Establishing a genetic system to distinguish between domestic Mallards, Pacific Black Ducks and their hybrids

Dabbling ducks are subject to many threatening processes. Hybridisation with introduced Mallards (Anas platyrhynchos) is a threat that is commonly overlooked. Mallards, both domestic and wild, have been introduced in Australia and New Zealand. While hybridisation with Mallards caused significant decline in the New Zealand populations of Pacific Black (Grey) Ducks (Anas superciliosa), the degree of hybridisation between Mallard and the Pacific Black Duck in Australia is currently unknown, largely because hybrid backcrosses are difficult to visually identify. We screened 27 cross-amplifying waterfowl microsatellite markers and developed a set of 9 markers that can be used for genotyping and assignment tests to identify cryptic hybrids. Assignment tests, performed with the program Structure 2.3.4, had a 99 % likelihood that specimens of a known species (Mallard or Pacific Black Duck) were assigned to the correct group. The system was applied used to confirm the hybrid status of two putative hybrids identified phenotypically. The successful application of this system demonstrates its potential use in determining the rate of hybridisation between introduced Mallards and Pacific Black Ducks throughout Australia.