Studies in habitat between 2006 and 2011 convinced us that, contrary to the conclusions of the recent literature (Hunt et al.,  2006, text: : 129; Charles 2009, 42-43), Gymnocalycium buenekeri Swales is not related to Gymnocalycium horstii Buining, and that, instead, the latter taxon is more closely related to Gymnocalycium denudatum (Link & Otto) Pfeiffer ex Mittler. There are two reasons: the first, and most important, is that in the populations of G. buenekeri studied in the area of São Francisco de Assis, the homeland of the taxon, all the individuals have a dull epidermis (A&M 781, photos 01-18, A&M 783, photos 19-45, A&M 785, photos 46-67). On the other hand, in the populations of G. horstii, in the area of Minas de Camaquã and Santana da Boavista, all individuals show a glossy epidermis (A&M 797, photos 1-32), a character reminiscent of G. denudatum (A&M 84, photos 01-08, A&M 263, photos 09-17, A&M 788, 18-20 photos, A&M 801, photos 21-27), with whom they sometimes share their habitat (Gerloff 1999). As in the case of Gymnocalycium stenopleurum F. Ritter and Gymnocalycium mihanovichii (Fric ex Gurke) Britton & Rose, where the two taxa, although morphologically very similar to each other, are distinguished by the diversity of the epidermis, rough in the first vs. smooth in the second, also in this case we believe that the distinctive characters shown in all the individuals of the two species, indicate that they come from distinct lineages. The second reason is that the distance between the distribution area of G. buenekeri and that of G. horstii is 200 km as the crow flies, where intermediate populations have not been detected. In the corresponding case mentioned, on the other hand, there are areas where G. stenopleurum and G. mihanovichii overlap, and where the two species live side by side (Charles 2009, 258-259, 258, fig 604), but despite this, based on the character of the different epidermis, they are defined as separate species. We are therefore faced with the same type of evidence, strengthened by the disjunction of the range. For these reasons we consider the taxon G. buenekeri from São Francisco de Assis distinct from G. horstii. (Quoted from: Anceschi & Magli 2013b, 64-65)

We thank the Prefeitura of São Francisco de Assis for their help and for their commitment to safeguarding the taxon. (June 2013)

Specimens of considerable size:

group 46 x 63 cm, greater stem 13 x 14 cm (h x ø) (photos 46-56). (June 2013)