The awe with which most biologists view the organismal diversity of nature has contributed to several generations of study, yet biologists still do not understand in detail the evolutionary processes that generate this biological diversity. Theoretical models of speciation and diversification have been proposed, but few of these theories have been tested rigorously with empirical data from specific groups of plants and animals. The lack of experimental studies of speciation reflects in part an inability to recognize actively speciating groups, that is, those groups currently undergoing the processes of divergence and reproductive isolation. However, recent advances in the field of molecular biology and in phylogenetic data analysis have made possible the identification of such actively speciating groups. Dr. Pamela Soltis of Washington State University proposes to use these new methodologies (restriction site analysis of chloroplast DNA and cladistic methods of phylogenetic analysis) to reconstruct the evolutionary history of the 70-80 species of Lomatium, a genus of plants from western North America. Lomatium was chosen for study because it appears to be an actively speciating genus, with a large number of morphologically discrete species occupying very restricted geographic ranges. Furthermore, several models of speciation seem to fit general observations on Lomatium: geographical divergence, hybrid speciation, and polyploidy (chromosome doubling). The proposed research will provide a robust hypothesis of evolutionary relationships among all the species in the genus and will allow the identification of smaller subgroups of species appropriate for future experimental analyses of speciational processes and the biology of endemic (narrowly distributed) species.
