in cactusinhabitat.org 2013, the A&M 705, A&M 733, A&M 737, and A&M 744, now identified with E. oxygona, were attributed to Echinopsis rhodotricha K. Schumann
June 2021

In January 2014 we were in the Nuevo Berlin area, in the Department of Rio Negro, Uruguay, searching for populations of Parodia turecekiana R. Kiesling, in relation to the study work on the relationships between this taxon and the other populations composing the Parodia mammulosa complex (Lamaire) N. P. Taylor (Anceschi & Magli 2014, 13: 60-73; 2018, 36: 116-117). In the areas of wooded savanna with allomorphic soil, near the Rio Uruguay, known as "blanqueales", among the forests mainly consisting of "algarrobos", "quebrachos" and the palm "Caranday" (for more informations on the physicochemical composition and the phytogeographic components of the "blanqueales" see Anceschi & Magli 2014, 13: 62), we encountered different populations of Echinopsis oxygona (Link & Otto) Pfeiffer (A&M 967, A&M 972). Again, as on other previous occasions we have faced the perplexing situation of having to see that within the same population there were present semaphoronts (Hennig 1966, 6-7, 32-33, 63, 65-67), attributable to E. oxygona (see A&M 967, photos 77-85, 87-89), and others more attributable to Echinopsis rhodotricha K. Schumann, (always see A&M 967, photo 86). And again, see A&M 972 (photos 92-95) for individuals closest to the first taxon, and in the same population of A&M 972 (photos 90-91), for those closest to the characters of the second. Considering that also in other populations found within the "blanqueales" of the Rio Uruguay, we had observed an overlap of the elements that should characterize the two taxa (see below). An example is the population of Young, Rio Negro, Uruguay, A&M 277 (photos 11-17), which shows intermediate characters (in habit and spination), and we had thought that the two species could cross just in the "blanqueales" which, as already highlighted (Marchesi 2013, quoted from Anceschi & Magli 2014, 13: 62), represents an extension of the Humid Chaco ecoregion. We know that E. rhodotricha (including Echinopsis chacoana Schütz, see Anceschi & Magli 2013a, 50), is recognized as an endemic dominant species of the Chaco, while E. oxygona in turn lives on a large extension of territory, in habitats mostly consisting of Pampa grasslands with rocky outcrops in Argentina, Uruguay and Southern Brazil, in the Humid and Semi-arid Pampas of Argentina, Uruguay and Southern Brazil Ecological region, but also detectable in the "blanqueales", part of the Paranà flooded savanna Ecological region. In fact it is known that the two taxa are sympatric in this area (data gathered from: Larocca, J., Machado, M., Kiesling, R., Oakley, L. & Pin, A. 2017. Echinopsis oxygona [geographic range], (amended version of 2013 assessment). The IUCN Red List of Threatened Species 2017. Downloaded on 07 December 2019) & Oakley, L., Duarte, W. & Pin, A. 2017. Echinopsis rhodotricha [geographic range], (amended version of 2013 assessment). The IUCN Red List of Threatened Species 2017. Downloaded on 05 December 2019). But re-evaluating all the populations of these two dominant species that we visited on many occasions in the vastness of their distribution areas, we realized that the overlapping of the distinctive semaphoronts wasn't related only to the "blanqueales", where it is known that the two species overlap, but also in other "not suspected" areas, far from the recognized areas of sympatry. See for example the populations of E. rhodotricha, which we detected in 2011 in Bolivia, Santa Cruz, Santiago de Chiquitos, Valle de Tucavaca, in the northernmost distribution area of the taxon, very far from what is recognized to be the distribution range of E. oxygona, where many individuals show the traits belonging to the second taxon (A&M 705, photos 04, 07, 14-15, 22). On the other hand, consider that it is not difficult to encounter what should be the distinctive characters of E. rhodotricha, in the pampas of southern Brazil, in the state of Rio Grande do Sul, or in the north of Uruguay, areas which should be the prerogative of E. oxygona. In this regard, see our A&M 86 (photo 03), A&M 260 (photo 08); A&M 283 (photo 18), A&M 286 (photo 23), A&M 767 (photo 26), A&M 777 (photos 30-31). However, if within the same natural population, two distinct semaphoronts are elected, indicating distinct phases in the ontogenesis process of the taxon, as representative instead of two distinct taxa, it will give rise to the creation of non-existent species. This is what happens for example on the IUCN website (ibidem, see Pierre Braun's photos), where for E. oxygona a semaphoront representing a globular plant is chosen, with evident felted and protruding areolas, without or with small inconspicuous spines; and for E. rhodotricha a more elongated semaphoront, with a strong spination. More or less the same selection of images was done by Hunt et al. (2006, atlas: 243-244). As already highlighted, it is demonstrable that the two taxa in the "distinct areas of election" show both semaphoronts. Based on what has been revealed, we have assimilated E. rhodotricha into the synonymy of E. oxygona in cactusinhabitat.org. Thus E. oxygona assumes the range of an even wider dominant species, which from the Tucavaca Valley, Santa Cruz, Bolivia, located at the extreme north of the taxon’s distribution, populating the Dry Chaco, the Humid Chaco, the Humid and Semi-arid Pampas of Argentina, Uruguay and Southern Brazil, and the Paranà flooded savanna ecological regions, reaches to the south the areas west of the city of Buenos Aires. (Quoted from Anceschi & Magli 2021, 61-63)