Stenocereus

Stenocereus
File:Stenocereus pruinosus.jpg
Kingdom	Plantae
Family	Cactaceae
Subfamily	Cactoideae
Tribe	Phyllocacteae
SubTribe	Echinocereinae
Genus	Stenocereus
Species
Notes	Taxonomy follows Joël Lodé (2015) with reference to Gibson & Horak (1978), Terrazas (2000), Arias & Terrazas (2006), Nyffeler & Eggli (2010), and Bàrcenas et al. (2011).

Etymology

The name means "narrow Cereus", referring to the typically narrow ribs.

Description

Stenocereus is a diverse genus of columnar cacti ranging from shrubs to large tree-like forms.

• Habit: Arborescent or shrubby; erect, branching, sometimes forming trunks; occasionally creeping (S. eruca).
• Growth form: Often forming dense thickets (e.g. S. gummosus).
• Stems: Robust; usually strongly branched.
• Ribs: Numerous; often tuberculate.
• Areoles: Woolly.
• Spines: Radial spines spreading; 1–4 central spines, often strong, sometimes flattened.
• Flowers: Usually nocturnal; sometimes remaining open during the day; rarely diurnal.
• Flower shape: Funnel-shaped to bell-shaped; often fragrant.
• Floral structures: Scaly, often spiny pericarpel.
• Pollination: Primarily by bats; also by hummingbirds, birds, bees, and occasionally butterflies.
• Fruits: Globose to ovoid; often fleshy; usually edible; spines deciduous; generally lacking persistent perianth.
• Seeds: Relatively large; obovoid; black; shiny; surface variable (smooth, tuberculate, pitted).
• Seed dispersal: By bats, birds, lizards, and small mammals.

Habitat

Occurs in a wide range of arid and semi-arid environments:

• deserts and sandy plains
• rocky slopes and canyons
• volcanic substrates
• xerophytic scrub (matorral)
• coastal regions

Altitude range: from sea level up to ~2120 m.

Distribution

Americas:

• Mexico (widespread)
• United States (Arizona, California)
• Central America (Guatemala)
• Caribbean (Cuba, Puerto Rico, Dominican Republic)
• South America (Colombia, Venezuela)

Taxonomy

A complex and partially unresolved genus.

Key points:

• Includes taxa formerly placed in Rathbunia, Hertrichocereus, Machaerocereus, Lemaireocereus, and others
• Morphological characters (silica bodies, pigments, triterpenoids) helped define the group (Gibson & Horak, 1978)
• Molecular studies (Terrazas 2000; Crozier 2005) support a core monophyletic clade
• Some species (e.g. S. aragonii, S. eichlamii) are misplaced and likely belong elsewhere
• Seed morphology studies confirm heterogeneity
• Nyffeler & Eggli (2010): genus not fully monophyletic as currently circumscribed
• Guiggi (2012): suggests transferring problematic taxa to Marshallocereus

Despite these issues, the genus is maintained in a practical sense in Lodé (2015).

Species

According to Joël Lodé (2015):

• Stenocereus alamosensis
• Stenocereus beneckei
• Stenocereus chacalapensis
• Stenocereus chrysocarpus
• Stenocereus eruca
• Stenocereus fimbriatus
• Stenocereus fricii
• Stenocereus griseus
• Stenocereus gummosus
• Stenocereus humilis
• Stenocereus kerberi
• Stenocereus martinezii
• Stenocereus montanus
• Stenocereus pruinosus
• Stenocereus queretaroensis
• Stenocereus quevedonis
• Stenocereus standleyi
• Stenocereus stellatus
• Stenocereus thurberi
• Stenocereus thurberi subsp. littoralis
• Stenocereus treleasei

Notes

• One of the most ecologically and morphologically diverse cactus genera.
• Many species produce edible fruits important to local communities.
• Displays one of the widest pollination syndromes in Cactaceae.
• Includes anomalous taxa requiring further phylogenetic clarification.
• Central genus in the evolution of New World columnar cacti.