A study finds that American black bears evolve to have cinnamon-colored coats
Some American black bears in the western United States have it evolved To have cinnamon-colored fur. A new study finds that the new coloration is likely due to a genetic variant similar to the one that causes albinism in humans.
It was analyzed by researchers from the United States and Japan DNA samples from 151 American black bears (bear) across the United States and Canada and found that those residing in western states like Nevada, Arizona and Idaho were more likely to show red-colored coats than the black fur for which medium-sized bears are named.
Researchers have identified a mutation known as R153C in a gene called associated tyrosinase protein 1 (TYRP1), which causes a change in coat color that makes its fur the same color as a copper penny.
“TYRP1 is a known pigmentation gene in the pathway in precursor molecules that eventually produces either eumelanin (a black or brown pigment) or pheomelanin (a red or yellow pigment),” Emily Bucket (Opens in a new tab), lead author of the study and assistant professor of biological sciences at the University of Memphis in Tennessee, told Live Science. “What it does is change the amino acid sequence of that gene.”
This “cinnamon variant,” which Puckett calls a “young boom,” came about about 9,360 years ago, according to the study, and gradually spread through the population.
Related: Scientists extracted ancient DNA from a 32,000-year-old bear skull
Black bears elsewhere in the United States, including along the Great Lakes and in the Northeast, are unlikely to show red fur because this small mutation “hasn’t had enough time for a natural migration,” Buckett said.
“Geography definitely plays a role,” she said. “Our demographic modeling determined that the most likely place for the mutation to emerge was somewhere in the western region, very likely in the southwest. From there, it expanded through gene flow through the population.”
But even this is a slow process, as the majority of black bears on the East Coast still wear jet-black fur.
“The bears don’t pass through the Great Plains,” Buckett said. “If they wanted to go east, they would have to go up north into Canada, through Canada [Prairies], around the Great Lakes region and then descend again to the eastern populations. That will take a long time. We see it happening and moving [eastward]But it’s a process that takes time.”
The researchers also examined whether the development of this gene in western American black bears has something to do with thermoregulation, a mechanism that helps mammals regulate their bodies. Temperaturesor compete with another species of cinnamon bear: brown bears (Ursus arctos), also known as grizzly bears.
Our models indicate that yes, [the gene is] Adapt in some way, but we’re not 100 percent sure what you’re adapting to,” Paquette said. We have tested both thermoregulation and competition with brown bears, and neither is strongly supported. Our new hypothesis is that it is a mechanism for selective advantage.”
Interestingly, the variant is similar to that in humans known as oculocutaneous albinism type 3 (OCA3) which causes lighter hair color and skintwo distinctive features albinism. In some cases, it can also lead to visual impairment.
“Surprisingly, the bears do not show signs of visual problems, as it would be difficult for them to survive,” Paquette said.
The results are published Dec. 16 in the journal Nature Current Biology (Opens in a new tab).
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