Each of the few studies of the phylogeography of southeastern Australian marine and brackish water environments has revealed further complexity. The complexity is likely due to the interaction of multiple factors including (i) the repeated challenges posed to fauna by environmental change in the Quaternary; (ii) intra-specific reproductive characteristics and responses to selection; and (iii) sporadic long-distance dispersal. A comparative understanding of gene flow in the region is important for management of MPAs. What is already known indicates, however, that much more research is required. Several studies of marine species have suggested that land-bridges across Bass Strait have had a prominent role in structuring genetic diversity in the region, but with conflicting inferences about timing. No study has closely identified the other principal biogeographic boundary in southern NSW with phylogeographic discontinuities.

Studies of segments of the mitochondrial 12S rRNA and nuclear ITS-1 genes of the two nominal species of the estuarine/lagoonal hydrobiid snail Tatea have revealed new diversity patterns. In 12S rRNA, the same common haplotype is found in both T. kesteveni and T. huonensis, ranging from Ballina in northern NSW to Perth, WA. Variant haplotypes differ from the common form at few bases and have restricted (although occasionally disjunct) distributions. In ITS-1, the most frequent haplotype is widely-distributed in both species and a second common wide-ranging type is found in T. kesteveni.

We will report the results of investigations of other estuarine species (including the pulmonate snails Phallomedusa and Salinator, and the mussel Xenostrobus securis) to determine whether the Tatea pattern is general in molluscs from this environment. We will also report on studies searching for novel phylogeographic breaks in marine species such as the mussels X. pulex and Brachidontes rostratus and the snails Siphonaria spp., Austrocochlea spp. and Bembicium spp.