Matings between relatives have negative consequences for the offspring, a phenomenon known as inbreeding depression. But what if you end up with a related partner? Initiated by a scientist at the Max Planck Research Centre for Ornithology, a study by an international team of scientists showed that social mates that are genetically similar use alternative reproductive behaviors to avoid paying the price of inbreeding. Combining field observations on free-living populations of three shorebirds with molecular methods to determine parentage and relatedness between the partners they found that extra-pair parentage occurred when mates were more closely related (Nature, Oct. 10th, 2002).

Over the past decade, the use of molecular techniques to determine parentage has led to the realization that monogamy is rare in nature. Although most bird species are socially monogamous, broods often contain young that are not related to one of the parents tending the nest. This can be the result of two alternative reproductive behaviors. Extra-pair paternity occurs when females copulate with males other than their social partner, and these copulations lead to fertilizations. Extra-pair paternity is common in songbirds, but much less common in other birds. Quasi-parasitism occurs when a male copulates with another female, who then lays one or more eggs that he fathered in his nest. This is a rare and little understood phenomenon. The reasons why birds are unfaithful to their social partner, with whom they raise the offspring, has been the focus of much debate. A scientist at the Max Planck Research Centre for Ornithology initiated a study on parentage in shorebirds, and in collaboration with researchers at the Konrad Lorenz Institute for Comparative Ethology in Vienna, combined data on three species from three continents. An international team of scientists studied populations of marked individuals in the field and closely monitored their breeding behavior. Based on blood samples
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Contact: Dr Bart Kempenaers
b.kempenaers@erl.ornithol.mpg.de
49-8157-932334
Max-Planck-Gesellschaft
10-Oct-2002

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