Low genetic polymorphism and no population genetic structure detected during the natural recolonization of a large carnivore to its previous range

Abstract In the face of ongoing habitat loss and fragmentation, examining the genetic effects of range expansion can provide insight into the resilience and adaptability of large carnivore populations returning to parts of their former range. This study investigates the genetic structure of the Eurasian lynx ( Lynx lynx ) population during its natural range expansion into southern Sweden, an area from which it had been extirpated for over a century. We utilized genomic data from 600 individual lynx collected throughout the recolonization period to assess heterozygosity, inbreeding, and genetic differentiation. Our results indicate no significant genetic structure or barriers to gene flow during this recolonization event, despite potential physical barriers such as lakes, farmland, and human infrastructure. Observed and expected heterozygosity, as well as the inbreeding coefficient did not show significant variation over time or across latitude, suggesting that connectivity with the source population was maintained. Spatial principal component analysis, cluster analysis, and discriminant analysis of principal components further supported these findings, showing little spatial or temporal structure. This lack of genetic structure contrasts with the experience of smaller and more isolated lynx populations, which have become inbred. Our study, thus, provides valuable insights into the natural range expansion of a large carnivore in human-dominated landscapes and underscores the importance of ensuring genetic connectivity for successful recolonization and conservation efforts.