Phylogenetics and Biogeography of Lepechinia (Lamiaceae), and Evolutionary Studies within the Mentheae Tribe

The genus Lepechinia (Salviinae; Nepetoideae; Lamiaceae) is composed of about 42 species that range from Northern California to Central Argentina. Several species within the genus are important in indigenous culture in North and South America. The monotypic genus Neoeplingia, known only from the type locality and formerly placed in the subtribe Menthinae, is shown to be a member of the genus Lepechinia. Likewise, the rare monotypic genus Chaunosioma is shown to be embedded within Lepechinia.;Within the tribe Mentheae, four chloroplast and two nuclear ribosomal DNA markers were used to construct a comprehensive phylogeny. Previously accepted subtribal delimitations are shown to be paraphyletic and are updated. Two new subtribes, Lycopinae and Prunellinae, are described. Several genera within the Mentheae are shown to be paraphyletic, and taxonomic considerations are discussed. The crown of the Mentheae dates to the early-mid Eocene, and originated in the Mediterranean region. Within the subtribe Menthinae there was one major dispersal event to the New World during the mid-late Miocene. This New World clade has diversified rapidly since the late-Miocene and has radiated across North and South America.;Four chloroplast and seven nuclear markers were used to infer phylogenetic relationships within Lepechinia. Three main clades were recovered, corresponding broadly with geographical distribution. Lepechinia began to diversify in the middle-Miocene, perhaps as a response to global climate trends, and appears to have a Meso-American center of origin. Hybridization has played a major role in shaping the genus, particularly in South America. Dioecy is shown to have occurred multiple times within Lepechinia , sometimes - but not always - from gynodioecious ancestors.;Lepechinia and four other genera of the subfamily Nepetoideae are used as part of a Lamiaceae-wide phylogeny to evaluate historical biogeography hypotheses concerning the rise of the California Floristic Province proposed by Raven and Axelrod. We show that the California Floristic Province clades of Lepechinia and Salvia have sister groups of Madrean origin and were present in California since the middle Miocene. All five of the genera have experienced rapid radiations since the Pleistocene, probably as a result of recent climatic and orogenic changes within the CFP.