9623638 Simpson Graduate student Todd Barkman, with direction from adviser Beryl Simpson at the University of Texas, is studying an interesting problem in plant evolution and distribution in Southeast Asia. The focus of the project is the orchid genus Dendrochilum and the 20-30 species of subsection Eurybrachium that occur mostly on the large island of Borneo, with many on Mt. Kinabalu alone. Field collections will augment herbarium materials to enable detailed morphological study of vegetative and floral characters; field work capitalizes on the floristic inventory activities of Prof. John Beaman and his Malaysian and Indonesian colleagues. In addition, molecular (DNA) analyses of nuclear and chloroplast genes will add new data for measuring mutational differences between the species and for inferring phylogenetic relationships. Related groups on the islands of Sumatra, Java, and Sulawesi, and in the Philippines and Malaysia will also be studied for phylogenetic comparisons. A robust phylogeny of the species will test two competing hypotheses for the origin of these epiphytic orchids. One hypothesis claims adaptive radiation on Borneo from a single ancestral introduction; the second hypothesis claims multiple introductions from different islands around Borneo. %%% The integration of traditional morphological characters with new molecular data from DNA sequencing promises a more reliable taxonomy of plants and the robust inference of phylogenetic (genealogical) relationships among species. With this phylogeny in place, patterns of historical biogeography (migration, adaptive radiations, speciation) can be analyzed. Barkman and Simpson's study of Dendrochilum orchids is one further example of this rejuvenated plant systematics. ***
