Hares adapting to climate change, study suggests
Research finds evolutionary ‘secret sauce’
Research suggests hares and jackrabbits 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 Thursday 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’s paper looks at eight, 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,” said Mills. “Anytime 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?”
Mills and his colleagues went looking for zones that had both colours — winter white and winter brown.
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 B.C.’s coastal mountains.
“In these areas, where they have winter brown and winter white together, they have both forms,” Mills said. "As the snow decreases, we expect the selection will be fastest in these polymorphic zones.”
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.