The longstanding problem of resolving relationships between Araliaceae and Apiaceae has been confounded by difficulties in interpreting patterns and polarities of morphological characters, leading to distinctly different taxonomic arrangements of this family pair. Recent molecular evidence has suggested that most taxa from Araliales fall into two “core” groups, corresponding largely to the traditional familial circumscriptions. The only representatives to fall outside of these core groups were some members of apiaceous subfamily Hydrocotyloideae and two araliads, Delarbrea and Mackinlaya. Among these “outlyer” taxa are found most of the troubling morphological features that have hampered past attempts at phylogeny reconstruction. In the present study, matK sequences were derived from representatives of Delarbrea, Mackinlaya, and their presumed close relatives, Pseudosciadium, Myodocarpus, and Apiopetalum. Of these taxa, all but Mackinlaya and one species of Delarbrea are endemic to New Caledonia, a refugium for many ancient lineages of plants. Phylogenetic analysis suggests that Mackinlaya and Apiopetalum (plus two hydrocotyloids) form the sister clade to “core Apiaceae,” a placement supported by several inflorescence characters (compound umbels, clawed petals with inflexed tips). Delarbrea, Pseudosciadium, and Myodocarpus form a separate clade, the placement of which is unresolved. In some trees, this “Delarbrea group” is sister to “core Araliaceae,” whereas in others it forms a clade with Pittosporaceae. The placement of the Delarbrea group is of special importance given its odd mixture of apiaceous and araliaceous features, including woody habits, bicarpellate fruits with oil-cells and woody endocarps, and in the case of Myodocarpus, compound umbels and schizocarpic fruits. Preliminary results from this study of New Caledonian endemics suggest (1) that these genera represent ancient lineages within Araliales, (2) that many character states once presumed to be derived may be ancestral, and (3) that Apiaceae (minus some hydrocotyloids) do not appear to be derived from within Araliaceae.

Key words: Apiaceae, Araliaceae, Araliales, matK sequence data, molecular phylogenetics, New Caledonian endemics