged, interspersed with cataphyll
s, with leaflets not articulated and lacking a midrib. The lower leaflets are often reduced to spines. The sporophyll
s are not in vertical rows in cones, and the megasporophyll apices are broadly flattened, upturned, and overlapping.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of cycad
Cycad
Cycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...
s in the family Zamiaceae
Zamiaceae
The Zamiaceae are a family of cycads that are superficially palm or fern-like. They are divided into two subfamilies with eight genera and about 150 species in the tropical and warm temperate regions of Africa, Australia and North and South America....
. It contains 11 accepted species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
that are native to Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, Honduras
Honduras
Honduras is a republic in Central America. It was previously known as Spanish Honduras to differentiate it from British Honduras, which became the modern-day state of Belize...
, and Nicaragua
Nicaragua
Nicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...
. Their habitats include tropical forests, pine-oak forest
Tropical and subtropical coniferous forests
Tropical and subtropical coniferous forests are a forest biome. They are located in regions of semi-humid climate at tropical and subtropical latitudes. Most tropical and subtropical coniferous forest ecoregions are found in the Nearctic and Neotropic ecozones, from Mexico to Nicaragua and on the...
, and dry hillsides, canyons and coastal dunes.
Dioons are dioecious
Dioecious
Dioecy is the property of a group of biological organisms that have males and females, but not members that have organs of both sexes at the same time. I.e., those whose individual members can usually produce only one type of gamete; each individual organism is thus distinctly female or male...
, palmlike shrubs with cylindrical stems, usually with many leaves. Leaf bases are persistent or shedding to leave smooth bark. The genus is commonly divided into two groups of distinct morphology. The first includes D. mejiae
Dioon mejiae
Dioon mejiae is a species of cycad that is native to Honduras and Nicaragua. Common names include palma teosinte, teocinte, teocinta , teocintle, teocsinte, teosinte, tiusinte, and tusinte, all of which mean "sacred ear.-External links:...
, D. rzedowskii, and D. spinulosum
Dioon spinulosum
Dioon spinulosum, giant dioon, or gum palm, is a cycad endemic to limestone cliffs and rocky hillsides in the tropical rainforests of Veracruz and Oaxaca, Mexico. It is one of the tallest cycads in the world, growing to 12m in height. The tree is found at low elevations to 300 m above sea...
, which are characterized by the greater size of their fronds, trunks, and cones. The second group contains D. califanoi, D. caputoi, D. edule
Dioon edule
Dioon edule is a cycad native to Mexico, also known as palma de la Virgen.Two subspecies are known*Dioon edule subsp. angustifolium*Dioon edule subsp. edule- Dioon Edule var. Edule :...
, D. holmgrenii, D. merolae, D. purpusii
Dioon purpusii
Dioon purpusii is a cycad tree endemic to a very small region in Mexico .-Name:The epithet purpusii, chosen by Joseph Nelson Rose, is an homage to one of Rose's contemporaries, colleague Carl Albert Purpus Dioon purpusii (Purpus' cycad) is a cycad tree endemic to a very small region in Mexico...
, D. sonorense, and D. tomasellii, which are smaller overall, with shorter trunks, much shorter fronds, and smaller cones.
The leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
are pinnate, spirally arranged, interspersed with cataphyll
Cataphyll
In plant morphology, a cataphyll is a leaf whose primary function is something other than photosynthesis...
s, with leaflets not articulated and lacking a midrib. The lower leaflets are often reduced to spines. The sporophyll
Sporophyll
A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls bear either megasporangia , or microsporangia...
s are not in vertical rows in cones, and the megasporophyll apices are broadly flattened, upturned, and overlapping.
Accepted species
- Dioon califanoi De Luca & Sabato
- Dioon caputoi De Luca et al.
- Dioon eduleDioon eduleDioon edule is a cycad native to Mexico, also known as palma de la Virgen.Two subspecies are known*Dioon edule subsp. angustifolium*Dioon edule subsp. edule- Dioon Edule var. Edule :...
Lindl. - Dioon holmgrenii De Luca et al.
- Dioon mejiaeDioon mejiaeDioon mejiae is a species of cycad that is native to Honduras and Nicaragua. Common names include palma teosinte, teocinte, teocinta , teocintle, teocsinte, teosinte, tiusinte, and tusinte, all of which mean "sacred ear.-External links:...
Standl. & L.O.Williams - Dioon merolae De Luca et al.
- Dioon purpusiiDioon purpusiiDioon purpusii is a cycad tree endemic to a very small region in Mexico .-Name:The epithet purpusii, chosen by Joseph Nelson Rose, is an homage to one of Rose's contemporaries, colleague Carl Albert Purpus Dioon purpusii (Purpus' cycad) is a cycad tree endemic to a very small region in Mexico...
Rose - Dioon rzedowskii De Luca et al.
- Dioon sonorense (De Luca et al.) Chemnick et al.
- Dioon spinulosumDioon spinulosumDioon spinulosum, giant dioon, or gum palm, is a cycad endemic to limestone cliffs and rocky hillsides in the tropical rainforests of Veracruz and Oaxaca, Mexico. It is one of the tallest cycads in the world, growing to 12m in height. The tree is found at low elevations to 300 m above sea...
Dyer - Dioon tomasellii De Luca et al.
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