捆绑SM社区

More than two-thirds of Canada鈥檚 biodiversity is made up of species that occur within the country鈥檚 borders only at the very northern edge of their range. Biologists have long debated how much effort should be dedicated to conserving these 鈥渆dge populations.鈥� 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 捆绑SM社区 and Chris Eckert of Queens University set out to find answers using a small flowering plant, Rhinanthus minor (also known as yellow rattle). 鈥楢dmittedly it鈥檚 not the most charismatic plant鈥� say Hargreaves, 鈥榖ut it鈥檚 fantastic experimentally; we can plant seeds anywhere in the fall and by next fall they鈥檝e 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!鈥�

In a three-year experiment spanning 1,200 metres of elevation in Alberta鈥檚 Rocky Mountains, the researchers transplanted more than 20听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 min-greenhouses.

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Their findings, in press at Ecology Letters, show that cool summers currently limit yellow rattle鈥檚 distribution, preventing it from growing at higher elevations. Plants from the species鈥� highest range edge have adapted to high-elevation summers by flowering earlier, so can make seeds where plants from lower elevations fail. But the experiments also yielded a surprising result: A high-elevation 鈥榮uper edge population鈥� from a nearby mountain outperformed all other populations in natural and warmed plots both at and above the species high-elevation range edge. So why haven鈥檛 the superior genes from this population spread to other high-elevation populations only a kilometer away? Researchers say this demonstrates that winning genotypes can get trapped in isolated edge populations, and that facilitating gene flow among edge populations might be a way to help them cope with environmental change.

Like most intensive experiments, this one focused on a single species. 鈥淥ur results are important not because they predict what other species will do, but because they are the first to show unexpected patterns that we as biologists need to start considering,鈥� Hargreaves says.

Three years of mountain fieldwork also produced some memorable moments. The field crew once scrambled up a chair-lift pole to evade a grizzly bear that ambled into the site to munch on berries. On another occasion, the researchers had to shovel snow to plant their last high-elevation sites for the season; then tobogganed downhill to get back to their car just before dark.

Yet at a time when fancy lab equipment and computer models increasingly dominate even ecological research, the project is also a reminder there鈥檚 sometimes no substitute for boots-on-the ground fieldwork.

鈥淭his study shows that important advances can still come 鈥� and sometimes can only come 鈥� from well-designed field experiments that require no expensive equipment, but creativity, vision and thousands of people hours,鈥� Hargreaves says. 鈥淚f we want to understand how the natural world works, we need to keep spending time in it.鈥�

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Caption 1: Artificial warming enables yellow rattle to flower high above its current distribution.

Caption 2:Warming chambers prove cool climates prevent yellow rattle from growing in alpine sites.

Caption 3: Researcher Anna Hargreaves toboggans back to the field vehicle after an early snow almost shuts the field season down.

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Local adaptation primes cold鈥恊dge populations for range expansion but not warming鈥恑nduced range shifts, by Anna L. Hargreaves and Christopher G. Eckert is published in Ecology Letters,

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To contact the researcher directly: anna.hargreaves [at] mcgill.ca