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Crossbreeding with domestic ducks, a major threat to native ducks?

The genetic merging comes about because the hybrid offspring of Mallards and Pacific Black Ducks are fertile, and their mixed genes pass down to future generations and gradually merge to create a distinct gene pool – this process is called introgression.

Dr Patrick Guay, from the University's Institute of Sustainability and Innovation and School of Engineering and Science, has found that it is already too late for many duck populations across the globe, which have been made locally extinct, or nearly extinct, due to hybridisation with both wild and domesticated Mallards.

Dr Guay is now in the middle of a three year project to determine the threat that Mallards pose in Australia.   He is working with Dr. Randall Robinson from the School of Engineering and Science and PhD student Alice Taysom to perform a painstaking census of as many Black and Mallard ducks as possible to determine the current extent of hybridisation.

"What we do is capture a live duck and take a little blood sample," says Guay. "If it's dead we can take a tissue sample. We can get all the data we want if we get some blood or a feather." The DNA analysis determines what percentage comes from its purebred ancestors. A first generation hybrid duck would yield a DNA result of 50/50; half of the DNA is of Pacific Black Duck origin, and half is of Mallard origin.

If the research proves that Black Ducks are disappearing, what are the implications?  The loss of just one species from an ecosystem can have enormous consequences. Healthy ecosystems rely on a state of harmony between resident species, which all depend on one another in some way. As an example, Guay says it could be that the Black Duck is eating an insect that would otherwise be a plague on an important native plant. The loss of the Pacific Black Duck from Australia is not inevitable. The solution will require a concerted effort on the part of both government and duck owners. "The solution is to segregate domestic ducks from wild ducks," says Guay. "People shouldn't release their pet ducks into the wild, and it's important not to feed ducks in an urban setting. If we properly chaperone the Mallards, it is much harder for them to make those unwelcome advances."

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