A name preserves classification history
Moving a species to another genus creates a new name combination based on the same nomenclatural type. This produces homotypic synonyms. Bárcenas and Hawkins traced this phenomenon in grusonias, showing periods of intensive species transfers between Opuntia, Corynopuntia and Grusonia. Name numbers could rise rapidly while the number of recognised species remained similar. [Bárcenas and Hawkins 2017]
A nomenclatural type is the reference point for applying a name. The 2012 treatment of four Engelmann names used preserved stem, fruit and flower fragments, seeds and historical illustrations. Selecting appropriate material stabilises the link between name and description, even when subsequent interpretations of relationships change. [Bárcenas et al. 2012]
Micropuntia separates from Grusonia
Micropuntia pulchella (as Grusonia pulchella in the title of Griffith's paper) stands out through its cushion growth, underground organ traits and the direction of barbs on fruit spines. ITS analysis supported its distinctness. However, successive plastid reconstructions differed in identifying the nearest sister lineage. [Griffith 2002]
In 2016, three plastid markers placed it beside Pereskiopsis. In 2019, plastome analysis indicated a lineage sister to the combined group Grusonia + Cylindropuntia. Together, the results show changes in the relationship hypothesis with data scope and taxon sampling, while maintaining the genus's distinctness. [Bárcenas 2016][Majure et al. 2019]
A genus can contain subgenera
The 2023 proposal organises Grusonia into two subgenera, Corynopuntia and Grusonia, and four sections. The name Corynopuntia in an older paper may therefore refer to a genus, while in a new classification it refers to a unit within Grusonia. In the atlas, the current name accompanies the source name, for example Grusonia halophila (described as Corynopuntia halophila). [Bárcenas 2023][Donati 2018]
A new species and a new rank
In 2025, Donati described Grusonia pulvinata from San Luis Potosí and Zacatecas. According to the abstract, it differs from the similar G. vilis in traits including stronger segment junctions and a greater tendency towards sexual reproduction. The same paper proposed G. grahamii subsp. vilis (formerly G. vilis). Both changes concern taxon boundaries, alongside earlier generic transfers. [Donati 2025]
A hybrid between genera
×Cylindronia robertsii (formerly Grusonia robertsii) comes from Baja California Sur. Combining morphology, plastid DNA and nuclear ribosomal DNA indicated hybridisation between Grusonia invicta and Cylindropuntia alcahes subsp. alcahes. According to the results presented, the grusonia was the maternal parent and the cholla the paternal parent. The hybrid name ×Cylindronia was introduced for this combination of genera. [Baker et al. 2022]
In botanical notation, × signals hybrid origin. The name change organises the identified relationship between lineages, while the name used in the older description is retained in parentheses. Material described as Grusonia robertsii thus remains linked to the later interpretation. [Baker et al. 2022]
Prepared from scientific publications. Names follow POWO. Historical names are given in discussions of older papers.
Nomenclatural proliferation and the superabundance of Homotypic Synonyms in Grusonia (Opuntioideae, Cactaceae)
Bárcenas R. T., Hawkins J. A., Nomenclatural proliferation and the superabundance of Homotypic Synonyms in Grusonia (Opuntioideae, Cactaceae), Haseltonia, 2017, 23:27-34, doi: 10.2985/026.023.0104
The historical compilation of names in the Grusonia group shows how changes in generic placement produced successive homotypic synonyms. The authors distinguish an increase in the number of nomenclatural combinations from a change in the number of recognised species.
Phylogenomics in Cactaceae: A case study using the chollas sensu lato (Cylindropuntieae, Opuntioideae) reveals a common pattern out of the Chihuahuan and Sonoran deserts
Majure L. C., Baker M. A., Cloud-Hughes M., Salywon A., Neubig K. M., Phylogenomics in Cactaceae: A case study using the chollas sensu lato (Cylindropuntieae, Opuntioideae) reveals a common pattern out of the Chihuahuan and Sonoran deserts, American Journal of Botany, 2019, 106(10):1327-1345, doi: 10.1002/ajb2.1364
The plastid genome analysis reconstructs relationships among chollas and other Cylindropuntieae. It includes biogeography, estimates of lineage ages and the evolution of morphological traits. The repeated emergence of similar traits explains some discrepancies between traditional divisions and the molecular tree.
