Charles (2009, 83) in recognizing Gymnocalycium carolinense (Neuhuber) Neuhuber as a good species, then wonders why Neuhuber in 1994 first described G. carolinense as a ssp. of Gymnocalycium andreae (Bödeker) Backeberg, rather than relating it to Gymnocalycium bruchii (Spegazzini) Hosseus as in Hunt et al. (2006, text: 126), where it is considered synonymous with the latter taxon, to which in his view it appears to be more related. In our opinion the answer is simple: it is because the populations of G. carolinense are morphologically more related to G. andreae than to G. bruchii. Moreover, in this group of closely related taxa, which also includes Gymnocalycium calochlorum (Bödeker) Y. Ito, that in the complex geographically extend over an area which includes the Sierra Grande, the Sierra Chica and the Sierra de Comechigones in the Province of Córdoba (AR), and the Sierra de San Luis, in the Province of San Luis (AR), if the current conception of G. bruchii were the one expounded by Papsch in Schütziana (2013 (4) 1: 3-26), there would be no holomorphological continuity solution between G. andreae and G. bruchii, as two of the ssp. elected by this author to form the group of G. bruchii (i.e. Gymnocalycium bruchii ssp. brigittae (Piltz) Papsch (ibidem: 6, figs. 21-23) and Gymnocalycium bruchii ssp. carolinense (Neuhuber) Papsch (ibidem: 6, fig. 19), are morphologically closer to the first taxon (ibidem: 7, figs. 25-27) than to the second (ibidem: 4, figs. 1-9, 5, figs. 10-18). So, wanting to keep a distinction between G. andreae and G. bruchii (a distinction also highlighted at the molecular level by Demaio et al. (2011, 98 (11): 1846, 1848, 1850), i.e. between a taxon (G. andreae), larger (<4.5 cm diameter), with fewer ribs (c. 8) and fewer spines (1-3 centrals and 6 radials), (Hunt et al. 2006, text: 126), against one (G. bruchii), of smaller dimensions (1-2 x 1-2 cm (height x diameter), more ribs (c. 10) and more spines (0-3 centrals, and 12-17 radials), sometimes covering the stem surface (ibedem: 127), G. carolinense and G. bruchii ssp. brigittae must be included among the synonyms of G. andreae in order not to create interference phenomena between the parameters that support the separation between the two taxa. Finally, given the current state of knowledge, albeit morphologically and molecularly close (see Demaio et al. 2011, 98 (11): 1846, 1848, 1850), we prefer to keep G. bruchii and G. calochlorum separate. For the morphological relationships between G. andreae and G. carolinense, see the following comparisons:

A&M 1249, G. andreae, Argentina, Córdoba, Tanti, south-west of Tanti, El Descanso, 1949 m (photo 75), with A&M 929 (2013-12-20 & 2013-12-29), (G. carolinense), Argentina, San Luis, La Carolina, north of La Carolina, (photos 10, 41), and A&M 937 (G. carolinense), Argentina, San Luis, La Carolina (photo 55);

A&M 1248, G. andreae, Argentina, Córdoba, Tanti, south-west of Tanti, Arroyo Aguas Turbias, 1746 m (photo 69), with (G. carolinense), A&M 929 (2013-12-20), Argentina, San Luis, La Carolina, north of La Carolina (photo 10);

A&M 1248, G. andreae, Argentina, Córdoba, Tanti, south-west of Tanti, Arroyo Aguas Turbias, 1746 m (photos 65-66) with (G. carolinense) A&M 936, Argentina, San Luis, Inti Huasi (photos 21, 30);

A&M 1248, G. andreae, Argentina, Córdoba, Tanti, south-west of Tanti, Arroyo Aguas Turbias, 1746 m (photos 68) with (G. carolinense) A&M 936, Argentina, San Luis, Inti Huasi (photo 20);

A&M 1248, G. andreae, Argentina, Córdoba, Tanti, south-west of Tanti, Arroyo Aguas Turbias, 1746 m (photos 70) with (G. carolinense), A&M 929 (2013-12-20), Argentina, San Luis, La Carolina, north of La Carolina (photo 01) and (G. carolinense) A&M 936, Argentina, San Luis, Inti Huasi (photo 35).

In summary, because the characters of G. bruchii can be really distinctive with respect to G. andreae, we must consider G. carolinense and G. bruchii ssp. brigittae to be synonomous with the second taxon. Despite the morphological and molecular closeness (ibidem), we prefer to keep G. calochlorum distinct from G. bruchii. (Quoted from Anceschi & Magli 2021, 65-67)