My primary research focuses on the systematics, biogeography, and evolution of members of the flowering plant order Ericales, a group of about 23 plant families that includes many well-known plants such as blueberry, phlox, persimmon, primrose, and tea. Many of the plants in this order are disjunct relicts, which means that they were once (in the Tertiary period) widespread but are now restricted in range to discrete and widely separated areas of the earth due to climate change. These areas include California, southern Europe, eastern North America and eastern Asia. I use a combination of morphological and molecular approaches on ericalean groups to understand their species diversity, evolutionary relationships, and adaptations to particular environments. The patterns of relictualism and speciation elucidated from these studies can eventually lead to a better overall understanding of the effects and significance of climate change on the world's biota.
In collaboration with Frank Almeda (CAS-Botany) and other colleagues, I am currently concentrating on the genus Symplocos (Symplocaceae, the sweetleaf family, ca. 300 species). This clade has an amphi-Pacific tropical disjunction, meaning that it occurs in tropical regions (although with a few temperate outliers) in the Americas and the lands bordering the Pacific Rim, but nowhere else. It is generally assumed that amphi-Pacific tropical disjuncts arrived at their present distributions through migration across high-latitude land bridges in the Tertiary period, when global climate was much warmer than today. This idea is bolstered by Tertiary fossil fruits of Symplocos in North America and especially in Europe, where there appear to have been whole forest ecosystems dominated by Symplocos. A minority opinion holds, however, that these disjuncts can be accounted for by trans-oceanic tropical migration and that fossil sampling artifact has obscured the more widespread nature of these disjuncts.
We are currently testing these ideas in a phylogenetic context by analyzing DNA sequences of Symplocos species from throughout the distribution of the genus. Preliminary results are tending to support a Northern Hemisphere origin for the group with subsequent migration to South America. This pattern has also been found in Styrax (Styracaceae), another member of Ericales. Through international collaboration I am expanding studies on amphi-Pacific tropical disjuncts to include other members of Ericales such as Clethra (Clethraceae) and Gaultheria (Ericaceae, wintergreen) in an attempt to detect general patterns of intercontinental dispersal among these groups.
Within the context of this research I also conduct studies in floristics and taxonomy. I lead a long-term, large-scale survey and inventory of the biota of the Gaoligong Mountains in western Yunnan Province, China. This survey is documenting the land plants, arthropods, vertebrates, and Quaternary vertebrate fauna of this biodiversity. Three primary institutes form the primary collaboration in this project: the Kunming Institute of Botany, the Kunming Institute of Zoology, and the CAS. The project is discovering many new species to science and many new records for the region, and also is developing a comprehensive GIS-based data set for use in biogeographical analysis and conservation management strategies for the local government. My colleagues and I are preparing taxonomic treatments of various plant groups based on this research. This complements my past and current monographic studies and taxonomic revisions on Styracaceae and Symplocos (such as treatments for Flora of China, Flora Neotropica, and Flora of North America).
