The meaning of wild: Genetic and adaptive consequences from large-scale releases of domestic mallards

The translocation of individuals around the world is leading to rising incidences of anthropogenic hybridization, particularly between domestic and wild congeners. We apply a landscape genomics approach for thousands of mallard (Anas platyrhynchos) samples across continental and island populations to determine the result of over a century of supplementation practices. We establish that a single domestic game-farm mallard breed is the source for contemporary release programs in Eurasia and North America, as well as for established feral populations in New Zealand and Hawaii. In particular, we identify central Europe and eastern North America as epicenters of ongoing anthropogenic hybridization, and conclude that the release of game-farm mallards continues to affect the genetic integrity of wild mallards. Conversely, self-sustaining feral populations in New Zealand and Hawaii not only show strong differentiation from their original stock, but also signatures of local adaptation occurring in less than a half-century since game-farm mallard releases have ceased. We conclude that 'wild' is not singular, and that even feral populations are capable of responding to natural processes. Although considered paradoxical to biological conservation, understanding the capacity for wildness among feral and feral admixed populations in human landscapes is critical as such interactions increase in the Anthropocene. A genomic investigation focusing on introgressive hybridization due to anthropogenic causes in mallards reveals a single domestic game-farm breed as the source for contemporary release programs in Eurasia and North America as well as for established feral populations in New Zealand and Hawaii.

Automated summary

A genomic investigation reveals that a single domestic game-farm breed of mallards is responsible for contemporary release programs in Eurasia and North America and established feral populations in New Zealand and Hawaii. Central Europe and eastern North America are identified as epicenters of ongoing hybridization, indicating that the genetic integrity of wild mallards is being affected. Self-sustaining feral populations in New Zealand and Hawaii show differentiation from their original stock and signs of local adaptation. Understanding the capacity for wildness among feral and feral admixed populations in human landscapes is crucial in the Anthropocene.