Genome sequencing reveals extensive inbreeding in Scandinavian wolves

The Scandinavian wolf population was founded in the 1980s by only two individuals. This has subsequently led to intense inbreeding, which is considered a long-term threat to the population. To reveal the genetic consequences of inbreeding, the whole genome of some 100 Scandinavian wolves has now been analysed.

'Inbreeding has been so extensive that some individuals have entire chromosomes that completely lack genetic variation', says Hans Ellegren, Professor at the Evolutionary Biology Centre, Uppsala University and leader of the study. 'In such cases identical chromosome copies have been inherited from both parents.'

A surprising discovery was that also some immigrant wolves were partly inbred, and related. This was the case, for example, for two wolves that 2013 were translocated by management authorities from northernmost Sweden, due to conflict with reindeer husbandry, to southern Sweden. This is counter to the often-made assumption of unrelated and non-inbred founders when inbreeding is estimated from pedigrees.

'The degree of inbreeding determined at high precision with genome analysis agreed rather well with inbreeding estimated from established pedigrees', says Hans Ellegren. 'However, for stochastic reasons, some wolves were found to be a bit more, and others a bit less, inbred than estimated from pedigrees.'

Moreover, wolves were generally more inbred than expected from recent mating between relatives in the contemporary population. This is because the two copies of a chromosome in an individual can originate from one and the same ancestor further back in time.

The study is a collaboration between Uppsala University, Swedish University of Agricultural Sciences, Inland Norway University, and Norwegian Institute for Nature Research.