Genetic distinctiveness of the Waikawa Island mouse population indicates low rate of dispersal from mainland New Zealand

In New Zealand, mice in reserves can complicate the control of mammalian predator invasion by masking scent and eating baits. Eradicating mice allows predator invasions to be more readily detected and managed, but removal of mice is only feasible if recolonisation is rare. We used genetics and morphology to assess whether the mouse population on Waikawa Island was isolated from the mainland population. A sample of mitochondrial DNA sequences revealed that at least four female mice must have founded the Waikawa population, but that gene flow between island and mainland mice is limited. Although no variation in DNA sequences of exon 1 of the nuclear gene vitamin K 2,3-epoxide reductase subcomponent 1 was detected, the common allele is not associated with resistance to anticoagulant rodenticides such as warfarin. Body size comparisons revealed the island population as distinct, possibly due to age structure differences. We infer low levels of successful dispersal between the mainland and Waikawa Island mouse populations and suggest eradication might be sustainable in the long-term if protection against rodent invasion is maintained.