Autor: (Berger) Britton & Rose
• ETYMOLOGY
“Thick Cereus “, referring to the massive size of the columnar stems in this genus.
• DESCRIPTION
A genus of treelike, massive columnar plants, often strongly branched (P. weberi), ribs 7-17, sometimes bearing a pseudocephalium. Areoles rounded to elliptic, felted, usually connected by a interareolar groove in the reproductive area, with flexible spines. Radial spines barely differentiated from the centrals, which are usually longer and sturdier.
Flowers usually nocturnal, but remaining open the following day, self-sterile or self-fertile (P. grandis, pers. obs. 2014), bell-shaped to funnel-shaped, whitish or pink, bearing scales, trichomes and spines, pollinated by bats (Antrozous pallidus, Artibeus intermedius, A.jamaicensis, Chiroderma salvini, Choeroniscus godmani, Choeronycteris mexicana, Glossophaga soricina, Leptonycteris curasoae, L. nivalis, L. yerbabuenae, Sturnira lilium), also by hummingbirds
(Calypte costae, Cynanthus latirostris, Selasphorus rufus), other birds (Auriparus flaviceps, Carpodacus mexicanus, Colaptes auratus, Melanerpes uropygialis, Psaltriparus minimus, Toxostoma curvirostre, Zenaida asiatica, Z. macroura), as well as bees (Apis mellifera, Trigona sp.) and Sphingideae (Hyles lineata). Fruits mostly spiny, globose with fleshy white, yellow or magenta funicles, with apical or longitudinal dehiscence. Seeds more or less egg-shaped, very big and numerous (up to 800 per fruit), brownish to black, shiny, finely tuberculate and striate, ornithophilous dispersal.
• HABITAT
The genus Pachycereus has a wide area of distribution, from northern to southern Mexico, also on islands of the Gulf of California, and grows endemically, forming widespread colonies dominating the landscape, among shrubs and bushes, in areas of coastal plains, in different types of forests, sandy or rocky soils, in alluvial areas, from sea level (P. pringiei), up to 1800 m in altitude (P. weberi), often together with other cacti and succulents.
• DISTRIBUTION
Mexico (Baja California, Chihuahua, Colima, Durango, Guerrero, Jalisco, Mexico, Michoacan, Morelos, Nayarit, Puebla, Oaxaca, Sinaloa, Sonora, Zacatecas).
Currently 5 recognized species:
– Pachycereus grandis* Rose 1909
– Pachycereus pecten-aboriginum* (Engelm.) Britton & Rose 1909
– Pachycereus pringiei* (S.Watson) Britton & Rose 1909
– Pachycereus tepamo* S.Gama & S.Arias 1998
– Pachycereus weberi* (J.M.Coult.) Backeb. 1960
References: "TAXONOMY of the CACTACEAE" - ISBN 978-84-617-3692-8 (Vol. 2)