XVI International Botanical Congess

Within the subfamily Cactoideae, the members of the Cacteae represent the barrel cactus' group native primarily to North America. The group is morphologically diverse and no previous phylogenetic studies have been presented in the literature. We have examined ca. 50 representative taxa from throughout the tribe using sequence variation in the plastid rpl16 intron. Systematic implications of the phylogeny generated are that 1) the Cacteae form a monophyletic clade, 2) stem tubercles represent a derived condition, 3) as presently circumscribed, Mammillaria is paraphyletic and the generic status of Cochemiea, Escobaria, Pelecyphora and Coryphantha are in need of reevaluation. Additionally, support for retaining previously proposed subtribal groups is examined.