The Polyalthia hypoleuca species complex (Annonaceae) is a group of six closely related (monophyletic) species that grow sympatrically in various combinations throughout the lowland tropical rain forests of Southeast Asia. Restriction enzyme activity variation of ribosomal and chloroplast DNA extracted from dried leaves will be investigated as a means of comparing genetic variation within and among populations of each species, and among species. DNA variation within and among populations of each species will not only be informative as to genetic variability in tree populations of the humid tropics, but will illuminate the constant genetic variation among species. This significant interspecific genetic variation will be analyzed cladistically (DNA of the most plausible outgroups will also be examined) to provide a molecular phylogenetic hypothesis for the P. hypoleuca complex, and this will be compared with a phylogenetic hypothesis derived from morphological data. The most strongly supported (congruent) phylogeny emerging from these analyses will be used to examine the radiation of the members of this group from a common ancestor with regard to ecological differentiation and biogeographical distributions of the species. Results will be interpreted in relation to the paleogeography of the region, and to hypothesized differences in evolutionary forces between tropical and temperate forests. Dr. Steven H. Rogstad will perform this postdoctoral fellowship research during two years of tenure at Washington University (St. Louis, MO).
