More than two-thirds of Canada’s biodiversity is made up of species that occur within the country’s borders only at the very northern edge of their range. Biologists have long debated how much effort should be dedicated to conserving these “edge populations.” One argument in their favour is that they may be especially well suited to lead northward range shifts for their species as the climate warms.
Evolutionary ecologists Anna Hargreaves of McGill University and Chris Eckert of Queens University set out to find answers using a small flowering plant, Rhinanthus minor (also known as yellow rattle). ‘Admittedly it’s not the most charismatic plant’ say Hargreaves, ‘but it’s fantastic experimentally; we can plant seeds anywhere in the fall and by next fall they’ve completed their whole lifecycle. That lets us test whether plants are adapted to the elevation they come from, and whether they could survive above where the species currently grows. Hard to do that with animals!’
In a three-year experiment spanning 1,200 metres of elevation in Alberta’s Rocky Mountains, the researchers transplanted more than 20 000 seeds among elevations to see whether plants found the highest up the mountains were best suited to colonize even higher elevations. To test whether cool summers prevent the species from growing higher up the slopes, they warmed the air around some experimental plants by enclosing them in plastic cones that act like mini-greenhouses.