The effect of a rabbit haemorrhagic disease epidemic on the temporal and spatial structure of an invasive rabbit population

Abstract The European rabbit ( Oryctolagus cuniculus ) has been a remarkably successful invasive species due to its generalist nature and fast reproduction. The rabbit population in Helsinki (Finland) originated from escaped pet rabbits in the late 1980s, and the population expanded rapidly in the early 2000s. The Rabbit haemorrhagic disease (RHD) spread naturally to Finland in 2016, and the disease caused a significant reduction in the Helsinki area population. The aim of this study was to examine the effect of the RHD epidemic on genetic diversity, and on the temporal and spatial population structure of the Helsinki area rabbit population from samples collected before and after the epidemic. We found that genetic diversity in the Helsinki area rabbits is low compared to other wild rabbit populations worldwide. An initial founding effect could be detected in the population, but the effect of the RHD epidemic on genetic diversity was unclear, and there was no obvious bottleneck after it. Interestingly, genetic diversity was higher after the population crash, which may be explained by continuing gene flow from escaped and/or intentionally released pet rabbits. Although the period of separation has been relatively short, the subpopulations have already diverged genetically to some extent, indicating that dispersal is not unrestricted across the study area. There was also a slight allele frequency shift after the RHD epidemic. The European rabbit has become an established member of the Finnish fauna, and eliminating this invasive species would be difficult, as the current population is continually replenished by escaping and intentionally released pet rabbits.