Kulikova I.V., Shedko S.V.
Вавиловский журнал генетики и селекции 2026; 30(7): 1108-1118
The Mallard (Anas platyrhynchos Linnaeus, 1758) is a well-known dabbling duck, the most numerous and widely distributed in the world. Despite being a thoroughly studied species in all aspects of its biology, ecology, behavior, and genetics, the Mallard population structure in the Holarctic remains a complicated issue. We used 2,529 polymorphic loci obtained via double-digest restriction-site associated DNA sequencing (ddRAD-seq) to reexamine the genetic differentiation between populations of the Mallard and one of its close relatives in Eastern Asia, the Eastern Spot-billed Duck (Anas zonorhyncha Swinhoe, 1866). Comprehensive sampling allowed us to select only pure wild mallards for our research, resulting in a final dataset of ddRAD-seq profiles from 821 mallards and 23 Eastern spot-billed ducks. Population structure analysis confirmed weak genetic structure between wild mallards from Eurasia and North America attributable to small frequency differences across autosomal loci as well as the strong structuring of Greenland mallards. The differentiation of the Greenland Mallard (A. p. conboschas) from the nominate subspecies (A. p. platyrhynchos) was higher than the differentiation between the Mallard (A. p. platyrhynchos) and the Eastern Spot-billed Duck (A. zonorhyncha) based on both autosomal and Z-linked loci. The Eastern Spot-billed Duck was found to be more closely related to mallards from Eurasia than to mallards from North America at autosomal loci but differed from both groups at Z-linked loci. Our findings are compatible with three evolutionary scenarios: (i) incipient neutral divergence between Eurasian and North American mallards, (ii) divergence-with-gene-flow potentially supported by sex-linked barriers between Mallard and Eastern Spot-billed Duck, and (iii) divergence associated with founder effects and local adaptation in the Greenland Mallard.
