Evolutionary ‘secret sauce’ found

The Canadian Press
Bob Weber

Research suggests hares and jackrabbits hopping along in the Rocky Mountains demonstrate the “secret sauce” for how animals can adapt to a new climate.
Scott Mills, lead author of a paper published recently in “Science,” says lessons from mixed populations of brown and white bunnies can be applied widely to help species adjust as the environment changes around them.
“We call it polymorphism but I also call it the ‘secret sauce’ for rapid evolution,” said Mills, a biologist at the University of Montana.
“The more variation that’s available for natural selection to act on, the faster it can act.”
Mills and his colleagues were interested in examining the consequences of climate change using animals’ coat colour.
There are 21 species that change colour from winter to summer and Mills’ paper looks at eight of them, including hares, jackrabbits, Arctic foxes, and weasels.
Species evolve to fit specific conditions. When those conditions change, there’s a mismatch.
If your coat is white when there’s no snow to blend in with, that’s a problem.
“White hares on a brown background get killed,” said Mills. “And the biggest signal of climate change is a reduction of number of days of snow on the ground.”
That reduction is happening faster than evolution.
Different populations within the same species also evolve differently to fit local conditions. Some hares and jackrabbits, mostly in northern areas, turn white in winter; some stay brown all year.
“Evolution will happen everywhere,” Mills remarked. “Any time there’s going to be mismatch in camouflage, there’s going to be natural selection.
“These are all animals that have lots of hungry predators.
“The question is: where might you expect to see fastest evolutionary change?” he mused.
Mills and his colleagues went looking for zones that had both colours–winter white and winter brown. All eight species in the study had them.
The research suggests the Canadian “polymorphic zone” for jackrabbits is along the eastern slopes of the Rocky Mountains in southern Alberta.
For hares, it seems to be along British Columbia’s coastal mountains.
“In these areas, where they have winter brown and winter white together, they have both forms,” Mills noted. “As the snow decreases, we expect the selection will be fastest in these polymorphic zones.
“They have that secret sauce for rapid evolution.”
Not only are the animals likely to evolve fastest in those areas to match the new climate reality, individuals are likely to spread into surrounding zones.
That’s a powerful argument for protecting those areas, said Mills, whose paper concludes only a small fraction of them currently enjoy some form of legal protection.
“If the target were conservation of this species, then we’d want to maintain polymorphic zones,” he reasoned.
Jackrabbits and hares are under little threat but other species are, and Mills suggests that looking for areas that have the largest diversity within a threatened species could be a powerful new way to approach conservation in the face of climate change.
“For any given species, are there certain traits that could be polymorphic and that would be especially sensitive areas that would benefit the species?” Mills wondered.
“This one just happens to be a visually-compelling trait but the processes are similar.
“My hope is that other people could come up with other traits for which there are these polymorphisms, this ‘secret sauce,’ and that that might be something that could be incorporated into conservation planning,” Mills said.