Study: Alpine marmots are genetically very similar
A research team has decoded the genome of the Alpine marmot. The rodents reportedly show the lowest genetic diversity of all wild mammals sequenced to date.
The fact that the genetic makeup of individual animals is so similar came as a surprise to scientists, “since genetic impoverishment is found primarily in highly endangered species, such as the mountain gorilla,” explained biologist Markus Ralser, head of the Institute of Biochemistry at the Charité in Berlin. Yet Alpine marmots are not considered endangered — hundreds of thousands of them live above the tree line in the mountains.
In search of an explanation for the low genetic diversity, the researchers reconstructed the animals’ genetic past by analysing the genome as well as fossils. They report their findings in the journal «Current Biology».
Repeated adaptation
Their conclusion: the Alpine marmot lost its genetic diversity because it had to adapt multiple times to the climate changes of the last major ice age — first when it colonised the ice-age steppe around 110’000 years ago, and again when that habitat disappeared towards the end of the ice age approximately 10’000 to 15’000 years ago. Since then, the animals have lived in the higher-altitude steppe of the high Alps, where temperatures resemble those of the ice-age steppe.
During the analysis, the scientists found evidence that adaptation to the colder temperatures of the ice-age steppe led to a slowing of the marmots’ generation time and a reduction in their mutation rate. The rodents’ genome shows an exceptionally slow rate of evolution, which is why the animals were unable to build up significant new genetic diversity after the end of the ice age.
Greater vulnerability
This is why Ralser finds it “remarkable that the Alpine marmot has managed to survive for thousands of years despite its genetic poverty.» Because low genetic diversity means greater susceptibility to diseases, for example, and reduced adaptability to environmental changes such as climate change.
The fact that climate change can have such long-term effects on the genetic diversity of a species had not previously been known with such clarity. Since low genetic diversity poses a risk of extinction, the researchers consider it important to study other animal species that survived the Ice Age more closely as well. Because these could find themselves in a similarly genetically impoverished situation. «At the moment, the endangerment of a species is usually assessed solely by the number of animals capable of reproducing. We should reconsider using this as the only criterion», explained Ralser.
