Genus boundaries and former names
In the treatment adopted, Grusonia includes G. bradtiana and the cactus lineage known in many publications as Corynopuntia. Micropuntia pulchella (formerly also Grusonia pulchella) belongs to a separate genus. This separation is based on molecular data considered together with stem, underground-organ and fruit-spine traits. [Bárcenas 2016] [Griffith 2002] [Majure et al. 2019]
Bárcenas's 2023 classification distinguishes subgenera Corynopuntia and Grusonia and sections Radicaulenta, Xylocaulis, Grusonia and Spinicarpa. In the literature, Corynopuntia may therefore mean a genus or a unit within a genus, depending on the author's system. [Bárcenas 2023]
Structure associated with regeneration
Segments are cylindrical to club-shaped, with tubercles, areoles and glochids. Diagnostic descriptions consider spine shape, flattening or angularity, expansion of the base and surface structure. In G. deinacantha, a strong storage root accompanies loose branching. In G. halophila, the root system is fibrous, and the compact mat produces shorter dispersal segments. [Bárcenas and Hawkins 2017] [Donati 2017] [Donati 2018]
Propagation through detached segments depends on plant architecture. Strong junctions maintain a perennial framework, while weaker ones allow propagules to separate. Their number, rooting ability and survival at the site are assessed separately. In experiments and observations, these successive stages provide different measures of regeneration success. [Donati 2018] [Bobich 2005]
Deserts and range history
The genus's range includes dry areas of Mexico and the southwestern United States. The 2022 biogeographical study found the greatest richness of included species in the Chihuahuan Desert region. G. invicta is associated with the Baja California Peninsula, and G. bradtiana with Coahuila. Desert boundaries and changes in former geographical connections are part of the explanation of these ranges. [Bárcenas and Hernández 2022]
In the analysis of five plastid markers, the mean estimated crown age of the genus was about 3.7 million years. The result places many divergences in the late Pliocene and Pleistocene. It is an estimate from a specific model, with calibration drawn from earlier studies and uneven support for individual nodes. [Bárcenas and Hernández 2022]
Nowe rozpoznania taksonomiczne
The 2025 description of Grusonia pulvinata concerns plants from alluvial plains of northern San Luis Potosí and adjacent Zacatecas. The abstract notes strong segment junctions and a greater role of sexual reproduction compared with G. vilis, among other traits. The same paper proposed the name G. grahamii subsp. vilis (formerly G. vilis). [Donati 2025]
Repeated transfers of species among Opuntia, Corynopuntia and Grusonia left a rich synonymy. Historical names are useful keys to sources. Typifications of four Engelmann names also show the importance of preserved plant fragments and illustrations for unambiguous application of names. [Bárcenas and Hawkins 2017] [Bárcenas et al. 2012]
Scale insects associated with grusonias
Dactylopius gracilipilus was described from the Chihuahuan Desert in Texas, associated with hosts termed Corynopuntia in the paper (Grusonia in the classification adopted here). The insect diagnosis relies on microscopic traits of the female's setae and pores. This type of description documents a specific scale-insect species and its host-plant association. [Van Dam and May 2012]