GREG BARSH
The result of the Barsh lab studies on bears illustrate how genetic variation in melanin biosynthesis can underlie iconic phenotypes and inform a better understanding of color variation and recent evolution in large carnivores.
American Black Bear cub
within their environments. Here, the researchers suggest crypsis as a broader adaptive mechanism for large-bodied species. These results illustrate how genetic variation in melanin biosynthesis can underlie iconic phenotypes and
WHEN AND WHERE DID THE CINNAMON MORPH ARISE?
The TYRP1 R153C variant was primarily found in the south- west United States, at lower frequencies moving north- ward to Southeast Alaska and the Yukon Territory. TYRP1 R153C was associated with the cinnamon color in black bears and the chocolate and light brown colors, meaning it accounts for almost all of the color diversity among U. americanus . The researchers used their data to learn more about the TYRP1 R153C mutation. One idea is that it may have started in grizzly bears and was transferred to black bears, but demographic analysis indicated that was not the case. Instead, the TYRP1 R153C mutation arose spontaneously about 9,360 years ago in black bears living in the western United States, then spread as the bears moved across their current geographic range. The R153C variant that arose in black bears over 9,000 years ago must have provided an adaptive advantage to the bears based on its wide range today. The team used genet- ic modeling and simulations to predict the selective forces acting on the cinnamon morph. Their predictions ruled out two popular ideas: mimicry and thermoregulation. As to why the coat color variant arose in the first place, the team presents a new hypothesis: crypsis. Crypsis refers to the ability of an animal to conceal itself and blend into the environment. Generally, crypsis is found in prey species and ambush predators who color match
inform a better understanding of color variation and recent evolu- tion in large carnivores. ■
Greg Barsh, MD, PhD, is a faculty investiga- tor and Smith Family Chair in Genomics at the HudsonAlpha Institute for Biotechnology
RESEARCH REPORT
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