Sequences of the internal transcribed spacers of nuclear ribosomal DNA were used to estimate phylogenetic relationships within Stewartia. Eighteen samples were included, representing two species of Hartia, seven species of Stewartia, and an outgroup, Franklinia alatamaha. Several different inference methods were used, including parsimony, neighbor-joining, and maximum likelihood. Parsimony analyses were conducted treating gaps as missing data or as a fifth character state. In all analyses Hartia sinensis and H. villosa form a clade that is the sister group of Stewartia. Within Stewartia the New World and the Old World species form well supported clades. The subgenera and sections of Stewartia proposed by previous authors are not supported by our ITS data. Two clades are recognized within the Old World lineage: S. serrata+S. rostrata; and S. pseudocamellia+S. monadelpha+S. sinensis. A comparison of levels of sequence divergence suggests that southeast Asia and China may be a recent center of diversification in Stewartia. Morphological disparity between the North American Stewartia species is much higher than it is among the larger number of Asian species.

Key words: biogeography, Hartia, morphological disparity, nrDNA ITS, phylogeny, Stwartia, Theaceae