Phylogenetic relationships in the Corylopsis complex (Hamamelidaceae): Evidence from sequences of the internal transcribed spacers of nuclear ribosomal DNA and morphology

Morphological and nuclear ribosomal Internal Transcribed Spacer (ITS) sequence data were used to examine relationships among the genera in the Corylopsis complex, comprising Corylopsis, Distylium, Eustigma, Foracnean's and Sinowilsonia. The ITS-2 based cladogram had the lowest resolution, whereas the ITS-1 and the pooled data of ITS-1 and ITS-2 produced similar phylogenies with complete resolution of intergeneric relationships within the complex. Both morphological data and ITS DNA sequences support separation of Corylopsis from the other genera, and a closer relationship of Sinowilsonia to Fortunearia than to Distylium. The monophyly of Eustigma-Fortunearia-Sinowilsonia was supported by the ITS sequence data. This study substantiates Endress's recent interpretation of the intergeneric relationships in the Corylopsis complex. The ITS phylogeny also supports the hypothesis that floral structures in members of the Corylopsis complex appear to have been modified for wind pollination in the course of evolution.