Patterns of connectivity between the Lake Eyre and Gulf drainages, Australia: a phylogeographic approach

Historical barriers to dispersal in freshwater environments can be detected in the genetic structure of organisms living within these environments. Over time, it is possible that a barrier for freshwater organisms becomes passable, allowing gene flow between adjacent populations. The Lake Eyre and Gulf of Carpentaria Basins are adjacent drainages in northern Queensland. Low topography and large-scale flooding events make it possible that connectivity events may have occurred between the drainages throughout history. Documented geological evidence also suggests historical connectivity between the basins in the Pliocene. The present study looked at two widely distributed species, the freshwater fish Nematalosa erebi and the freshwater prawn Macrobrachium australiense, and used mitochondrial sequence data to assess past connectivity between the basins and estimate the timing of these events. Both species showed significant divergence across the drainage divide. There was evidence of two fragmentation events in the N. erebi data and divergence estimates for these events were 160 000 and 350 000 years ago. It was estimated that there has been no dispersal of M. australiense across the drainage divide for over one million years. The discordant evolutionary histories observed suggest that the patterns reflect recent historical environmental events and life- history differences between the two species.