Zieria Sm. (Rutaceae, Boronieae) is predominantly native to eastern Australia except for one species, which is endemic to New Caledonia. For this study, sequence data of two non-coding chloroplast regions (trnL-trnF, and rpl32-trnL), one nuclear region (ITS region) and various morphological characters, based on Armstrong’s (2002) taxonomic revision of Zieria, from 32 of the 42 described species of Zieria were selected to study the phylogenetic relationships within this genus. Zieria was supported as a monophyletic group in both independent and combined analyses herein (vs. Armstrong). On the basis of Armstrong’s (2002) non-molecular phylogenetic study, six major taxon groups were defined for Zieria. The Maximum-parsimony and the Bayesian analyses of the combined morphological and molecular datasets indicate a lack of support for any of these six major taxon groups. On the basis of the combined Bayesian analysis consisting of molecular and morphological characters, eight major taxon groups are described for Zieria: 1. Z. cytisoides group, 2. Z. granulata group, 3. Z. laevigata group, 4. Z. smithii group, 5. Z. aspalathoides group, 6. Z. furfuracea group, 7. Z. montana group, and 8. Z. robusta group. These informal groups, except for of the groups Z. robusta and Z. cytisoides, correspond to the clades with posterior probability values of 100.
