For Chile Hunt (1999; CITES Cactaceae Checklist) recognizes 11 genera and about 80 species of Cactoideae (Cactaceae), of which six genera (Austrocactus, Copiapoa, Corryocactus, Eriosyce, Eulychnia, and Neowerdermannia) and about 65 species are traditionally regarded as closely related and referred to the tribe Notocacteae (Barthlott & Hunt 1993; Families and Genera of Flowering Plants). Molecular phylogenetic analyses based on chloroplast DNA markers (trnK intron, matK, trnL-trnF intron and spacer), however, reveal that these genera in fact are members of three different major clades of Cactoideae. Austrocactus, Eulychnia, and Corryocactus are related to basically West Andean representatives of the tribes Browningieae (excl. Browningia) as well as the Central and North American Hylocereeae, and Pachycereeae. Copiapoa represents a distinct basal lineage within Cactoideae without any obvious close relatives. Finally, Eriosyce and Neowerdermannia are related to the East Andean genus Parodia These findings indicate that the various similarities in different types of growth forms and related vegetative characters in the two most diverse Chilean genera, Copiapoa and Eriosyce, represent striking convergences. Biogeographically the cactus flora of Chile falls into two distinct parts with minimal overlap, (1) a narrow strip along the coast of the central and northern half of the country, comprising the coastal cordillera as well as some of the major inland valleys, and (2) the W slopes of the main cordillera of the extreme NE of the country. Representatives of the former area are Austrocactus, Copiapoa, Echinopsis, Eriosyce, and Eulychnia, while the genera Browningia, Corryocactus, Neowerdermannia, Oreocereus, and Weberbauerocereus are only present in the latter area. The exception to the rule is Haageocereus which is present with one representative in each of the two areas and Echinopsis atacamensis which occurs in area 2.

Key words: biogeography, Cactaceae, cacti, Cactoideae, Chile, phylogenetics