Phylogenetics and Classification of Cunoniaceae (Oxalidales) Using Chloroplast DNA Sequences and Morphology

A phylogeny and revised classification of the flowering plant family Cunoniaceae and related taxa is presented. Parsimony cladistic analyses, including bootstrap and decay analyses, of chloroplast DNA sequences from two loci, trnL-trnF and rbcL, and morphology show that three genera often placed in their own families, Bauera, Davidsonia, and Eucryphia, are nested within Cunoniaceae. Brunellia may be most closely related to the Australian pitcher plant Cephalotus, and Aphanopetalum is in Saxifragales. Within Cunoniaceae, the New Guinean-South Pacific genera Acsmithia and Spiraeanthemum form a sister clade to the rest of family. Within this larger clade is a basal grade in which flowers mature centrifugally on an inflorescence axis, and a clade in which flowers mature synchronously to acropetally on an inflorescence axis. Other conspicuous morphological characters, including stipule position, inflorescence form, petal presence or absence, number of pollen colpi, carpel number, and fruit morphology, are homoplasious among and within clades at the tribal level. The results are used to propose a circumscription of the family, with 26 genera and approximately 300 species. Twenty genera are placed among six tribes (Cunonieae, Codieae, Geissoieae, Caldcluvieae, Schizomerieae, and Spiraeanthemeae), and six poorly resolved genera are not placed into any formally named group. Among outgroups, the Australian endemic family Tremandraceae is nested within Elaeocarpaceae.