Five species
The genus contains Pachycereus grandis, P. pecten-aboriginum, P. pringlei, P. tepamo and P. weberi. POWO treats Anisocereus and Tribularia as generic synonyms. P. pringlei occurs in northwestern Mexico, whereas P. tepamo is associated with southwestern Mexico and seasonally dry tropical forest. The large columnar habit therefore unites species from contrasting habitats. [2-WWW] [2-WWW] [2-WWW]
Stems and flowering zones
Areoles, the small fields that produce spines and flowers, change their appearance along a stem. In the morphological comparison by Gama-López and Arias, sterile and flowering zones were distinguished in P. tepamo, P. grandis and P. pecten-aboriginum. Such a boundary was not distinguished in P. weberi. Identification therefore requires examination of mature stem portions together with flowers, rather than a young growth tip alone. [Gama-López and Arias 1998]
Reproductive variation
P. pringlei includes populations with different proportions of male, female and hermaphroditic plants, as well as different chromosome numbers. P. pecten-aboriginum has self-incompatible hermaphroditic flowers and geographic variation in flower opening duration and pollinator contributions. These traits describe particular species and populations. The breeding system of one Pachycereus does not automatically define the biology of the others. [Gutiérrez-Flores et al. 2018] [Valiente-Banuet et al. 2004]
Synonyms and names in the literature
Anisocereus · Tribularia [2-WWW]