These massive, old trees were found to have thousands of genetic mutations. A study from the University of British Columbia has revealed that hundred-year-old Sitka spruce trees growing on Vancouver Island contain a remarkably high amount of genetic variation. In a single tree, the team found up to 100,000 genetic differences between the base and the tip of the crown.
The research team sequenced the DNA collected in bark and needle samples from 20 trees in Carmanah Walbran Provincial Park. Each genetic difference that was identified represents a somatic mutation, which is a modification that occurs over the natural course of growth rather than during conception.
“This is the first evidence of the tremendous genetic variation that can accumulate in some of our tallest trees,” said study lead author Professor Sally Aitken. “Scientists have known for decades about somatic mutations, but very little about how frequently they occur and whether they contribute significantly to genetic variation. Now, thanks to advances in genomic sequencing, we know some of the answers.”
The investigation was focused on the Sitka spruce because it is among the tallest trees growing in the Pacific Northwest.
“Because these trees live so long and grow so tall, they’re capable of accumulating tremendous genetic variation over time,” explained study co-author Vincent Hanlon. “On average, the trees we sampled for the study were 220 to 500 years old and 76 meters tall. There’s a redwood tree in California that’s 116 meters tall, but these Sitka spruce were pretty big.”
According to the researchers, further studies are needed to understand how the different somatic mutations will affect the evolution of the species.
“Most of the mutations are probably harmless, and some will likely be bad,” said Professor Aitken. “But other mutations may result in genetic diversity and if they’re passed onto offspring they’ll contribute to evolution and adaptation over time.”
“We often see tree populations that adapt well to local climates and develop effective responses to changing stresses such as pests and bugs. Our study provides insights on one genetic mechanism that might help make this possible.”
The study is published in the journal Evolution Letters.
Image Credit: TJ Watt