Nature
PUBLISHED
When the worst drought on record struck parts of the US West Coast and Mexico, many plants didn’t make it. But against the odds, the scarlet monkeyflower managed to weather the hardship and continue thriving. Scientists have recently studied the case and believe they’ve found the first occurrence of a fascinating evolutionary mechanism in the wild.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Researchers from the University of British Columbia and Cornell University tracked 55 populations of scarlet monkeyflower (Mimulus cardinalis) in Oregon and California for more than a decade. During this time, starting in 2012, the region was hit by one of the most severe megadroughts in over 10,000 years, providing a rare opportunity to study how plant populations respond to extreme environmental stress.
By examining the plants' DNA, the team observed how genetic variants associated with climate tolerance shifted in frequency across some populations.
After the drought hit, certain monkeyflower populations rapidly gained more genetic variants and traits associated with hot, dry environments. As a result, their descendants were better able to retain water through their leaves while still sucking up carbon dioxide through photosynthesis. Crucially, the degree to which populations evolved turned out to predict how successfully they later rebounded.
“Essentially what we found is that the populations that recovered are also the populations that evolved the fastest,” Dr Daniel Anstett, study first author and assistant professor of plant biology at Cornell University, who conducted the research as a postdoctoral fellow at the University of British Columbia, explained in a statement.
“The plants that evolved fastest for drought recovered the fastest,” added senior author Dr Amy Angert, professor in the University of British Columbia's departments of botany and zoology. “And the ones that entered the drought with the right genetic variation were the ones that pulled themselves out of it the best.”
The researchers describe this as “evolutionary rescue”, the idea that a population can dodge extinction by evolving fast enough to keep pace with a changing environment. Confirming it had occurred required ticking three boxes: a climate-driven population decline, rapid genetic evolution, and a recovery attributable to that change. The scarlet monkeyflower checked all three, making it the first documented case of evolutionary rescue observed in the wild.
This is a rare smidgen of good news against an otherwise troubling backdrop. The findings suggest “evolutionary rescue” may help some species to cope with the extreme weather associated with climate change, whether it be heatwaves, droughts, intense downpours of rain, and the like. If so, some of the more doom-filled projections of climate-driven mass extinction may warrant a slight reassessment.
That said, the researchers are careful not to overstate the optimism. Many species do not carry enough genetic variation to make evolutionary rescue possible, so a key challenge going forward will be identifying which ones do and which don't.
“Not all species will be able to pull themselves up by their own bootstraps,” said Dr Angert. “The question becomes, which species are going to be like the monkeyflower, and which species are going to be more like Douglas fir or red cedar?”
“That’s the crystal ball we can use to predict into the future,” added Dr Anstett. “Identifying the genes involved in this evolution would help us understand what traits allow populations to survive these extended drought periods.”
The study is published in the journal Science.
