The effects of climate change on Arctic habitat may have induced adaptation to global warming in the DNA of humans polar bears. A recent study conducted by University of East Anglia and published on Mobile DNA investigated the effects genetics caused by ecological variations – in particular the increase in temperature and consequently the availability of food or the loss of sea ice – right on the polar bears (Ursus maritimus) who live in different areas of Greenland. According to this study, some DNA sequences capable of moving within the genome, known as transposable elements (transposable elements, TEs), would be more active in bears living in areas with higher temperatures, indicating a possible adaptation effect of polar bears to a changing climate and an increasingly warmer environment that has less and less ice and resources.
A bear that “rewrites” its own DNA
The term “jumping gene” describes a well-known biological phenomenon, namely the ability of some DNA sequences Of move within the genome (hence the incorrect journalistic definition of “jumping genes”), becoming transposable elements (TEs). These elements do not contain information (encode) useful proteins per se, but they can alter the activity of other genes by inserting themselves near them or modifying their adjustment. In some stressful ecological circumstances, this increased mobility can provide genetic raw material on which natural selection can act. This is the case of polar bears (Ursus maritimus)of which the study analyzes the genetic effects caused by ecological variations, in particular by analyzing the differences in TEs in bears living in various areas of Greenland and on which the increase in temperatures has induced different alterations.
Researchers at the University of East Anglia analyzed the genome of 17 bears belonging to two distinct regions of Greenlandthe area of South East (SEG) and that of North East (NEG) which differ in their environmental conditions: in particular the southern Arctic region has been experiencing this for some time now higher and more variable temperatures compared to the North.
Southern bears are more at risk than northern ones
Following genetic analyses and comparisons, scientists observed quantifiable differences in gene expression between the two groups, linked to metabolic pathways, responses to heat stress and aging processes, suggesting that those in the south seem more resilient to climate change. In particular, one was found increased activity of transposable elements (TEs) in the genome of southern individuals compared to the northern population, in a statistically significant manner and linked to the increase in temperatures.
Changes were also recorded in areas of the genome linked to fat metabolisation, which may be relevant given that the bear’s diet varies with the presence of rich and persistent ice: populations living in environments with little ice may have more variable and less fat-rich diets than typical bears of high latitudes. All data that makes us assume that the bears attempted a survival strategy to live with new climates and what comes from them.
It is important to emphasize that these variations are not “random mutations” in the classical sense, but rather changes in the activity of genetic elements already present in the genome. In other words, the bears aren’t developing entirely new genes, they’re rather reusing portions of their DNA in different wayspotentially to respond to new environmental stresses. If we look at the bigger picture, the idea is not that polar bears will get rid of the problem of climate change thanks to new mutations, but how they can respond resiliently to a changing environment faster than many other species.
What will the consequences be for bears in the future?
Although these discoveries are fascinating and open new perspectives on adaptive biologyit must be kept in mind that not all polar bear populations show these same genetic signals and that the evidence specifically concerns only the population originating from the South-East of Greenland. It’s not clear then if, how and to what extent the activity of the transposable elements can guarantee greater survivalnor whether these genetic changes translate into concrete ecological advantages.
Not to mention the fact that the problem of anyway climate change That remains a very serious threat: although some populations show signs of genetic plasticitythe loss of sea ice, rising temperatures and altered diets risk exceeding the natural adaptive capacity of many others. It is likely that some variations in genes can affect the ability to regulate physiological processes as thermal stress varies, but this remains to be seen. If it were truly possible to understand the role of TEs in reshaping genetic networks favoring survival in warmer climates, it could improve awareness, conservation strategies and targeted management of many at-risk species.
