Scientific taxonomy article
Accepted name and publication history
The accepted name in the current Kew backbone is Gymnocalycium horstii Buining. Buining published the species in 1970 in Kakteen und andere Sukkulenten 21: 162. IPNI supplies nomenclatural authorship and place of publication, while current acceptance, synonymy, and native distribution follow POWO's taxonomic opinion.12
The name was published directly in Gymnocalycium, not as a new combination, so there is no separate basionym author in parentheses.
Taxon boundary and infraspecific treatment
In the Kaktüs Doktoru backbone, the species is a child of the genus Gymnocalycium. Kew recognizes two accepted subspecies: subsp. horstii and subsp. buenekeri. This package updates only the canonical species node and its linked botanical-dictionary record; it does not collapse accepted subspecies into species synonyms, rewrite the genus node, or alter the product.
Diagnostic characters
A depressed-globose stem, pronounced continuous ribs, sparse bristly spines, and white, cream, or pink flowers are assessed together in identification. These characters must be assessed together. A single commercial photograph is not an herbarium voucher, and colour, spine length, or stem form may shift with cultivation conditions.
Phylogenetic context
A broad plastid-DNA study recovered Gymnocalycium as monophyletic but found that several older morphology-only infrageneric groups were not natural: Microsemineum was polyphyletic and Macrosemineum paraphyletic. The study recommends reading seed morphology together with molecular evidence.3 This does not by itself change the accepted name of this species; it warns against inferring close relationship from one conspicuous surface character.
Native distribution and conservation
Kew records the native range as Rio Grande do Sul, Brazil.1 WFO describes a rupicolous succulent with a depressed stem and pale-to-dark green epidermis; its narrow southern-Brazilian range increases sensitivity to habitat loss. The stored conservation category is EN.4 The IUCN record assesses the species as Endangered, so the previous live LC field will not be retained. Subspecies names and commercial inventory must not be confused with this global assessment.
Synonymy and retrieval
Kew lists no direct species-level synonym. Kew recognizes two accepted subspecies: subsp. horstii and subsp. buenekeri. Flattening accepted subspecies into species synonyms would mix taxonomic ranks.1
References
- Plants of the World Online. “Gymnocalycium horstii Buining.” Royal Botanic Gardens, Kew. Accessed: 2026-08-04. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:115397-2 ↩
- International Plant Names Index. “Gymnocalycium horstii Buining.” Accessed: 2026-08-04. https://www.ipni.org/n/115397-2 ↩
- Demaio, P. H. et al. “Molecular phylogeny of Gymnocalycium (Cactaceae).” American Journal of Botany 98(11): 1841–1854. https://doi.org/10.3732/ajb.1100054 ↩
- IUCN Red List of Threatened Species. “Gymnocalycium horstii.” https://www.iucnredlist.org/species/152340/625698 ↩
- World Flora Online. “Gymnocalycium horstii Buining.” Accessed: 2026-08-04. https://www.worldfloraonline.org/taxon/wfo-0000712488 ↩
