BELCHER, R.L.; HALANYCH, K.M.*; Auburn University; Auburn University: Phylogeography of ophiuroids from South American and Antarctic waters using mtDNA

The isolation of the Antarctic continent has been a driving evolutionary force for Antarctic fauna for ~25 million years. The separation of the Antarctic and South American continents and the onset of the Antarctic Circumpolar Current are presumed to have acted as primary forces driving the speciation of many marine taxa. Despite this geographic and thermal isolation, some benthic marine taxa exhibit surprising levels of non-endemism. We therefore wanted to examine evolutionary relationships existing between Antarctic/ subantarctic and South American benthic marine invertebrates due to the variety of potential isolating factors existing between these geographic localities. We looked at relationships among three ophiuroid species, two Antarctic species from the genus Ophiurolepis and one South American species questionably assigned to the genus Homalophiura. Two mitochondrial genes were used to answer questions regarding levels of divergence, morphological relationships and endemicity. Our sequence data did not uphold traditional relationships based on morphology for the three species. It was found that the two sympatric Ophiurolepis species from within Antarctica were less closely related and more genetically divergent than one of the Ophiurolepis species was with the South American Homalophiura species. The assignment of the South American species to a separate genus has been debated in the taxonomic literature thus showing how molecular data can help to resolve existing taxonomic problems. These results indicate either that the two Antarctic species diverged prior to the separation of Antarctica and South America or that the two more closely related Antarctic and South American species maintained gene flow for some period of time after separation.