The Phylogenetic Significance of Fruit Structures in the Family Cornaceae of China and Related Taxa

The fruit morphological structures of the Cornaceae of China and related taxa were studied using the wax GMA semi-thin section method and other methods to identify characters useful in delimiting clades circumscribed in previous molecular phylogenetic studies. Maximum parsimony analyses of 27 fruit structural characters resulted in a generally poorly resolved strict consensus tree, yet one whose major clades matched those revealed previously. Cornaceae of China and related taxa are recognized in four significant clades with the following fruit structural features: (1) Helwingia, fruits lack trichome, the abdominal vascular bundles are close to the endocarp, and the endocarp sclereid is elongated; (2) Aucuba, single-cell lanceolate trichomes, pericarp without secretory structure; (3) Torricellia, polygon and elongated sclereids in the endocarp, pericarp without crystal and tannin; and (4) Cornus sensu lato, the trichome is T-shaped, the abdominal ventral bundle is absent, and the endocarp sclereid is nearly round. In Cornus sensu lato, this document supported that the cornelian cherries (CC, subg. Cornus) and the big-bracted dogwoods (BB, subg. Syncarpea) are sister groups. The dwarf dogwoods (DW, subg. Arctocrania) are sister to them, and the blue- or white-fruited dogwoods (BW, subg. Kraniopsis, subg. Yinquania, and subg. Mesomora) are the base of the Cornus sensu lato clade. The number of cell layers of endocarps and the types of crystals afford sound evidence for identifying their relationship. This study indicated that the fruit structures of Cornaceae might provide morphological and anatomical evidence for molecular phylogeny.