Plants Demonstrate Rapid Evolution to Climate Change, But Face Limits
Recent research across two independent studies has documented plants' capacity for rapid genetic evolution in response to climate change impacts, including extreme heat and prolonged drought. While one multi-site experiment with Arabidopsis thaliana observed adaptation but identified extreme heat as a limiting factor leading to extinction for some populations, another study tracking natural populations of scarlet monkeyflowers in California and Oregon provided the first comprehensive documentation of "evolutionary rescue" from climate change in the wild, enabling populations to recover from severe drought.
Both studies underscore the critical role of genetic diversity in facilitating adaptation.
Multi-Site Experiment Documents Arabidopsis thaliana Adaptation and Limits
A multi-site study led by Moisés Expósito-Alonso and the Genomics of rapid Evolution to Novel Environment (GrENE) network consortium investigated the speed of plant evolution under varying climate stresses. This significant research was published on March 26 in the journal Science.
The study involved simultaneous experiments across 30 distinct climate zones in Western Europe, the Mediterranean, the Middle East, and North America. From fall 2017 through spring 2022, genetically diverse populations of Arabidopsis thaliana were planted in 12 plots at each of the 30 locations.
An analysis of genomic data from the first three years, encompassing three generations and 360 distinct experiments, indicated that in most instances, the plants genetically adapted to their new environments. Researchers observed evolutionary tempo within three to five years, with adaptive DNA variants increasing in frequency. Genetic alterations varied across different climates but showed similarities within comparable climates, suggesting repeatability. Genes involved in sensing heat stress and controlling flowering time were among those most affected.
Conversely, the study also revealed that some populations did not adapt efficiently enough for survival, particularly in the warmest environments. Populations exhibiting predictable evolutionary changes survived, while those with chaotic genetic changes became extinct.
This suggests that while rapid adaptation is possible, extreme heat can reduce population sizes, potentially pushing them towards an evolutionary breaking point.
The study involved a consortium of approximately 75 scientists who annually collected flower clippings and sequenced the whole genomes of over 70,000 surviving plants from more than 2,500 pooled samples. Expósito-Alonso, a UC Berkeley assistant professor of integrative biology, stated that understanding the speed of evolution and associated genetic shifts is crucial for developing models to identify at-risk plants and animals and to inform conservation strategies.
Scarlet Monkeyflowers Exhibit Evolutionary Rescue in the Wild
Separately, a study published in Science documented "evolutionary rescue" in natural populations of scarlet monkeyflowers (Mimulus cardinalis) during California's severe drought from 2012 to 2015. Researchers, led by Daniel Anstett, an assistant professor of plant biology, tracked these populations in Oregon and California for over a decade, beginning in 2010.
The study provides the first comprehensive documentation of evolutionary rescue from climate change in natural populations. This phenomenon involves a species recovering from an extinction threat due to rapid genetic adaptation. Some scarlet monkeyflower populations experienced declines of up to 90% but remarkably rebounded within two to three years.
Researchers utilized stored seeds and whole-genome sequencing from 55 populations to establish a genetic baseline and track climate-associated variations. They observed rapid evolution across the genome, linked to the populations' ability to recover and avoid extinction. Three populations particularly thrived, exhibiting the most adaptation at climate-associated genetic sites. These adaptations appear linked to variations in the plant's stomata and carbon assimilation during photosynthesis, exhibiting a "drought avoidance" strategy by developing more slowly, living longer, and growing less rapidly.
Anstett noted that genetic variations observed before the drought were found to predict demographic recovery five to seven years later, suggesting a potential for predictive genetics in species survival under future extreme weather events. External experts described the research as significant for demonstrating evolutionary rescue in real-time and providing a critical model for using genomics to predict species vulnerability to climate change.
Broader Implications for Climate Change Adaptation
Both studies highlight that rapid evolution in response to climate stressors is possible, given sufficient genetic diversity within populations. The Arabidopsis study indicates that while adaptation can occur quickly, extreme heat can overwhelm the evolutionary capacity of some populations, leading to extinction. The scarlet monkeyflower study provides evidence that rapid, whole-genome adaptation can enable populations to recover from severe climate-induced declines in natural settings.
Researchers involved in both studies continue their investigations, analyzing later generations and initiating new experiments to understand the long-term effects of these adaptations and to identify specific genetic variants. The findings from these studies contribute to understanding plants' potential for resilience against climate change and underscore the importance of genetic diversity in conservation efforts.