Conradina (Lamiaceae) is a genus of plants endemic to the southeastern U.S. consisting of six allopatric species that differ in distribution. Conradina species are found only in scrub with white sand or rocky soil and require frequent disturbance regimes to clear areas for establishment. Because of fire suppression and high specificity to a habitat that is quickly being destroyed, many of these species are highly endangered. Four species, C. etonia, C. glabra, C. verticillata, and C. brevifolia are federally endangered or threatened. Although many Conradina species have federal recovery programs, they are closely related and there is considerable controversy over the taxonomy of this genus. For example, recent morphological analyses of the federally endangered C. brevifolia suggest that this species is a possible ecotype of the more widespread C. canescens (Chafin 2000, Crook 1998), and thus may not deserve federal protection. Furthermore, populations of plants that are intermediates between C. canescens and the federally endangered C. glabra have been a source of confusion to many Florida botanists and may be in need of description and protection. Although morphological analyses have attempted to answer these questions, the results have been inconclusive. The purpose of this study was to re-evaluate Conradina using molecular systematic techniques to reassess the validity of each species and to understand the evolutionary history of the genus. A molecular phylogeny was reconstructed using the ITS region of 18S-26S ribosomal genes and trn L-T and matK from the chloroplast genome; species of the related Calamintha were used as outgroups.

Key words: Conradina, ITS, Lamiaceae, matK, molecular phylogeny, trn L-T