Divided by the range: evidence for geographic isolation of the highly mobile Emu (Dromaius novaehollandiae)

Conserving evolutionary processes is becoming increasingly important in conservation management as environmental changes threaten wild populations. Characterising genetically distinct populations and assessing connectivity across the landscape enables wildlife managers to prioritise conservation efforts with limited resources. In the NSW North Coast bioregion of Australia, one of the last remaining coastal populations of the Emu (Dromaius novaehollandiae) has been state-listed as an Endangered Population, owing to its geographic isolation and small census size. Using mitochondrial and nuclear genetic markers, we examined the spatial genetic structure of Emus across south-eastern Australia and assessed the effective population size (N_e) and genetic diversity of the NSW North Coast Emu to inform management. We show significant genetic divergence between the NSW North Coast Emu and other localities based on thousands of highly resolving nuclear markers, which was not explained by geographic distance. Among NSW North Coast Emus, we found less genetic diversity and a critically low effective population size (N_e = 14.84 and 22.49 based on independent methods). Together, these findings suggest that the NSW North Coast Emu is at risk of further losses of genetic diversity and inbreeding depression. Incorporating genetic data into the design of captive-release and translocation projects would refine management plans for this locally important population and monitor risks to its long-term survival.