Cephalocereus

Cephalocereus

Synonymy

Cephalocereus Pfeiff. in Allg. Gartenzeitung 6: 142. 1838 sec. Tapia, H.J., Bárcenas-Argüello, M.L., Terrazas, T. & al., 2017
  • =Cephalocereus subg. Mitrocereus Backeb. in Blätt. Kakteenf. 1938(6). 1938 syn. sec. Tapia, H.J., Bárcenas-Argüello, M.L., Terrazas, T. & al., 2017
  • Mitrocereus (Backeb.) Backeb. in Cactaceae (Berlin) 1941(2): 77. 1942 syn. sec. Tapia, H.J., Bárcenas-Argüello, M.L., Terrazas, T. & al., 2017
  • =Rooksbya (Backeb.) Backeb., Cactaceae Handb. Kakteen. Pereskioideae Opuntioideae 4: 2165. 1960 syn. sec. Tapia, H.J., Bárcenas-Argüello, M.L., Terrazas, T. & al., 2017

Notes

Phylogenetics: Tapia et al. (2017) have reconstructed the phylogeny of the Cephalocereus group using molecular data from seven plastid DNA regions (petL-psbE, psbA-trnH, rpl16, rpl32-trnL, trnL-F, trnQ-rps16, and ycf1), as well as morphological characters. The Cephalocereus group was recovered as monophyletic with high support values, whereas Neobuxbaumia appeared as paraphyletic. The authors have therefore proposed to unite all species of Neobuxbaumia, Cephalocereus, and Pseudomitrocereus in one single genus, for which Cephalocereus is the oldest name. [Editorial]

Archived Note

Monotypic; P. fulviceps was previously included in Pachycereus or Cephalocereus, later elevated to generic rank as Mitrocereus (Backeberg 1942) and later Pseudomitrocereus (Bravo & Buxbaum, in Buxbaum 1961). Arias & al. (2003) found P. fulviceps to be unrelated to Pachycereus and instead as sister sister to a clade of Cephalocereus and Neobuxbaumia. Therefore, Pseudomitrocereus was reinstated by Arias & al. (2012). Pseudomitrocereus is characterized by having distinct fertile stem parts, flowers completely covered with trichomes, and thick axial tissue (pericarpel and receptacle; Buxbaum 1961). Its inclusion in Pachycereus was supported by non-informative attributes (e.g. growth form), shared by other members of Pachycereinae (or Echinocereinae sensu Nyffeler & Eggli 2010). However, it is part of the clade "Cephalocereus" according to Arias & al. (2003), composed by Cephalocerus, Neobuxbaumia, and Pseudomitrocereus. The species of this clade share the presence of prismatic crystals in epidermis, inner stamens and nectarial chamber, while the fruit is dehiscent and the pulp is white (Arias & Terrazas 2006). Mitrocereus was based on the name Pilocereus chrysomallus Lem. as type species, but this name represents another species included in the synonymy of Pachycereus militaris (Audot) D. R. Hunt. Consequently, Buxbaum and Bravo (Buxbaum 1961) proposed the name Pseudomitrocereus, with P. fulviceps as the nomenclatural type.A Phylogenetic studies so far resolved Neobuxbaumia as closely related to Cephalocereus and Pseudomitrocereus (Arias & al. 2003; Arias & Terrazas 2006; Hernández-Hernández & al. 2011), however, these studies did not specifically focus on Neobuxbaumia and its generic limits are therefore not yet firmly established. Arias & al. (2003) found Neobuxbaumia in a weakly supported polytomy with Cephalocereus and Pachycereus fulviceps (F. A. C. Weber ex Schumann) D. R. Hunt (=Pseudomitrocereus) as sister to both. The two Cephalocereus species were well supported as sister to each other, but could not be separated from Neobuxbaumia in any tree (Arias & al. 2003). Bárcenas & al. (2011) and Hernández-Hernández & al. (2011) found Neobuxbaumia to be polyphyletic but the relevant nodes were weakly supported, therefore a monophyletic Neobuxbaumia is neither confirmed not contradicted by the currently available data.B
A. Hernández-Ledesma, P., Berendsohn, W.G., Borsch, T. & al., A taxonomic backbone for the global synthesis of species diversity in the angiosperm order Caryophyllales in Willdenowia 45(3): 281-383. 2015 (as Pseudomitrocereus Bravo & Buxb.), B. Hernández-Ledesma, P., Berendsohn, W.G., Borsch, T. & al., A taxonomic backbone for the global synthesis of species diversity in the angiosperm order Caryophyllales in Willdenowia 45(3): 281-383. 2015 (as Neobuxbaumia Backeb.)