The Arctic will not be essentially the most hospitable place on Earth. Some Arctic animals like reindeer have a number of genetic variations to assist them thrive there, and one of many area’s high predators is not any exception. Scientists are piecing collectively when polar bears (Ursus maritimus) might have advanced a few of the genes that separate them from brown bears (Ursus arctos). New genomic evaluation reveals that they might have modified as just lately as 70,000 years in the past. The findings are detailed in a study published September 15 in the journal BMC Genomics.
Polar bears are very carefully associated to brown bears, however have quite a few key variations that assist them survive in excessive arctic situations. They have two layers of fur to assist them preserve heat and dry. The primary is a big downy layer that’s situated proper subsequent to their pores and skin. The opposite layer is product of longer hairs known as guard hairs that act like a raincoat. Their fur’s signature bright white hue helps them camouflage. Polar bears also can digest excessive quantities of ldl cholesterol from blubber without damaging their hearts. This helps them thrive whereas consuming seals and even some whale species like belugas.
[Related: Jackrabbit’s color-changing fur may prepare them for climate change.]
Scientists imagine that the polar bears and brown bears diverged pretty just lately in evolutionary phrases–inside roughly the previous a million years. Simply how and when polar bears tailored to the Arctic remains to be debated.
On this study, a workforce analyzed the genomes of 119 fashionable polar bears, 135 fashionable brown bears, and two fossilized polar bears. One of many fossils was the Poolepynten jawbone from the Norwegian archipelago of Svalbard that dates again between 130,000 and 100,000 years in the past. The opposite fossil was a juvenile polar bear skull nicknamed Bruno that was present in Alaska’s Beaufort Sea. Regardless of the title, Bruno was a female bear that lived someplace between 100,000 and 70,000 years in the past and its genome has helped scientists slender in on this brown bear-polar bear divergence.
“We discovered some variants which will have been chosen within the final ~70,000 years (i.e. they weren’t within the fossil polar bears),” research co-author and College of Copenhagen evolutionary biologist Michael Westbury tells In style Science. “It was at all times assumed that when polar bears diverged from brown bears, they should have rapidly tailored to the Arctic in a single speedy evolutionary change. Nonetheless, our outcomes recommend which will haven’t been the case, and the variation to the Arctic was a extra gradual course of.”
The workforce in contrast these genomes to find out when seven key genes for Arctic variations had been chosen. They discovered that for four of the genes (ABCC6, AIM1, COL5A3, and POLR1A), the entire polar bear genomes had the identical DNA variant current. That is known as a fixed allele, which is the one variant current for a selected gene inside a inhabitants.
Nonetheless, the brown bear genomes had a number of alleles. This implies that these genes had already been chosen for in some historic polar bear ancestor, and polar bears had variations for Arctic life earlier of their evolution.
Nonetheless, three of the genes–known as APOB, LYST, and TTN–contained alleles that have been fixed in the modern polar bear genomes, but not in the ancient ones. APOB, LYST, and TTN genes are associated to cardiovascular features. APOB and TTN are associated to metabolism. APOB and LYST are associated to pigmentation.
[Related: What an ancient jawbone reveals about polar bear evolution.]
The workforce believes that these genes may be associated with the variations that turned essential for polar bears to outlive in newer historical past, maybe in the direction of the top of the final ice age. Additionally it is unclear if different arctic animals have related variations on these genes that have an effect on their fur shade, coronary heart well being, and metabolism.
“I assume copies of those genes are present in most animals, however it could be the particular variants within the polar bear that allowed them to stay within the Arctic,” says Westbury. “We didn’t look into whether or not another Arctic animals had the identical variants, however that might be fascinating for a comply with up research.”
