Mitochondrial Genetic Diversity of Eurasian Red Squirrels (Sciurus vulgaris) from Denmark

Melanistic Eurasian red squirrels Sciurus vulgaris are commonly found on the Danish island of Funen. They are thought to represent native Danish squirrel types and are presently under threat from admixture with introduced red squirrels. In response, a conservation program was started in 2009 that involves the translocation of melanistic squirrels from Funen to the squirrel-free island of Langeland. Using mitochondrial DNA of 101 historical and modern samples from throughout Denmark, we assess for the first time population structure and mitochondrial genetic diversity of Danish squirrels compared to its larger pan-Eurasian distribution. We find that Danish squirrels have low levels of genetic diversity, especially melanistic individuals. Bayesian skyline reconstructions show that Danish squirrels have most probably experienced a severe bottleneck within the last 200 years. Also, fine-scale genetic structure was found between squirrels from the regions of Funen, Zealand and Jutland, which mimics the insular geography of Denmark. Additional nuclear DNA analyses will be required to determine the precise admixture levels between original Danish and introduced squirrels and to locate unmixed candidate populations for specific conservation efforts.