Polar bears can genetically adjust to warming, study shows

A study published in the journal Mobile DNA has found that genes related to heat stress, aging and metabolism work differently in bears living in southeast Greenland.

The authors note that these genetic shifts may play an important role in how different polar bear populations adapt (or evolutionarily change) in response to localised changes in climate and diet. Understanding such processes, they say, is important for the conservation of the species - it helps assess which populations are most vulnerable and which have the best chance of surviving in a warming environment.

The context remains alarming: it is predicted that more than two-thirds of polar bears could disappear by 2050, and by the end of the century the species is at risk of becoming completely extinct. The Arctic Ocean is now experiencing the highest temperatures on record; sea ice is shrinking, depriving bears of seal hunting grounds, leading to isolated populations and food shortages.

How the study was conducted

The team analysed blood samples from polar bears from northeast and southeast Greenland, comparing the activity of so-called "jumping genes" (transposons) - mobile parts of the genome that can affect the function of other genes. The scientists compared this activity with temperature conditions in the two regions and changes in gene expression.

It turned out that the north-east of Greenland is colder and more stable, while in the south-east the climate is noticeably warmer, with less ice and more pronounced temperature fluctuations. The conditions in this area are similar to scenarios predicted for polar bears in the future.

Study lead author Dr Alice Godden (UEA) emphasises: the results offer "some hope" but do not negate the need to curb rising global temperatures.

Comparing genetic activity with climate data, she says: warming appears to be linked to a sharp increase in transposon activity in bears in south-east Greenland. This means that different sections of DNA can change at different rates in different groups of bears - and this process is probably tied to specific habitats.

What this could mean for survival

The researchers believe this is one of the first papers to obtain a statistically significant link between rising temperatures and DNA changes in a wild mammal. They also found changes in areas associated with fat processing, which is important when food is scarce. The authors suggest that southeastern bears may be gradually adjusting to a more "hardy" diet, which in warmer areas may include more plant sources compared to the traditional "fatty" seal diet of northern populations.

The team also described "genetic hotspots" where transposons are particularly active; some of these sites are located in protein-coding regions, which may indicate a more profound rearrangement of the genome in response to the disappearance of sea ice.

What's next

The work builds on previous findings that the polar bear population of southeast Greenland is genetically distinct from that of northeast Greenland and likely became isolated about 200 years ago. They included data from 17 adults (12 from the northeast and five from the southeast) in the analysis and used RNA sequencing to assess which genes are active.

The next step, according to the authors, is to see if a similar mechanism is observed in other populations (about 20 worldwide) and to study polar bear genomes in detail while this is still possible.