Genetic changes during the farming of wild mallards and the introgression of altered genotypes into the wild population
Deliberate release of species in nature is a common procedure to increase threatened populations, or to increase harvested populations. The practice of augmenting an already viable population for harvest reasons is frequently used within forestry, fisheries, and wildlife. Not until recently, the potential risks with these releases of native species have received deserved attention. Introgression of genetically distant individuals, e.g. closely related species, or released farmed conspecifics, with potential alien genes, may risk to break down local adaptions and decrease the genetic diversity. The mallard Anas platyrhynchos is the most widespread duck in the world and an important game species with an estimated annual harvest of about 4.5 million ducks in both Europe and North America. Large scale release of farmed mallards has since the 1970s become a common practice in Europe each year to increase the population for the following hunting season. Each year, three million unfledged hatchlings are released around Europe for hunting purposes. These released mallards look very similar to their wild counterparts on first sight, but exhibit significant differences: lower survival, shorter migration, lower lamellar density in their bills (important for semi-aquatic feeding). It is unknown to what extent the genetic integrity of farmed mallards still resembles the wild pool.
In this study we test if historical wild mallards (museum collections from before the times of wide-spread release), modern wild mallards and farmed mallards in France, Sweden and Czech Republic can be genetically separated from each other by using a set of single nucleotide polymorphism (SNP) markers. Our aim is also to see if wild individuals from around Europe already show signs of introgression from escaped farm mallards that threaten the native gene pools of the wild ducks.