Acanthocalycium

Acanthocalycium
File:Acanthocalycium spiniflorum.jpg
Kingdom	Plantae
Family	Cactaceae
Subfamily	Cactoideae
Tribe	Cereeae
SubTribe	Trichocereinae
Genus	Acanthocalycium
Species
Notes	Taxonomy follows Joël Lodé (2015) with molecular insights from Arakaki (2003), Bárcenas et al. (2011), Hernández-Hernández et al. (2011), and Schlumpberger & Renner (2012).

Etymology

The name Acanthocalycium means “spiny calyx”, referring to the floral tube covered with spiny scales.

Description

Acanthocalycium is a genus of mostly solitary cacti with ribbed stems and characteristic spiny floral tubes.

• Habit: Usually solitary; globose to shortly cylindrical; apex often depressed.
• Roots: Fibrous to somewhat thickened.
• Stems: Green to grey-green; compact.
• Ribs: Well-defined, acute, often tuberculate.
• Areoles: Closely spaced along ribs.
• Spines: Straight, acicular to subulate; variable in number and length.
• Flowers: Diurnal, subapical; funnel-shaped to campanulate; white, pink or red.
• Floral tube: Covered with spiny scales (diagnostic feature).
• Pollination: Mainly by bees and sphingid moths; rarely by hummingbirds.
• Fruits: Spherical, hard; with persistent scales; dehiscent vertically.
• Seeds: Brown to black, papillose; hilum depressed.
• Dispersal: By water (hydrochory).

Habitat

Occurs in arid to semi-arid mountainous environments:

• rocky slopes and hillsides
• dry valleys
• grasslands and shrublands

Growing in full sun or partial shade among shrubs.

Altitude range: approximately 300–3300 m.

Distribution

Argentina:

• Catamarca
• Córdoba
• La Rioja
• Salta
• San Luis
• Tucumán

Taxonomy

The genus has undergone significant reclassification.

Key points:

• Established by Backeberg (1936) from taxa previously included in Echinopsis
• Often merged into Echinopsis sensu lato in broader classifications
• Arakaki (2003): supported recognition of the genus
• Bárcenas et al. (2011): confirmed separation of related taxa from Echinopsis
• Schlumpberger & Renner (2012): accepted the genus but noted paraphyly
• Hernández-Hernández et al. (2011): showed distinct phylogenetic placement

The genus is retained as distinct following Lodé (2015).

Species

According to Joël Lodé (2015):

• Acanthocalycium ferrari
• Acanthocalycium glaucum
• Acanthocalycium klimpelianum
• Acanthocalycium spiniflorum
• Acanthocalycium thionanthum

Notes

• Exhibits significant variability in spine morphology and flower coloration.
• Some taxa may represent closely related populations rather than clearly distinct species.
• Shares evolutionary proximity with other genera of Trichocereinae, but remains morphologically distinct.