Investigations that coordinate phylogenetic analyses with explorations of the evolutionary processes are essential for understanding organismal diversity. The proposed research, centered on the hydrangea family of plants, aims to resolve phylogenetic relationships among major groups of flowering plants. This will be accomplished by focusing on key taxa in conjunction with groups that are poorly known and considered "anomalous" in the subclass Rosidae, many of which are Asian in origin and poorly known in collections. Hydrangeaceae are positioned near the divergence of the subclass Asteridae, and this investigation will increase our understanding of evolutionary diversification preceding the origin of subclass Asteridae with its great floral conservation. The proposed investigation has three facets: 1. phylogenetic analysis using anatomical and morphological features of plants of the hydrangea and dogwood groups positioned taxonomically among Rosidae and near the origin of Asteridae; 2. phylogenetic analysis within the Hydrangeaceae family to distinguish natural groups of species and genera and to explore patterns of flower and fruit evolution in the family; and 3. ontogenetic or developmental studies to determine roles of various cellular processes in the evolution of different floral and fruit forms. An explicit phylogenetic framework will help guide the choice of critical taxa in making comparisons for the study of different developmental processes that create flower and fruit diversity.
