Opuntioideae

Opuntioideae
Cylindropuntia ramosissima
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Caryophyllales
Family: Cactaceae
Subfamily: Opuntioideae
Burnett
Tribes[1][2]
  • Cylindropuntieae
  • Opuntieae
  • 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.[3] 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.[4]

Description

Synapomorphies of Opuntioideae include small deciduous, barbed spines called glochids born on areoles and a bony aril surrounding a campylotropous ovule (inverted and curved, such that the micropyle almost meets the funiculus).[5] 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 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; 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.[6]

Taxonomy

See also: Taxonomy of the Cactaceae

A major challenge in Opuntioideae classification is that the subfamily is known to hybridize (particularly the Opuntieae tribe), which complicates identifying species.[7] Genera exhibit variation in morphology, which makes using genetic analysis more important in determining relationships, since physical characteristics used to define genera may be unseen in some of them.[8]

In 2009, a study by Griffith and Porter, based on ribosomal intergenic spacer analysis defined four clades within the Opuntioideae:[5]

  1. Core Maihueniopsis - which was shown as monophyletic through genetic analysis
  2. Pterocactus - defined by a winged seed
  3. Terete-stemmed - defined by cylinder-shaped stems
  4. Flat-stemmed - defined by flat stems

They noted that the boundaries of some genera as then circumscribed were unclear.[5]

Later research found different relationships based on what genetic sequences and analysis was used.[4][9] 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 basal group until further research produced more definitive answers to their phylogeny.[10]

A 2020 study using chloroplast genome sequences found a much clearer division into three monophyletic tribes. Their maximum likelihood cladogram is shown below (the genus Punotia was not included in the study).[1]

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.[1]

Tribes and genera

The tribes and genera of the subfamily Opuntioideae as of January 2025 are:[1][11]

Austrocylindropuntia subulata

Cylindropuntieae – round stems

Cylindropuntia bigelovii

Opuntieae – flattened stems

Tephrocacteae – round stems

Intergeneric hybrids

  • × Opulea M.H.J.van der Meer (Consolea × Opuntia)

See also

References

  1. ^ a b c d Köhler, Matias; Reginato, Marcelo; Teixeira Souza-Chies, Tatiana & Majure, Lucas C (2020). "Insights Into Chloroplast Genome Evolution Across Opuntioideae (Cactaceae) Reveals Robust Yet Sometimes Conflicting Phylogenetic Topologies". Frontiers in Plant Science. 11: 729. doi:10.3389/fpls.2020.00729. PMC 7317007. PMID 32636853.
  2. ^ "Family: Cactaceae Juss., nom. cons. subfam. Opuntioideae". Germplasm Resources Information Network. United States Department of Agriculture. 2004-02-13. Archived from the original on 2012-08-25. Retrieved 2011-12-05.
  3. ^ Anderson, Edward F. (2001). The Cactus Family. Portland, OR: Timber Press. ISBN 0881924989.
  4. ^ a b Ritz, C.M.; Reiker, J.; Charles, G.; Hoxey, P.; Hunt, D.; Lowry, M.; Stuppy, W.; Taylor, N. (2012). "Molecular phylogeny and character evolution in terete-stemmed Andean opuntias (Cactaceae−Opuntioideae)". Molecular Phylogenetics and Evolution. 65 (2): 668–681. Bibcode:2012MolPE..65..668R. doi:10.1016/j.ympev.2012.07.027. PMID 22877645.
  5. ^ a b c Griffith, M. Patrick; Porter, J. Mark (2009-01-01). "Phylogeny of Opuntioideae (Cactaceae)". International Journal of Plant Sciences. 170 (1): 107–116. doi:10.1086/593048. ISSN 1058-5893.
  6. ^ Mauseth, James D. (2005-12-01). "Anatomical features, other than wood, in subfamily opuntioideae (cactaceae)". Haseltonia. 11: 113–125. doi:10.2985/1070-0048(2005)11[113:afotwi]2.0.co;2. ISSN 1070-0048.
  7. ^ Majure, Lucas; Judd, Walter; Soltis, Pam; Soltis, Doug (2012-02-14). "Cytogeography of the Humifusa clade of Opuntia s.s. Mill. 1754 (Cactaceae, Opuntioideae, Opuntieae): correlations with pleistocene refugia and morphological traits in a polyploid complex". Comparative Cytogenetics. 6 (1): 53–77. doi:10.3897/compcytogen.v6i1.2523. ISSN 1993-078X. PMC 3833768. PMID 24260652.
  8. ^ Bárcenas, Rolando T. (August 2016). "A molecular phylogenetic approach to the systematics of Cylindropuntieae (Opuntioideae, Cactaceae)". Cladistics. 32 (4): 351–359. doi:10.1111/cla.12135. PMID 34740297.
  9. ^ Hernandez-Hernandez, T.; Hernandez, H. M.; De-Nova, J. A.; Puente, R.; Eguiarte, L. E.; Magallon, S. (2010-12-23). "Phylogenetic relationships and evolution of growth form in Cactaceae (Caryophyllales, Eudicotyledoneae)". American Journal of Botany. 98 (1): 44–61. doi:10.3732/ajb.1000129. ISSN 0002-9122. PMID 21613084.
  10. ^ Nyffeler, Retro, Eggli, Urs (2010). "A Farewell to Dated Ideas and Concepts: Molecular Phylogenetics and a Revised Suprageneric Classification of the family Cactaceae" (PDF). Schumannia. 6: 109–149 – via uzh.ch.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. ^ "GRIN Genera of Cactaceae subfam. Opuntioideae". Germplasm Resources Information Network. United States Department of Agriculture. Archived from the original on 2015-09-24. Retrieved 2011-12-05.