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Conservation biology

Restoration of an inbred adder population


The negative effects of inbreeding on population size are well documented in captive animals1, but there is surprisingly little evidence that genetic factors cause a decline in wild populations2,3, apart from a reported correlation of low levels of genetic variability with a high incidence of malformed or stillborn offspring4. From the point of view of conservation strategies, it is not only the effect of genetic factors on population decline that needs to be considered, but also whether introducing novel genes can prevent or reverse such a decline. Here we show that the introduction of new genes into a severely inbred and isolated population of adders (Vipera berus) halted its precipitous decline towards extinction and expanded the population dramatically.

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Figure 1: Introducing new males increases the genetic diversity and enables the adder population to recover.


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Madsen, T., Shine, R., Olsson, M. et al. Restoration of an inbred adder population. Nature 402, 34–35 (1999).

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