How aspen genetics determine success in a changing climate

September 17, 2021

How species respond to climate change depends on factors such as environmental conditions, genetics, and the interactions between the two. In many species, understanding genetic compositions can help determine demography and population dynamics across environments, but much is yet to be understood in this field. 

In a study published in the journal Ecological Applications  last month, assistant professor of environmental science, policy, and management Benjamin Blonder and graduate student Courtenay Ray studied the regional genetic composition of the tree species quaking aspen, Populus tremuloides. Widespread across the Western United States, its range is shrinking and the species is in decline. 

The researchers studied the interactions between the aspens’ genetics and environmentally-driven mortality, collecting data from 503 test plots spread across Colorado. With collaborator Karen Mock at Utah State University, they conducted genetic sequencing to determine whether trees in each plot were diploid (two copies of each chromosome) or triploid (three copies of each chromosome). (In humans and most organisms, variation in chromosome copy number is usually lethal, but in plants, this variation actually can be adaptive in certain environments.) The results allowed Blonder and his co-authors to better understand how genetics, environment, and their interactions affect tree mortality and regeneration. 

The researchers found that triploid genotypes were vulnerable to mortality and had fewer new trees on drought-prone and ecologically disturbed plots, relative to diploids. Thus, chromosome copy number provides a useful and measurable predictor of aspen forest decline 

“Our study shows that triploid aspen, which often grow faster and larger, are actually more at risk in the hot and dry environments that will become more common in the future climate,” said Blonder. “We are now working towards scaling up this work across western North America in partnership with land managers.”

The study titled “Cytotype and genotype predict mortality and recruitment in Colorado quaking aspen (Populus tremuloides)”  and can be found on the journal Ecological Applications website. Other co-authors of the study have affiliations at Utah State University, Arizona State University, Stanford University, the University of Redlands, the Norwegian University of Science and Technology, and the Rocky Mountain Biological Laboratory. Several undergraduate student researchers contributed as co-authors to the study.