During California’s worst dry spell in the past 1,200 years, some populations of wildflowers defied the odds to survive the ordeal. Researchers say they now believe these flowers relied on a type of rapid genetic evolution — the first time such a phenomenon has been documented in the wild.The dry spell happened between 2012 and 2015, and killed more than 100 million trees. It was a particularly brutal period during an ongoing megadrought that began in 2000 and which has been made worse by climate change. Even though the drought killed plants that are normally drought-resistant, the scarlet monkeyflower, a bright red wildflower that thrives in wet areas, and along creek beds and springs, showed remarkable resilience.A team of researchers spent eight years studying 55 populations of the wildflower, whose scientific name is Mimulus cardinalis, by keeping track of its numbers in the wild and sequencing the flowers’ genomes to reveal genetic shifts.AdvertisementAdvertisement“We were able to show that these populations across the range in California were declining due to this extreme drought, and we found evidence of a rapid evolution across the genome,” said Daniel Anstett, an assistant professor at the School of Integrative Plant Science of Cornell University and first author of a study on the findings, which published Thursday in the journal Science. “And then we were able to relate a metric of this evolution to the ability of these populations to recover and to not go extinct.”While the entire species was not at risk of extinction, individual flower populations likely were, suffering declines of up to 90% compared to peak population sizes. It took about two to three years for these populations to rebound, according to Anstett.A stream in California is populated by monkeyflowers, which were studied in the newly published research. – Daniel AnstettThis rapid comeback is a process biologists call evolutionary rescue, which happens when a species is able to recover from the threat of extinction by an external factor such as a drought, Anstett explained. “Evolutionary rescue occurs when the few individuals that are left have the right genetic makeup to do better than the ones that died, so they do well or thrive within these new conditions, so the population inches back from extinction,” he said.Evolutionary rescue has been demonstrated in lab settings but researchers only had partial observations of it in the wild before: in cancer resistance in Tasmanian devils and adaptation to pollution in killifish. However, these studies did not provide full evidence that the process was taking place.AdvertisementAdvertisementThis study, Anstett said, offers rigorous evidence that evolution happened and it led to a demographic recovery. “We had a lot of information about the wildflowers’ demography and the genes, so that provided more ironclad information that ultimately evolutionary rescue was happening.”A great indicator of droughtThe scarlet monkeyflower is a perennial herb, meaning it regrows each season from the same roots. I …
