Meeting Abstract

28.2  Jan. 5  Phylogeography of Astrotoma agassizii from South American and Antarctic waters using mtDNA HUNTER, Rebecca L.*; HALANYCH, Kenneth M.; Auburn University, Auburn, AL; Auburn University, Auburn, AL belchrl@auburn.edu

The isolation of the Antarctic continent has been a driving evolutionary force for Antarctic fauna for ~40 million years. Separation of Antarctica and South America, followed by the onset of the Antarctic Circumpolar Current (ACC), is presumed to be one of the primary forces driving speciation in the Southern Ocean. Despite this geographic and thermal isolation, some benthic marine taxa exhibit surprising levels of non-endemism. We therefore wanted to examine evolutionary relationships between Antarctic/subantarctic and South American benthic marine invertebrates due to the variety of potential isolating factors existing between these geographic localities. In this study, we looked at relationships among populations of the ophiuroid Astrotoma agassizii from both South America and Antarctica. Two mitochondrial genes were used to address questions regarding levels of divergence and gene flow among populations spanning the ACC. According to preliminary data for the 16S rDNA gene, low levels of sequence divergence (<4%) were observed between individuals occurring on both sides of the ACC. Two clades, corresponding to individuals collected from several stations in Argentine waters, were almost as divergent from one another as from the Antarctic clade. These relationships, coupled with low sequence divergences, suggest that gene flow occurred between these populations long after Antarctica and South America began drifting apart. Given the biology of A. agassizii, which likely includes a planktonic larval stage, larval dispersal is the likely mechanism by which gene flow occurred.