The classic biogeographic disjunct pattern, known as "the Tertiary relict disjunction", has been of interest to botanists for a long time, since the time of Linnaeus. The genus Osmanthus, with its more than 25 species, demonstrates this classic disjunct pattern, with a majority of the species of this genus represented in eastern Asia, and the others in northern Turkey and in south eastern United States. Green (1958) examined this genus thoroughly in his monograph primarily based on morphological evidence. In our study, we conducted a phylogenetic analysis to infer relationships among the species of Osmanthus by using nuclear ribosomal ITS DNA sequences. We sampled taxa from all the sections recognized by Green (1958). After constructing the phylogeny of the genus based on ITS DNA sequences, we compared current distribution of the genus with inference from the DNA molecules and generated biogeographic patterns for Osmanthus species.

Key words: Osmanthus , biogeography, ITS, Oleaceae, phylogeny, Tertiary disjunction