The influence of landscape on population structure of four invertebrates in groundwater springs

1. The unique aquatic fauna of the island-like groundwater springs of arid inland Australia raises important questions as to how aquatic species persist in very isolated and fragmented habitats and the role that dispersal may play in mitigating ⁄mediating the influence of landscape structure and determining population structure. By determining the relationship between genetics and geography (i.e. phylogeography), the historical processes responsible for population structure can be determined. 2.We undertook comparative phylogeographic studies of invertebrates from springs south of Lake Eyre. Clusters of springs lying within and between surface drainage catchments (which provide a potential connection between springs) were sampled, and the phylogeographic structure of four coexisting species, an ostracod Ngarwa dirga, a snail Fonscochlea accepta, an isopod Phreatomerus latipes and an amphipod Wangiannachiltonia guzikae, was examined. 3. Clear differences in the geographic patterns of genetic structure were found amongst the four species. No discernable genetic structure was found in ostracod and snail populations, even amongst springs lying 20 km apart in separate surface catchments; isopod populations were highly genetically structured amongst springs located in separate catchments, but not within catchments, whilst amphipod populations were highly genetically structured amongst springs both within and between catchments. 4. The results suggest that differences in dispersal ability of each species, and not the overall fragmented nature of the springs, may have led to large differences in phylogeographic history. Interestingly, the relative dispersal ability of these species may be related to their vulnerability to and recovery from large-scale flood events. Therefore, despite the highly isolated and fragmented nature of the springs, the landscape has not strongly influenced the population structure of the aquatic invertebrate community as a whole nor has it led to the evolution of common life histories.Nicholas P. Murphy, Michelle T. Guzik and Jessica Worthington Wilme