Classification, Origin, and Patterns of Diversification of Corynocarpus (Corynocarpaceae) Inferred from DNA Sequences

Sequences from the chloroplast-encoded gene rbcL and the nuclear-encoded internal transcribed spacer (ITS) region were analyzed independently and then combined to infer phylogenetic relationships of Corynocarpus. Relationships obtained from the rbcL and ITS data sets are are largely congruent and well resolved. The combined data set provides even greater support for relationships. The rbcL results support current placement of Corynocarpus in its own distinct family, the Corynocarpaceae, and suggest that this family is most closely related to the Anisophylleaceae, Begoniaceae, Coriariaceae, Cucurbitaceae, Datiscaceae, and Tetramelaceae, together comprising the order Cucurbitales. This contradicts traditional classifications, which have placed the Corynocarpaceae in the Celestrales. The five species of Corynocarpus are genetically distinct, but comparison of ITS sequences shows little infraspecific sequence variation within C. laevigatus and C. rupestris. The present distribution, fruit morphology, and patterns of relationships inferred from the sequence data suggest a Palaeotropical center of origin and two independent radiations in the Corynocarpaceae. The first radiation comprises C. cribbianus and C. rupestris, which extend through New Guinea to Australia, and the second radiation comprises C. dissimilis and C. laevigatus, which extend southwards through New Caledonia to New Zealand. Communicating Editor: John V. Freudenstein