During our 2015-2016 study tour, we spent the months of June and July making surveys in the states of Minas Gerais and Bahia, Brazil. One of the species of interest was the dominant Cereus jamacaru De Candolle, a taxon which is distributed in 7 Brazilian states (i.e. Alagoas, Bahia, Goiás, Maranhão, Minas Gerais, Pernambuco, Sergipe), at heights between 50 and 1200 m asl. (data gathered from: Braun, P., Machado, M. & Taylor, N. P. 2017. Cereus jamacaru (amended version of 2013 assessment). The IUCN Red List of Threatened Species 2017. Downloaded on 11 January 2020). Travelling in a north-eastern direction through the Caatinga ecoregion, a part of the Tropical & Subtropical Dry Broadleaf Forest Biome (Olson, D. M. et al. 2001), we came across various populations of the taxon in an area between Montes Claros (north Minas Gerais) in the south (A&M 1381), and Ituaçu (central-south Bahia), in the north (A&M 1440). Regarding the taxonomic understanding of this species, Hunt et al. (2006, text: 40), divided the taxon into two ssp., recognizing in addition to ssp. jamacaru, the ssp. calcirupicola;  having  young plants (c.10-100 cm in high) of the first taxon with only 3-7 ribs versus  5-8 ribs present in the second, on specimens of the same height. Our surveys show that, if it is true that young specimens of calcirupicola populations, in the above-mentioned height range, they can show 4-8 ribs at the base versus an average of 7 in the jamacaru populations; it must be considered that in the upper part of the stem (i.e. c. 100 cm in high), in both taxa the rib count becomes 4-5. See A&M 1381 (calcirupicola populations), photos 11-16; A&M 1385 (calcirupicola populations), photos 21-24 and A&M 1395 (jamacaru populations), photos 39-40; in addition to A&M 1396 (jamacaru populations), photos 48-49. We find it difficult to distinguish taxa solely on the basis of these differences, within dominant species of such a geographical extent. The only discernible difference within the species is constituted by the fact that, while jamacaru populations tend to grow in the flatter part of the Caatinga, the plant we call calcirupicola has populations growing on the rocky outcrops of this ecoregion. We would like to recall that occupying distinct habitats is part of the normal expansion process of a dominant species in the Darwinian evolutionary sense (Darwin, 1859), with the slight morphological variations that this entails. In this sense we consider Cereus calcirupicola (F. Ritter) Rizzini and Cereus jamacaru ssp. calcirupicola (F. Ritter) N. P. Taylor & Zappi synonymous with C. jamacaru. Anderson & Eggli (2011, 107-108), distinguish within C. jamacaru, also Cereus jamacaru ssp. goiasensis (F. Ritter) P. J. Braun & Esteves, always for a labile distinction based on the number of ribs (i.e. 5-7, at the base of the young plants (<100 cm in height). But based on Taylor & Zappi (2018, 36: 9), who consider the last taxon (as Piptanthocereus goiasensis) synonymous with Cereus hexagonus (Linné) Miller, we prefer to exclude C. jamacaru ssp. goiasensis from the synonymy of C. jamacaru. (Quoted from Anceschi & Magli 2021, 44-45)
July 2021