The 19 species of Graptopetalum (Crassulaceae) are succulent herbs occurring primarily in dry habitats from southwest Arizona in the United States to Oaxaca in southern Mexico. The genus is characterized by having leaves arranged in a rosette, a lateral inflorescence, fetid flowers with dots on the upper half of the rotated petals, and reflexed stamens. Graptopetalum has had a troubled taxonomic history, with several species being moved into it after having been described originally in other genera. The goal of this study is to analyze the relationships among species in the genus using nuclear and plastid DNA sequence data from ITS, the trnL intron, the trnL-trnF intergenic spacer, the rpl16 gene, and from morphological data. The molecular cladograms are poorly resolved, but our preliminary results indicate that there are a few supported clades within the genus. These include a clade containing G. glassii, G. pentandrum and G. superbum, which is well supported in all analyses. Morphological data alone separates the genus into two major clades: the caulescent and the acaulescent species. Although Graptopetalum was assumed to be monophyletic based on the synapomorphies of reflexed stamens, rotated petals in the upper half, and fetid flowers, molecular data position Tacitus bellus within the ingroup. This unexpected result will require further investigation.

Key words: Crassulaceae, Graptopetalum, ITS, molecular, morphology, Phylogeny, trnL-F