BABBITT, C.C.; PATEL, N.H.; University of Chicago; University of Chicago: Phylogenetic relationships within the Malacostraca (Crustacea) based on 18S and 28S rDNA sequences

The Malacostraca is the most speciose and morphologically diverse class in the Crustacea, with approximately 30,000 described species. However, because of this diversity in body plan it has been proposed that morphological characters in malacostracan systematic studies may be confounded by parallel or convergent evolution. Molecular phylogenetic studies would be a way to both test possible morphological convergences and to add new lines of evidence to strengthen the phylogenetic hypotheses. Yet, to date, few molecular phylogenetic analyses have been done for this group. Some of the major questions about the relationships within the Malacostraca are: Is the Leptostraca the sister group to the rest of the Malacostraca? What is the relationship between the five major groups (Hoplocarida, Phyllocarida, Syncarida, Peracarida, and Eucarida) within the Malacostraca? Is the Peracarida monophyletic? Are the Amphipoda and Isopoda sister groups? We will present 18S and partial 28S rDNA data to help answer some of these questions. We collected and sequenced 60 species within the Malacostraca representing 29 families, with heavy taxon sampling in the Peracarida. Nine other crustacean species were used as outgroups. Alignments were done with ClustalX and POY, and tree building was done using both parsimony and likelihood as the optimality criterion. Among some of our preliminary results are the placement of mysids as a basal group outside of the Peracarida, a sister group relationship between the Amphipoda and Isopoda, and a clarification of the relationships within the Amphipoda.