Scotland’s red squirrels have among the lowest genetic diversity of any species, leaving them vulnerable to disease outbreaks, a study shows.
Red squirrels’ lack of diversity could explain why they are slow to develop resistance to the squirrelpox virus, which is carried by non-native grey squirrels and fatal to reds, scientists say.
Continued genetic monitoring and interventions are urgently needed to improve red squirrel diversity and boost conservation efforts, experts warn.
Vulnerable population
Genetic diversity is important for species' survival, scientists say. It helps populations adapt to environmental changes and makes them more resilient to threats such as diseases and habitat loss.
Red squirrels are endangered in the UK and considered a conservation priority in Scotland, a key stronghold for the animals.
Scientists from the University of Edinburgh analysed the entire genetic code of 106 red squirrels from across Scotland and Formby in north-west England, to better understand how closely related they are and track the spread of populations.
Researchers found that as a species red squirrels’ level of genetic diversity is lower than some of the world’s most endangered animals, including the Iberian lynx and Amur tiger.
This is the first-time whole genomes have been used to study Scottish red squirrels. Historical records show that they have faced many threats in the past, and this is clearly reflected in their DNA which shows worryingly low levels of diversity. By highlighting this low genetic diversity, and how their populations are spread over the landscape, our findings offer critical new information to help secure the future of this iconic native species for generations to come.
Dr Melissa Marr
Study lead from the Royal (Dick) School of Veterinary Studies
Restricted movement
Their movement across Scotland is restricted by natural and man-made barriers, such as the Cairngorm mountains in the north and cities in the Central Belt, creating pockets of isolated populations. The north east of Scotland remains one of the only areas where the animals are free to move between the north and south.
Translocation of squirrels – moving squirrels between populations – may be one option to enrich their diversity. The new study shows the role genetics can play by moving squirrels to locations to introduce greater genetic variety into populations, experts say.
Samples for the study were sourced from the red squirrel disease surveillance programme at the University’s Royal (Dick) School of Veterinary Studies, which has been analysing red squirrel mortality across Scotland for 20 years. National Museums Scotland provided additional samples.
The study team included scientists from National Museums Scotland and Forestry and Land Scotland. The research was funded by UKRI-NERC and the University of Edinburgh (facilitated by a Daphne Jackson Trust Fellowship), Forestry and Land Scotland and CryoArks.
Samples from red squirrels in our Natural Sciences collection from different populations in Britain covering the last 30 years have enabled this study to look at population changes over that time, and for any regional variation. This underlines the importance of collections like ours at National Museums Scotland, amassed over the long-term, which enables us to reflect changes in the environment over time. In addition to physical specimens, we have in recent years established a growing biobank of tissue samples, which are crucial in providing high quality DNA for whole genome studies such as this one.
Dr Andrew Kitchener
Senior Curator of Vertebrate Biology at National Museums Scotland
