Taxonomy & identification

• Buxbaum (1958b) first described the tribe Cacteae (as Echinocacteae), defining it as a clear-cut phylogenetic unit comprising the short-columnar or globose North American cacti with spineless flowers, excepting Astrophytum which he placed in tribe Notocacteae. [Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation]
• Generic delimitation in Cacteae is uncertain: the CITES Cactaceae checklist (Hunt 1999) recognizes 23 genera (with at least 34 other genera described), accepting 314 species plus 224 provisionally accepted species; Anderson (2001) recognizes 26 genera and 384 species. [Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation]

Phylogenetics — the DNA story

• Parsimony analysis of plastid rpl16 intron sequences from 62 members of tribe Cacteae plus four outgroup taxa yielded 1296 equally parsimonious trees of length 666 steps; the strict consensus established a highly pectinate topology delimiting clades corresponding to several previously recognized generic groups. [Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation]
• The tribe Cacteae is supported as monophyletic with a decay value of 9 and 100% bootstrap support; no direct relationship was found with Bergerocactus emoryi (Pachycereeae) or with Notocacteae members (Parodia haselbergii, Corryocactus brachypetalus). [Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation]

Native range

• The geographic range of Cacteae extends from western Canada (Escobaria vivipara) to Colombia, Venezuela, and the Caribbean (Mammillaria colombiana and M. mammillaris), with maximal diversity in Mexico. [Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation]

History

• Buxbaum (1958b) recognized 36 genera in the tribe and defined four subtribes based on seed morphology: Echinocactinae (smooth hard black testa with conspicuous perisperm), Thelocactinae (verrucose mostly black testa becoming secondarily smooth or spotted), Ferocactinae (pitted or reticulate testa), and Coryphanthinae (smooth brown testa). [Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation]
• Backeberg's (1970) non-phylogenetic classification placed the North American barrel cacti in subtribe Boreocactinae (48 genera), reflecting his philosophy of recognizing many genera with few species each; many of these microgenera were later united into broader genera in modern treatments. [Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation]
• Barthlott and Hunt (1993) united several Cacteae genera, recognizing 22 genera in total: they included Homalocephala within Echinocactus and subsumed Oehmea, Cochemiea, Dolichothele, and Mamillopsis within Mammillaria. [Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation]

Conservation

• Glass (1998) treated Acharagma in a publication titled 'Guide to the threatened cacti of Mexico' (Cante AC, San Miguel de Allende, Guanajuato, Mexico), and generic listings for the tribe derive from the CITES Cactaceae Checklist (Hunt 1992, 1999), reflecting the tribe's relevance to cactus conservation listing. [Molecular Systematics of Tribe Cacteae (Cactaceae: Cactoideae): A Phylogeny Based on rpl16 Intron Sequence Variation]