Cylindropuntieae
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Opuntioideae is a
subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...
of the
cactus A cactus (: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae (), a family of the order Caryophyllales comprising about 127 genera with some 1,750 known species. The word ''cactus'' derives, through Latin, ...
family,
Cactaceae A cactus (: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae (), a family of the order Caryophyllales comprising about 127 genera with some 1,750 known species. The word ''cactus'' derives, through Latin, ...
. It contains 15 genera divided into five
tribes The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...
. The subfamily encompasses roughly 220–250 species, and is geographically distributed throughout the
New World The term "New World" is used to describe the majority of lands of Earth's Western Hemisphere, particularly the Americas, and sometimes Oceania."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: ...
from
Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
, to
Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...
. Members of this subfamily have diverse
habits A habit (or wont, as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously. A 1903 paper in the ''American Journal of Psychology'' defined a "habit, from the standpoint of psychology, ...
, including small geophytes, hemispherical cushions, shrub">geophytes">...
, including small geophytes, hemispherical cushions, shrubs, trees, and columnar cacti consisting of indeterminate branches or determinate terete or spherical segments.


Description

Synapomorphies of Opuntioideae include small deciduous, barbed spines called glochids born on areoles and a bony
aril An aril (), also called arillus, is a specialized outgrowth from a seed that partly or completely covers the seed. An arillode, or false aril, is sometimes distinguished: whereas an aril grows from the attachment point of the seed to the ova ...
surrounding a campylotropous
ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the sporangium, megasporangium), ...
(inverted and curved, such that the micropyle almost meets the
funiculus Funiculus (''Latin'' for "slender rope") is any cord-like structure in anatomy or biology, and may refer to: Anatomy * the spermatic cord formed by the vas deferens and surrounding tissue * the umbilical cord attaching a fetus to the placenta dur ...
). Other prominent morphological characters for this subfamily are presence of cylindrical,
caducous Dehiscence is the splitting of a mature plant structure along a built-in line of weakness to release its contents. This is common among fruits, anthers and sporangia. Sometimes this involves the complete detachment of a part. Structures that op ...
leaves that tend to be shed by maturity and the sectioning of the stem into joints or pads known as
cladode Phylloclades and cladodes are flattened, photosynthesis, photosynthetic shoots, which are usually considered to be modified branches. The two terms are used either differently or interchangeably by different authors. ''Phyllocladus'', a genus of ...
s. Opuntioideae are unique among cacti for lacking in the stem a thick
cortex Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...
, an extensive system of cortical bundles, collapsible cortical cells, and medullary bundles. Typically, the
epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...
consists of a single layer of irregularly shaped cells, a cuticle at least 1-2 microns thick, and long, uniseriate
trichome Trichomes (; ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...
s in the areoles. Opuntioideae have a hypodermis of at least one layer, very thick walls, and druses (aggregations of calcium oxalate crystals), and their cortical cells have enlarged nuclei; the reason for this is unknown. They also possess
mucilage Mucilage is a thick gluey substance produced by nearly all plants and some microorganisms. These microorganisms include protists which use it for their locomotion, with the direction of their movement always opposite to that of the secretion of ...
cells. Notably, their lack of collapsible cortical cells, ribs, and
tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projectio ...
s mean that they cannot absorb water or transfer it intercellularly as easily as the other cacti, so this may place evolutionary constraints on the aridity of habitats and maximum adult size. One adaptation around this problem is the evolution of flattened cladodes that allow opuntioids to swell up with water, increasing in volume without an increase in surface area risking water loss. Opuntioids also lack fiber caps to their
phloem Phloem (, ) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is ...
bundles, which in other cacti protect against sucking insects and stiffen developing
internodes A stem is one of two main structural axes of a vascular plant, the other being the root. It supports leaves, flowers and fruits, transports water and dissolved substances between the roots and the shoots in the xylem and phloem, engages in pho ...
.


Taxonomy

A major challenge in Opuntioideae classification is that the subfamily is known to hybridize (particularly the Opuntieae tribe), which complicates identifying species. Genera exhibit variation in
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...
, which makes using genetic analysis more important in determining relationships, since physical characteristics used to define genera may be unseen in some of them. In 2009, a study by Griffith and Porter, based on ribosomal intergenic spacer analysis defined four clades within the Opuntioideae: # Core ''Maihueniopsis'' - which was shown as
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
through genetic analysis # ''Pterocactus'' - defined by a winged seed # Terete-stemmed - defined by cylinder-shaped stems # Flat-stemmed - defined by flat stems They noted that the boundaries of some genera as then
circumscribed In geometry, a circumscribed circle for a set of points is a circle passing through each of them. Such a circle is said to ''circumscribe'' the points or a polygon formed from them; such a polygon is said to be ''inscribed'' in the circle. * Circum ...
were unclear. Later research found different relationships based on what genetic sequences and analysis was used. In 2010, Nyffeler and Eggli, as part of a larger overhaul of Cactaceae systematics, proposed recognizing only Cylindropuntieae and Opuntieae as true tribes of Opuntioideae, since they were the tribes generally agreed to be monophyletic. All other genera would be placed in one
polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
basal group until further research produced more definitive answers to their phylogeny. A 2020 study using
chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...
genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...
sequences found a much clearer division into three
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
tribes. Their maximum likelihood cladogram is shown below (the genus ''Punotia'' was not included in the study). Other previously proposed tribes (Austrocylindropuntieae, Pterocacteae, and Pereskiopsideae) were found to be nested within these three tribes. Different relationships among the three tribes were found in other studies, so the authors of the 2020 study said that the relationship between the three tribes must be further investigated using other datasets.


