One wolf wonder

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One of the key problems facing the management of endangered species is the possibility that dwindling populations become isolated and inbred, further threatening their existence. There can be few species that have had a tougher recent time of it than the grey wolf (Canis lupus) which has been subject of intense hunting and extermination since the nineteenth century. In the 1960s the grey wolf was finally considered extinct on the Scandinavian peninsular. But 20 years ago, a small breeding pack was discovered in southern Scandinavia, more than 900 kilometres from the nearest known populations in Finland and Russia to the east, sparking controversy as to their origin. Preliminary studies revealed a lack of genetic variability in the fewer than 10 individuals comprising the pack during the 1980s. But after 1991, with no changes in their circumstances and continuing legal and illegal hunting, the population began to grow exponentially to a current position of 10–11 breeding packs comprising a total population of around 90–100. Intrigued by these findings, a team led by Carles Vila, at the University of Uppsala, and colleagues in Finland, Italy, Sweden and Norway, began a detailed genetic study of the expanding population. Using a variety of molecular tools, including maternally, paternally and bi-parentally inherited markers, the researchers began to track the population's origins. Lack of genetic variation in the group led the researchers to believe that a single pair of wolves originally founded it. The analyses also suggested that the pair were more closely related to the current eastern populations than the historical Scandinavian types. But after 1991, the researchers found a sudden increase in genetic variability in subsequently tested wolves. As they report in the Proceedings of the Royal Society, London Series B (published online), they concluded that a single male immigrant that had mated within the group had led to a boost in genetic diversity and mating success. Only immigrants that successfully reproduce within the population can contribute to the rescue of the population. The researchers found evidence of another immigrant wolf in Scandinavia in the early 1980s but it failed to reproduce and so did not contribute to the genetic make-up of the population. Such a dramatic improvement in genetic variability and viability, when an outsider breeds within a bottlenecked population, will be a cheering result for other conservationists and population biologists concerned about the genetic health of isolated and inbred populations: in this case at least, just a single outsider can make all the difference.