Restoration of an inbred adder population

The negative effects of inbreeding on population size are well documented in captive animals, but there is surprisingly little evidence that genetic factors cause a decline in wild populations, apart from a reported correlation of low levels of genetic variability with a high incidence of malformed or stillborn offspring. 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.