9615211 BURRESON The phylum Annelida is an extremely diverse assemblage of terrestrial, freshwater and marine worms. The phylum is divided into two main groups. In one group, which includes the branchiobdellidans, hirudinea (leeches) and oligochaetes (earthworms and relatives), the worms have a glandular clitellum that secretes a protective cocoon around the eggs. In the other, which includes the polychaetes, the worms lack a clitellum. Although the ecological significance of the hirudinean and oligochaete worms is well established, they are among the most poorly studied invertebrates with respect to their historical relationships (phylogeny). In this study, Eugene Burreson and colleagues will collect data from morphology and from both mitochondrial and nuclear gene sequences, and use these data to reconstruct the phylogeny of non-polychate annelids. Analyses will include separate investigations of relationships among leeches, among branchiobdellidans, and among oligochaetes, as well as more inclusive analyses involving all individuals in all three groups. The latter analysis should answer long-standing questions on the origin of the branchiobdellidans and leeches from oligochaete or polychaete ancestors. The research should yield robust phylogenies that serve as a foundation for subsequent studies on the life history patterns of these organisms.