Tribes and genera

The tribes and genera of the subfamily Opuntioideae are: Cylindropuntieae – round stems *''
Cylindropuntia ''Cylindropuntia'' is a genus of cacti (family (biology), family Cactaceae), containing species commonly known as chollas ( ), native to northern Mexico and the Southwestern United States. They are known for their barbed thorns, spines, and prick ...
'' (Engelm.) F.M.Knuth *'' Grusonia'' Rchb.f. ex Britton & Rose *'' Micropuntia'' Daston *''
Pereskiopsis ''Pereskiopsis'' is a genus of cactus (family (biology), family Cactaceae) in the subfamily Opuntioideae. Unlike typical cacti, it has persistent fleshy leaves. The genus name refers to its resemblance to the genus ''Pereskia''. Most species are ...
'' Britton & Rose *''
Quiabentia ''Quiabentia'' is a genus of cactus, cacti, closely related to ''Pereskiopsis''. Description The tree-like or bushy xerophytic species of the genus ''Quiabentia'' have whorled, fleshy, round branches that produce flat, fleshy leaves. The leaves a ...
'' Britton & Rose Opuntieae – flattened stems *'' Airampoa'' Frič (synonym ''Tunilla'') *''
Brasiliopuntia ''Brasiliopuntia'' is a genus in the cactus family, Cactaceae. It contains only one species, ''Brasiliopuntia brasiliensis''. Description ''Brasiliopuntia brasiliensis'' shows thin, upright, tree-like, slightly shrunken cladodes on a central, ...
'' (K. Schum.) A. Berger *'' Consolea'' Lem. *'' Miqueliopuntia'' Fric ex F. Ritter *''
Opuntia ''Opuntia'', commonly called the prickly pear cactus, is a genus of flowering plants in the cactus family Cactaceae, many known for their flavorful fruit and showy flowers. Cacti are native to the Americas, and are well adapted to arid clima ...
'' Mill. *''
Salmonopuntia ''Salmonopuntia'' is a South American genus of the cactus family (Cactus, Cactaceae). Species Species of the genus ''Salmonopuntia'' according to Plants of the World Online : References External links

* * Opuntioideae genera Opuntioidea ...
'' P.V.Heath *''
Tacinga ''Tacinga'' is a genus in the cactus family Cactus, Cactaceae, native to northeast Brazil (from northeast Minas Gerais to southern Rio Grande do Norte, including Bahia, Sergipe, Alagoas, Pernambuco and Paraíba). Once thought to be monotypic, the ...
'' Britton & Rose Tephrocacteae – round stems *''
Austrocylindropuntia ''Austrocylindropuntia'' is a genus of cactus, cacti (family (biology), family Cactaceae) with 11 recognized species, which were once included in the genus ''Opuntia''. Some are native to South America. Species External links Cactaceae: Member ...
'' Backeb. *'' Cumulopuntia'' F.Ritter *''
Maihueniopsis ''Maihueniopsis'' (from Greek ''opsis'', "view", referring to its resemblance to the unrelated '' Maihuenia'') is a genus of the cactus family (Cactaceae), containing 18 species. The former genus ''Puna'' R.Kiesling is now synonym to ''Maihueni ...
'' Speg. *'' Pterocactus'' K.Schum. *''
Punotia ''Punotia'' is a monotypic genus of flowering plants belonging to the family Cactaceae. The only species is ''Punotia lagopus''. Description ''Punotia lagopus'' grows in dense, large cushions up to over 1 meter in diameter and 60 centimeters high. ...
'' D.R.Hunt *''
Tephrocactus ''Tephrocactus'' (from Greek language, Greek ''tephra'', "ash", referring to the color of these plants' Epidermis (botany), epidermis) is a genus of the cactus family (Cactus, Cactaceae). Species Species of the genus ''Tephrocactus'' according t ...
'' Lem.


Intergeneric hybrids

* × ''Opulea'' (''Consolea'' × ''Opuntia'')


See also

* Taxonomy of the Cactaceae


References

{{Taxonbar, from=Q901099 Caryophyllales subfamilies