Genetic data support independent glacial refugia and open ocean barriers to dispersal for the Southern Ocean sea spider Austropallene cornigera (Möbius, 1902)

The diversity and distribution of Antarctic life has been strongly influenced by climatic events, in particular by large scale extension of ice sheets onto the continental shelf during repeated glacial cycles. It has been suggested that populations of benthic marine biota in the Antarctic were limited to very few refugia because the Antarctic shelf was covered with ice. Using the broadly-distributed pycnogonid Austropallene cornigeraas a model, in this study we tested different hypotheses for possible locations of glacial refugia ( ex situon the peri-Antarctic islands or in situon the Antarctic shelf). We sampled 64 individuals of A. cornigerafrom peri-Antarctic islands, the Weddell Sea and East Antarctica. The phylogeographic structure was analysed using partial sequences of the nuclear ribolomal genes 18S and 28S and the mitochondrial cytochrome coxidase subunit I gene (COI). The 18S and 28S sequences were highly conserved. Sequences of the COI were variable and revealed highest haplotype diversity for populations on the Antarctic shelf and lowest for the population from the remote island of Bouvetøya. In addition, the data showed clear genetic distances between the island and shelf populations. Our data are consistent with the hypothesis of survival in situ. The results also suggest that gene flow within A. cornigerais limited, hinting at possible speciation processes acting independently on the Antarctic continental shelf and the peri-Antarctic islands.