Islands of water in a sea of dry land: hydrological regime predicts genetic diversity and dispersal in a widespread fish from Australia’s arid zone, the golden perch Macquaria ambigua
Faulks, L.K., Gilligan, D.M. and Beheregaray, L.B., 2010. Islands of water in a sea of dry land: hydrological regime predicts genetic diversity and dispersal in a widespread fish from Australia’s arid zone, the golden perch Macquaria ambigua. Molecular Ecology, 19(21): 4723–4737.
Exploring patterns of gene flow is the key to understanding population dynamics and spatial population structure. In freshwater environments, gene flow is restricted by the spatial hierarchy of the drainage network and by temporal variation of connectivity within the network. In the Australian arid zone, this variability is high and rivers often exist as isolated waterholes connected only during unpredictable floods. These conditions cause boom and bust cycles in the population dynamics of taxa, but their influence on patterns of gene flow is largely unknown. We used a landscape genetics approach to assess the effect of hydrological variability on gene flow in an iconic Australian freshwater fish, Macquaria ambigua. Despite temporal isolation of populations, the species showed high rates of dispersal, with genetic structure only evident among populations from major drainage basins. Within drainages, hydrological variability was a strong predictor of genetic diversity. Our modelling procedure indicated that genetic diversity was positively correlated with spring flow volume and perenniality. We propose that increases in flow volume during spring stimulate recruitment booms and dispersal, boosting population size and genetic diversity and that perenniality helps maintain genetic diversity. Although it is uncertain how the hydrological regime in arid Australia may change under future climate scenarios, management strategies for arid zone fishes should mitigate barriers to dispersal and alterations to the natural flow regime to maintain connectivity and the species evolutionary potential.