Worryingly low levels of genetic diversity make Scotland’s red squirrels especially vulnerable to disease, a study has shown.
Researchers at the University of Edinburgh said this could explain why the mammals are so slow to develop resistance to the squirrelpox virus, which is carried by non-native grey squirrels and fatal to reds.
The study saw researchers analyse the entire genetic code of 106 red squirrels from across Scotland and Formby in north-west England.
They found the species had lower levels of genetic diversity than some of the world’s most endangered animals, including the Iberian lynx and the Amur tiger.
Genetic diversity is important for species’ survival as it helps them adapt to environmental changes, as well as making them more resilient to threats like disease and habitat loss.
Researchers pointed out that the squirrels’ movement across Scotland is restricted by natural and man-made barriers, including the Cairngorm mountains in the north and cities in the central belt.
This has resulted, they said, in squirrels living in pockets of isolated populations, with the north east of Scotland being one of the only areas the animals can move freely from north to south.
Red squirrels are endangered in the UK and considered a conservation priority in Scotland, a key stronghold for the animals.
Study lead Dr Melissa Marr, from the University of Edinburgh, said the study was the first to use “whole genomes” to study Scotland’s 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,” she said.
“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.”
The researchers said continued genetic monitoring and interventions are urgently needed to improve the species’ diversity and boost conservation efforts.
They suggested “translocating” squirrels between populations could be one way of introducing more genetic diversity.
Samples for the study were sourced from the red squirrel disease surveillance programme at the University of Edinburgh’s Royal (Dick) School of Veterinary Studies, which has been analysing red squirrel mortality across Scotland for 20 years.
The study team also included scientists from Forestry and Land Scotland (FLS) and National Museums Scotland (NMS), which provided additional samples for the study.
Dr Andrew Kitchener, senior curator of vertebrate biology at NMS, described the important role the museum’s collections played in the research.
“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 NMS, 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.”
The study, which is published in the journal Evolutionary Applications, was funded by UKRI-NERC and the University of Edinburgh, FLS and CryoArks.
