Book excerpt: Salvia subgenus Calosphace (Lamiaceae), the largest of 5 subgenera with some 500 species and strongly supported as monophyletic, has received no comprehensive systematic research since the initial establishment of 91 taxonomic sections. Representative taxa of 73 sections of Calosphace were sampled to investigate the phylogenetic relationships and identify major lineages using chloroplast (intergenic spacer, psbA-trnH) and nuclear DNA (ribosomal spacer region, ITS). Phylogenetic analysis of the combined data set established the monophyly of nine sections (Blakea, Corrugatae, Dusenostachys, Erythrostachys, Hastatae, Incarnatae, Microsphace, Nobiles, and Sigmoideae) and four major lineages (S. axillaris, "Hastatae clade", "Uliginosae clade", and "Core Calosphace") corresponding with the four major stamen types identified within the subgenus. Disjunct sections spanning two or more centers of diversity are not supported by the results; no more than seven dispersal events to South America are required to account for the current disjunct distributions. One member of the subgenus, Salvia divinorum is hallucinogenic and used in traditional healing ceremonies by the Mazatecs of Mexico. It was classified within section Dusenostachys and hypothesized to be an interspecific hybrid. Multiple DNA regions (ITS, trnL-trnF, and psbA-trnH) of 52 species representing the major lineages of subgenus Calosphace and six accessions of S. divinorum were sequenced to test its phylogenetic position and putative hybridity. Salvia divinorum should not be classified within Dusenostachys nor is it a hybrid according to the results; its closest relative is S. venulosa, a Colombian endemic. In addition to S. divinorum, there are many other Calosphace species that are used medicinally in North and South America. Ethnobotanical data was gathered for 150 species; those sharing the common names, medicinal uses, appearances, and similar compounds associated into medicinal plant complexes. Five new, previously undocumented complexes were identified: Mirto (5 spp. used extensively in the treatment of susto and other illnesses in Mexico), Ñucchu (7 spp. used as a symbolic element in religious processions and in the treatment of respiratory ailments in Peru), Lí'l ++ (3 spp. used for food and medicine by the Chianantec), Cantueso (2 spp. used for respiratory ailments in Mexico), and Manga-paqui (3 spp. used for kidney and liver problems in Ecuador).