Typification of four North American club-chollas: The names of four Engelmannian species from Mexico and Southwestern United States
Bárcenas R. T., Hawkins J. A., Chiang F., Typification of four North American club-chollas: The names of four Engelmannian species from Mexico and Southwestern United States, Haseltonia, 2012, 17:66-69, doi: 10.2985/1070-0048-17.1.8
Typification of the names Opuntia bulbispina, O. clavata, O. emoryi and O. grahamii, now belonging to Grusonia. The study compares surviving herbarium material, Engelmann's descriptions and historical illustrations, and explains the choice of nomenclatural types.
Grusonia pulchella classification and its impacts on the genus Grusonia: Morphological and molecular evidence
Griffith M. P., Grusonia pulchella classification and its impacts on the genus Grusonia: Morphological and molecular evidence, Haseltonia, 2002, 9:86-93
Morphological and molecular evidence for the distinctness of Micropuntia pulchella, discussed in the title as Grusonia pulchella. The study compares growth form, the underground organ, fruit spines and nuclear ITS sequences, and presents a new name combination.
A molecular phylogenetic approach to the systematics of Cylindropuntieae (Opuntioideae, Cactaceae)
Bárcenas R. T., A molecular phylogenetic approach to the systematics of Cylindropuntieae (Opuntioideae, Cactaceae), Cladistics, 2016, 32(4):351-359, doi: 10.1111/cla.12135
The analysis of three plastid regions clarifies generic boundaries in Cylindropuntieae. It discusses the removal of Micropuntia pulchella from Grusonia and four lineages within Cylindropuntia. The position of Micropuntia can be compared with the later plastome analysis by Majure and co-authors.
A phylogenetic classification of Grusonia, Opuntioideae, Cactaceae
Bárcenas R. T., A phylogenetic classification of Grusonia, Opuntioideae, Cactaceae, Haseltonia, 2023, 30(1):2-5, doi: 10.2985/026.030.0101
A proposed Grusonia classification based on a phylogeny of five plastid markers. It distinguishes two subgenera and four sections, linking the naming of these units to the phylogenetic lineages identified.
Corynopuntia halophila (Cactaceae), a new species from Coahuila, Mexico
Donati D., Corynopuntia halophila (Cactaceae), a new species from Coahuila, Mexico, Plant Biosystems, 2018, 152(3):386-397, doi: 10.1080/11263504.2017.1297332
The original description of Grusonia halophila under the name Corynopuntia halophila. It covers saline habitats, two types of stem segment, morphometry, vegetative reproduction and a comparison of the tetraploid species with diploid Grusonia moelleri.
Grusonia pulvinata, a new sibling species within G. vilis s.l. (Opuntioideae: Cactaceae)
Donati D., Grusonia pulvinata, a new sibling species within G. vilis s.l. (Opuntioideae: Cactaceae), Phytotaxa, 2025, 712(2):87-106, doi: 10.11646/phytotaxa.712.2.1
A description of Grusonia pulvinata from the alluvial plains of San Luis Potosí and Zacatecas, and the new combination Grusonia grahamii subsp. vilis. The abstract identifies differences in segment joints, reproduction, ecology and karyology.
×Cylindronia, a New Nothogenus Representing the First Reported Hybrid Between Grusonia and Cylindropuntia (Cactaceae)
Baker M. A., Majure L. C., Cloud-Hughes M. A., Rebman J. P., ×Cylindronia, a New Nothogenus Representing the First Reported Hybrid Between Grusonia and Cylindropuntia (Cactaceae), Haseltonia, 2022, 29(1):5-15, doi: 10.2985/026.029.0102
The analysis of morphology, plastid DNA and nuclear ribosomal DNA confirms the hybrid origin of ×Cylindronia robertsii, formerly Grusonia robertsii. It identifies Grusonia invicta as the maternal parent and Cylindropuntia alcahes subsp. alcahes as the paternal parent.
