Urban restoration of common species: population genetics of reintroduced native bush rats Rattus fuscipes in Sydney, Australia

Common species play a disproportionate role in shaping ecosystem structure and function, but are currently under‐represented in conservation translocation initiatives. This represents a missed opportunity because common species are typically easier to source for restoration projects, and larger numbers of common species can feasibly be translocated without substantially impacting source populations. Reintroduction of common species is an important first step in the faunal restoration of severely impacted habitats, such as urban spaces. Common species typically retain higher genetic diversity than threatened species, but this also means that they may have more to lose via population bottlenecks that can occur from translocation. To inform efforts to translocate common species, we assessed genetic impacts of a reintroduction of the common native bush rat Rattus fuscipes to an urban reserve at North Head, Sydney (Australia). Using single‐nucleotide polymorphism diversity, we found that differentiation between source populations was low. Nevertheless, admixture during reintroduction and follow‐up translocations initially increased standardized observed heterozygosity of North Head‐born bush rats and population NE, with a subtle corresponding decrease in within‐population kinship. For 3 years following the last translocation, we detected a small decline in genetic diversity in the North Head population, although final statistics remained similar to the source populations. Our results indicate that no short‐term interventions are necessary to further promote bush rat genetic diversity at North Head, but that continued genetic monitoring will be important to determine whether a trend in declining diversity continues as the population stabilizes. We conclude that translocation of a large number of individuals from multiple sources presents a suitable option for restoring an extirpated small mammal population whilst minimizing genetic effects typically associated with such management actions. Common species present viable candidates for translocations aiming to return biodiversity to disturbed or fragmented urban ecosystems. Native Australian bush rat Rattus fuscipes identified during a recent survey at North Head, Sydney. Using genomic analysis of the reintroduced bush rat population at the site, our study shows that translocations of common species can successfully maintain population genetic diversity, an important outcome as urban restoration improves ecosystem