In 1984, the International Organization for Succulent Plant Study set up a working party, now called the International Cactaceae Systematics Group, to produce a consensus classification of the cactus family, down to the level of genus . Their classification has been used as the basis for systems published since the mid-1990s. Treatments in the 21st century have generally divided the family into around 125–130 genera and 1,400–1,500 species, which are then arranged in a number of tribes and subfamilies . However, subsequent molecular phylogenetic studies have shown that a very high proportion of the higher taxa (genera, tribes and subfamilies) are not monophyletic , i.e. they do not contain all of the descendants of a common ancestor. As of August 2023 , the internal classification of the family Cactaceae remained uncertain and subject to change. A classification incorporating many of the insights from the molecular studies was produced by Nyffeler and Eggli in 2010.
20-721: Cylindropuntieae Opuntieae Pterocacteae Tephrocacteae Opuntioideae is a subfamily of the cactus family, Cactaceae . It contains 15 genera divided into five tribes . The subfamily encompasses roughly 220–250 species, and is geographically distributed throughout the New World from Canada , to Argentina . Members of this subfamily have diverse habits , including small geophytes , hemispherical cushions, shrubs , trees, and columnar cacti consisting of indeterminate branches or determinate terete or spherical segments. Synapomorphies of Opuntioideae include small deciduous, barbed spines called glochids born on areoles and
40-403: A bony aril surrounding a campylotropous ovule (inverted and curved, such that the micropyle almost meets the funiculus ). Other prominent morphological characters for this subfamily are presence of cylindrical, caducous leaves that tend to be shed by maturity and the sectioning of the stem into joints or pads known as cladodes . Opuntioideae are unique among cacti for lacking in the stem
60-663: A single genus, Calymmanthium . Of the remaining eight, only two ( Cacteae and Rhipsalideae ) have been shown to be monophyletic. A summary of the cladograms for the Cactoideae presented in a 2011 paper is shown below (ICSG tribes in bold). Blossfeldia Cacteae Calymmantheae (i.e. Calymmanthium ), species of Copiapoa and Frailea including members of Pachycereeae , Hylocereeae and Browningieae Rhipsalideae other core Cactoideae II, including members of Notocacteae , Trichocereeae , Cereeae and Browningieae The classification of
80-453: A thick cortex , an extensive system of cortical bundles, collapsible cortical cells, and medullary bundles. Typically, the epidermis consists of a single layer of irregularly shaped cells, a cuticle at least 1-2 microns thick, and long, uniseriate trichomes 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;
100-599: The Cactaceae thus remains subject to change, from the genus level upwards. In 2016, David Hunt wrote that "the advent of molecular systematic studies in the past two decades will hopefully have a stabilizing effect on classification in due course, but has so far had the opposite effect". In 2010, Nyffler and Eggli produced a classification based on an explicit phylogeny. The broad outlines of their cladogram agree with that of Hern et al. (2011), shown above, although some details are different. Their classification corresponds to
120-452: The ICSG classification of the subfamily Cactoideae (as presented by Anderson in 2001 ) with a 2002 classification of the subfamily Opuntioideae. There are differences in the genera recognized in the systems; where the older system does not recognize the genus, "–" is shown. Unless otherwise indicated, the subfamily placement of the genera listed here is based on Anderson's 2001 presentation of
140-590: The ICSG classification, as is the tribal placement of the genera of the subfamily Cactoideae. The division of the subfamily Opuntioideae into tribes is additional to the ICSG system. International Organization for Succulent Plant Study The International Organization for Succulent Plant Study (IOS) describes itself as a "non-governmental organization promoting the study and conservation of succulent and allied plants and encouraging collaboration among scientists and curators of significant living collections of such plants, professional or amateur." In 1984, it
160-420: The basis of many published classifications. Detailed treatments produced in the 21st century have divided the family into around 125–130 genera and 1,400–1,500 species, which are then arranged into a number of tribes and subfamilies. The ICSG classification of the family recognizes four subfamilies: Pereskioideae (consisting only of the genus Pereskia ), Opuntioideae , Maihuenioideae (consisting only of
180-478: The cladogram shown below. Pereskia A Pereskia B Maihuenia incertae sedis Cylindropuntieae Opuntieae Blossfeldia ( Blossfeldieae ) Cacteae incertae sedis Phyllocacteae Rhipsalideae Notocacteae Cereeae The table below shows how the genera recognized by Nyffler and Eggli are placed into their subfamilies and tribes (they also use some subtribes, not shown here). The column headed "Older tribe (if different)" shows
