Crustaceans comprise a diverse arrray of arthropods that have come to inhabit nearly all possible habitats on earth, from mountain soils to the deep sea. Dr. Lawrence Abele has studied their evolution and ecology using morphological data from whole organisms and thin sections of tissue, as seen with light and electron microscopy. More recently, he has learned the most current molecular techniques for unravelling the evolutionary relationships among different crustacean groups. Dr. Abele proposes to analyze ribosomal RNA sequences of representative species from each of the major crustacean groups (including remipedes, branchiopods, cephalocarids, ostracodes, and crabs, to name a few). Evolutionary relationships will be reconstructed from these sequence data, and compared with patterns of relationships inferred from morphological data. The proposed research would have significant impact on a large and diverse audience of biologists. Crustacea have evolved a wide array of morphologies, behavior, and ecological habits, and the molecular study of their evolutionary history will provide a framework for understanding how, and when, and how often these various traits have appeared. These new and independent data will open new areas of research, and will deepen our understanding of the Crustacea and of the evolutionary process.