The Empetraceae comprises three genera: Empetrum L., Ceratiola Michx., and Corema D. Don. Empetrum has an antitropical distribution; Ceratiola is endemic to southeastern US; and Corema is disjunctly distributed in northeastern North America (C. conradii), Portugal and Spain (C. album), and the Azores (C. album var. azoricum). A cladistic analysis of the Empetraceae using 28 morphological characters placed Ceratiola in alternate positions, with either Empetrum or Corema. This led to the hypothesis that Ceratiola might be a hybrid between ancestors of Empetrum and Corema (Anderberg 1994). In this study we used sequences of nrDNA ITS and chloroplast gene matK to evaluate the monophyly of Empetrum and Corema, and to examine phylogenetic relationships of the Empetraceae. Ten samples were used representing the monotypic Ceratiola, species and subspecies of Corema, and species of Empetrum from both Southern and Northern Hemispheres. Sequences of four species of Rhododendron were withdrawn from the GenBank and were used as outgroups. In both matK and ITS trees, species of Empetrum form a clade that is sister to the strongly supported clade containing both Corema and Ceratiola, suggesting that Ceratiola may not be of a hybrid origin between ancestors of Corema and Empetrum. In the matK tree, Corema conradii is more closely related to Ceratiola than to Corema album and C. album var. azoricum, whereas in the ITS tree, Ceratiola is weakly allied with Corema album and C. album var. azoricum. This suggests that Ceratiola might be a hybrid between ancestral populations of Corema conradii, as a maternal parent, and C. album, as a paternal parent.

Key words: Ceratiola, Corema, Empetraceae, Empetrum, hybrid, matK, nrDNA ITS, phylogeny