200-413: The first plant conservation organization with a strict code of conduct for all members to follow, detailing principles to conduct field research, specimen collection, maintenance and management of field collected materials. The IOS is run by a board of 6 executive members, these positions are elected by organization members for 2 year long terms. Executive positions include a President, a Vice-President,
220-579: The genera within the Opuntioideae are not monophyletic. Maihueniopsis is highly polyphyletic , appearing in four separate lineages. The two largest genera within the subfamily, Opuntia and Cylindropuntia are also not monophyletic. The classification of the Opuntioideae is thus uncertain as of March 2012 ; Griffith and Porter say that changes in classification will require "broad information (of multiple data types) regarding all species of opuntioid cacti". The ICSG classification divides
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#1732790922197240-504: The genus Maihuenia ) and Cactoideae . Molecular phylogenetic studies suggest that Pereskia is not monophyletic (i.e. its species are not the complete set of descendants of a common ancestor), so that Pereskioideae is not monophyletic although the three other subfamilies are. The Bayesian consensus cladogram from a 2005 study is shown below: Pereskia Clade A Pereskia Clade B Opuntioideae Maihuenioideae Cactoideae Five tribes have been recognized within
260-701: The reason for this is unknown. They also possess mucilage cells. Notably, their lack of collapsible cortical cells, ribs, and tubercles 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 bundles, which in other cacti protect against sucking insects and stiffen developing internodes . Tribes and genera of
280-413: The same systematic results. Specifically, there was differences in yielded relationships based on what genetic sequences and analysis was being utilized. In 2010, it was proposed by Nyffeler and Eggli, as part of a larger overhaul of Cactaceae systematics, to only recognize Cylindropuntieae and Opuntieae as true tribes of Opuntioideae, since they are the tribes generally agreed upon to be monophyletic. It
300-468: The species level. In addition, the genera within each tribe exhibits variation in morphology , which makes using genetic analysis more important in determining relationships, since defining physical characteristics may be unseen in some genera. In 2009, a study by Griffith and Porter, based on ribosomal intergenic spacer analysis defined four tribes of Opuntioideae: However, this classification has been questioned by additional research that did not yield
320-428: The subfamily Cactoideae into nine tribes. However, phylogenetic research has not supported most of these tribes, nor even the genera of which they are composed. A 2011 study found that "an extraordinarily high proportion of genera" were not monophyletic, including 22 (61%) of the 36 genera in the subfamily Cactoideae sampled in the research. Of the nine tribes recognized within Cactoideae, one, Calymmantheae , comprises
340-1106: The subfamily Opuntioideae : Tephrocacteae , Pterocacteae , Austrocylindropuntieae , Cylindropuntieae and Opuntieae . All but the first, Tephrocacteae , were shown to be "essentially monophyletic" in molecular phylogenetic study in 2009. A summary of the consensus Bayesian tree is shown below (tribes are bold; the number of species in the study is shown in parentheses). Puna (1), Maihueniopsis (3), Cumulopuntia (1) = Tephrocacteae (part) Pterocactus (6) = Pterocacteae Maihueniopsis (1), Puna (1), Tephrocactus (7) = Tephrocacteae (part) Maihueniopsis (1), Cumulopuntia (5), Puna (1), Austrocylindropuntia (4) ≈ Austrocylindropuntieae Quiabentia (1), Pereskiopsis (2), Micropuntia (2), Cylindropuntia (12), Grusonia s.s. (1), Corynopuntia (6) ≈ Cylindropuntieae Miqueliopuntia (1), Tunilla (2), Maihueniopsis (1) Opuntia (2) Brasiliopuntia (1), Opuntia (1), Tacinga (2) Opuntia (28), Consolea (6), Nopalea (7) Many of
360-549: The subfamily Opuntioideae include: Cylindropuntieae – round stems Opuntieae – flattened stems Tephrocacteae – round stems Current research shows conflicting arguments over the phylogenetic accuracy of the tribes and genera listed above. A major challenge in Opuntioideae classification is that the subfamily is known to hybridize (particularly the Opuntieae tribe), which further complicates how to define at
380-691: Was decided that the Cactaceae Section of the IOS should set up a working party, now called the International Cactaceae Systematics Group (ICSG), to produce consensus classifications of cacti down to the level of genera . Their system has been used as the basis of subsequent classifications. The IOS focuses on global research and conservation of the succulent plant families (Agavaceae, Aloaceae, Cactaceae, Crassulaceae, Portulacaceae, Talinaceae). It later became
400-528: Was proposed to include all other genera into one polyphyletic basal group until further research concludes more definitive answers to their phylogeny. Cylindropuntieae The classification of the family Cactaceae remains uncertain as of August 2023 . Since the mid-1990s, the system produced by the International Cactaceae Systematics Group (ICSG) of the International Organization for Succulent Plant Study has been used as
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