Data from: Admixture between released and wild game birds: a changing genetic landscape in European mallards (Anas platyrhynchos)

Disruption of naturally evolved spatial patterns of genetic variation and
local adaptations is a growing concern in wildlife management and
conservation. During the last decade, releases of native taxa with
potentially non-native genotypes have received increased attention. This
has mostly concerned conservation programs, but releases are also widely
carried out to boost harvest opportunities. The mallard, Anas
platyrhynchos, is one of few terrestrial migratory vertebrates subjected
to large-scale releases for hunting purposes. It is the most numerous and
widespread duck in the world, yet each year more than three million farmed
mallard ducklings are released into the wild in the European Union alone
to increase the harvestable population. This study aimed to determine the
genetic effects of such large-scale releases of a native species,
specifically if wild and released farmed mallards differ genetically among
subpopulations in Europe, if there are signs of admixture between the two
groups, if the genetic structure of the wild mallard population has
changed since large-scale releases began in the 1970s, and if the current
data matches global patterns across the Northern hemisphere. We used
Bayesian clustering (Structure software) and Discriminant Analysis of
Principal Components (DAPC) to analyze the genetic structure of historical
and present-day wild (n = 171 and n = 209, respectively) as well as farmed
(n = 211) mallards from six European countries as inferred by 360
single-nucleotide polymorphisms (SNPs). Both methods showed a clear
genetic differentiation between wild and farmed mallards. Admixed
individuals were found in the present-day wild population, implicating
introgression of farmed genotypes into wild mallards despite low survival
among released farmed mallards. Such cryptic introgression would alter the
genetic composition of wild populations and may have unknown long-term
consequences for conservation.