Maihueniopsis is a genus of low-growing, spiny cacti in the family Cactaceae (order Caryophyllales), placed within the subfamily Opuntioideae and tribe Tephrocacteae. The genus was described by the Argentine botanist Carlo Luigi Spegazzini in 1925 and currently comprises around 18 accepted species, though taxonomic counts vary between sources.
Plants in this genus form compact, cushion-like or mat-forming clumps of small, segmented stems with pronounced spines, characteristic of the Tephrocactus alliance within the opuntioid cacti. They are native to the Andean and Patagonian regions of South America, primarily in Argentina and Chile, where they grow at high elevations in arid and semi-arid habitats.
The genus has a complex nomenclatural history. Several former segregate genera — including Puna R.Kiesling and various Opuntia series — have been reduced to synonymy under Maihueniopsis. The name itself refers to the genus's superficial resemblance to the unrelated genus Maihuenia, combined with the Greek suffix -opsis ("resemblance" or "appearance").
Notable members include Maihueniopsis darwinii, named after Charles Darwin who collected specimens during his Beagle voyage, M. glomerata, M. ovata, and M. clavarioides, which was formerly the type species of the now-synonymised genus Puna.
Etymology
The name Maihueniopsis combines the genus name Maihuenia — another South American cactus genus — with the Greek suffix -opsis, meaning "resemblance" or "appearance". The name was chosen to reflect the superficial visual similarity between the two groups, despite them being unrelated within the family Cactaceae.
Distribution
Maihueniopsis species are native to the Andean and Patagonian regions of South America, with the centre of diversity in Argentina and Chile. Species occur across a range of elevations in arid, high-altitude habitats characteristic of the southern Andes, including the Atacama Desert region and Patagonian steppe. M. darwinii was collected near the Strait of Magellan during Darwin's Beagle voyage, indicating a southern range extending into cold-temperate Patagonia.
Taxonomy Notes
Maihueniopsis was described by Carlo Luigi Spegazzini in 1925 (Anales de la Sociedad Científica Argentina 99: 86) and belongs to subfamily Opuntioideae, tribe Tephrocacteae within Cactaceae. The type species is M. molfinoi Speg. Several genera have been subsumed into Maihueniopsis over time, including Puna R.Kiesling (1982) and Pseudotephrocactus Frič & Schelle (1933). A homotypic synonym, Tephrocactus subg. Maihueniopsis (Speg.) G.D.Rowley, was created when the group was treated as a subgenus of Tephrocactus. The spelling variant Maihuenopsis (omitting one 'i') appears in some literature but is not the accepted form per IPNI.
