The full-genome sequencing of 97 Scandinavian wolves has revealed the true extent of their inbreeding, which is a considerable long-term threat to the population.
Inbreeding occurs in small populations when closely-related individuals mate. It is a well-documented issue for the Scandinavian wolves as the population was founded in the 1980s by only two individuals.
New research has now revealed a detailed analysis of inbreeding in these animals.
“Inbreeding has been so extensive that some individuals have entire chromosomes that completely lack genetic variation,” says Prof Hans Ellegren from Uppsala University. “In such cases identical chromosome copies have been inherited from both parents”.
Offspring inherit two of each chromosome, one from their mother and one from their father, producing a new and unique combination of genes.
However, many of the wolves were found to have chromosome pairs that were very similar or even identical, indicating severe inbreeding.
The most surprising finding was the high level of inbreeding and relatedness in immigrant wolves. This was observed when two wolves were translocated from Northern to Southern Sweden to reduce conflict with farmed reindeer.
Introducing individuals from different areas usually increases genetic variation in a population, however these wolves were found to be far more closely related to their new neighbours than expected.
Wolves were declared to be extinct in the wild in Scandinavia in the 1960s but successfully recolonised the area 20 years later.
The mammals benefited from the introduction of a law making it illegal for them to be shot and there are now estimated to be around 46 family groups across Scandinavia.
Main image: Wolves in Scandanavia are more closely related than previously thought. © Roger Eritja/Getty