How do Rattus norvegicus disperse in rural landscapes? Insights from population genomics on livestock farms

Rattus norvegicus is a global pest in rural landscapes, yet little is known about its dispersal in these environments. We addressed this issue using RAD-seq markers for 93 individuals from 16 farms along two perpendicular transects, one by a river and the other by a road, in a 561,736-hectare rural landscape in central Argentina. A matrix of 764 SNPs was generated for population genetics and kinship analyses. No clear population structure emerged, suggesting high gene flow. However, farms from neighboring localities showed a tendency to cluster in the neighbor-joining tree. We detected isolation by distance along the road but not the river, and found half and full siblings over 30 km apart in both transects, suggesting active and passive dispersal by human transport. The road appears to function as a corridor across generations, linked to IBD, while no such pattern was found along the river. Nevertheless, we identified a few relatives over long distances along the river, suggesting that watercourses may facilitate dispersal, at least within a single generation. These findings help explain the challenge of controlling R. norvegicus on farms where control measures are often implemented individually by farmers.