Phylogenetic, Biogeographic, and Monographic Studies of Asian Core Araliaceae

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Previous biogeographic studies of the Northern Hemisphere have emphasized the relationships of eastern Asia to other major areas, such as eastern North America, western North America, Europe, and western Asia. Biogeographic patterns within eastern Asia, however, have rarely been investigated using modern phylogenetic evidence. Most intercontinental studies treat the vast area of eastern Asia (often including the Himalayas) as a single biogeographic unit or an area of endemism, but this is certainly a gross oversimplification. Many floristic observations and studies clearly demonstrate that eastern Asia is biogeographically very diverse. In turn, the lack of testable hypotheses for biogeographic patterns within Asia has hindered more general understanding of the evolution of intercontinental biogeography of the Northern Hemisphere. The proposed study intends to employ a large Asian group of the plant family Araliaceae (the ginseng family) as a model to examine biogeographic relationships within Asia, emphasizing eastern and South Asia and the Himalayas. This region is herein referred to as "Asia" for the convenience of discussion. This "Asian Araliaceae group" comprises about 18 genera with a wide distribution throughout "Asia," and several of the subgroups within the Asian Araliaceae exhibit parallel distributional patterns across this region of interest. Thus, the Asian Araliaceae represent an ideal system to examine both individual and general biogeographic patterns within "Asia". The goals of the proposed study by Dr. Jun Wen and her colleagues in the U.S. and China are to (1) construct a robust genus-level phylogeny (evolutionary or genealogical relationships) of the Asian Araliaceae based on evidence from morphology, nuclear ribosomal DNA, and chloroplast DNA; (2) construct species-level phylogenies for two major lineages of the Asian Araliaceae: the Eleutherococcus - Macropanax - Metapanax group and the Brassaiopsis - Trevesia - Hedera group using four molecular data sets (sequences of nuclear ribosomal ITS, and chloroplast ndhF, atpB-rbcL spacer and trnC-trnD regions); (3) examine the biogeographic relationships of eastern and South Asia and the Himalayas based on phylogenies of at least three lineages of Araliaceae in this region (two groups mentioned above, and the Aralia - Panax complex currently being investigated by Dr. Wen); (4) re-evaluate the traditional taxonomic classification and generic delimitations of taxa within the Asian Araliaceae, including an assessment of morphological character evolution; and (5) provide a monograph of Aralia sect. Pentapanax, including the establishment of an internet page on the systematics of the Asian Araliaceae. Results from the proposed study will have several important implications. This will be one of the first studies to examine the biogeography of the vast region of eastern and South Asia and the Himalayas using a phylogenetic framework for a particular plant group. The phylogenetic analyses of the Asian Araliaceae will facilitate further systematic, evolutionary, and biogeographic studies in Asia as well as in the ginseng family worldwide.