Pachycereus
Pachycereus in Contr. U.S. Natl. Herb. 12: 420. 1909 sec. Franco-Estrada & al. 2021
- ≡Cereus subg. Pachycereus in Rep. (Annual) Missouri Bot. Gard. 16: 63. 1905 syn. sec. Arias & Terrazas 2009
- Type: Pachycereus pringlei
Notes
Phylogenetic studies based on morphological and molecular data show consistently that Pachycereus s.str. is a monophyletic group with five species (Arias & al. 2003; Arias & Terrazas 2006, 2009; Arias & al. 2012; Franco-Estrada 2021). Other species previously considered in Pachycereus (Buxbaum 1961; Gibson & Horak 1978; Anderson 2001; Hunt 2006; Nyffeler & Eggli 2010) have been transferred to Lemaireocereus, Lophocereus, and Cephalocereus. Pachycereus s.str. includes tree-like species, interareolar grooves on the stems, abundant trichomes on flower, and flexible spines on the fruit.
The phylogenetic position of the two monotypic genera Backebergia and Pterocereus was recently clarified by Franco-Estrada & al. (2021). Pterocereus (P. gaumeri) was resolved as sister to Lophocereus (1 PP) while Backebergia (B. militaris) was resolved as sister to the clade of Marshallocereus + (Pterocereus + Lophocereus), both placements were maximally supported by Bayesian Inference (1 PP), justifying their generic status separate from Pachycereus.A
The phylogenetic position of the two monotypic genera Backebergia and Pterocereus was recently clarified by Franco-Estrada & al. (2021). Pterocereus (P. gaumeri) was resolved as sister to Lophocereus (1 PP) while Backebergia (B. militaris) was resolved as sister to the clade of Marshallocereus + (Pterocereus + Lophocereus), both placements were maximally supported by Bayesian Inference (1 PP), justifying their generic status separate from Pachycereus.A
Taxon standing
Category B. The genus is monophyletic based on phylogenetic studies that support the clade based on a sufficiently dense or even complete sampling, or support a monotypic genus as a distinct lineage, but do not provide a new taxonomic treatment at the species level. In many cases, older classical taxonomic synopses or a monographic treatment exist for these genera providing a reliable assessment of the species included.B