Potter and Oh Many plant groups distributed only in eastern Asia and temperate North America have long attracted the interest of botanists and have been the subject of numerous taxonomic, biogeographic, and evolutionary studies over the past two centuries. Despite this long history of interest and several recent phylogenetic studies of such plant groups, their biogeographic history has not yet been well established. Tribe Neillieae, comprising three taxonomically difficult genera, Neillia, Physocarpus, and Stephanandra, is distributed in eastern Asia and both eastern and western North America, usually in mountainous regions. Tribe Neillieae possesses ideal characteristics for studying historical biogeography of eastern Asia and temperate North America: the tribe is a strongly supported natural group, its distribution can be dissected into many areas in each continent, and its small number of species (ca. 25) facilitiates the analysis of a variety of data using a range of modern phylogenetic methods. However, no comprehensive systematic study of the group has yet been undertaken. Graduate student Sang-Hun Oh, under the direction of Dr. Daniel Potter at University of California, Davis, is studying phylogenetic relationships of the tribe Neillieae using morphological and molecular data. Four DNA regions, encompassing both nuclear and chloroplast genomes, for all species in tribe Neillieae will be analyzed along with morphological characters to estimate a maximally robust phylogenetic framework. Biogeographic history of the tribe Neillieae will be evaluated using this phylogenetic framework in conjunction with current distribution patterns and fossil records. A taxonomic revision with a sound classification system that reflects evolutionary relationships of the members of tribe Neillieae will also be provided. The historical biogeography of tribe Neillieae will provide important information relevant to understanding how and when the eastern Asian-North American disjunct distribution pattern developed. In addition, considering that plants of Neillieae are horticulturally useful, this study will provide valuable information for screening germplasm and developing new ornamental cultivars. Finally, by integrating several close relatives of the tribe Neillieae, data produced in this project will contribute to illuminating the evolutionary relationships within Rosaceae, an evolutionarily complex and economically important plant family.
