Gaertnera (Gaertnereae, Rubiaceae) is a well-defined genus of approximately 70 species, with a paleotropical distribution encompassing Western Africa, Madagascar, Mascarenes, Sri Lanka and Southeast Asia. In addition to its wide geographical range, the genus also exhibits a large degree of morphological diversity, and is one of only twelve angiosperm genera in which dioecy has evolved from distylous ancestors. Prior to testing predictions from two alternative hypotheses for the evolution of dioecy in ancestrally distylous taxa it is necessary to reconstruct a phylogenetic estimate for the genus. Molecular phylogenetic estimates for Gaertnera are presented based on sequence data from 30-40 species for three nDNA markers; ITS (Internal Transcribed Spacer), Tpi (Triose phosphate isomerase) and PepC (Phosphoenolpyruvate carboxylase). Counter to our expectations based on the morphological differences and geographical separation between the sampled species, all markers reconstruct a rapid radiation for the genus. A combined analysis of all three markers will be discussed, in addition to molecular clock estimates for the divergence time of Gaertnera from its South American sister taxon, Pagamea.

Key words: Gaertnera, ITS, low-copy markers, PepC, Rubiaceae, Tpi