Researchers from Canada’s University of British Columbia spent last northern summer scaling these giant Sitka spruce trees (Picea sitchensis) in Vancouver Island’s Carmanah Valley, collecting bark and needles.
They are old (220 to 500 years) as well as big (76 metres tall on average). The trees that is, not the researchers.
What they (the researchers) found, is that a single old-growth tree can have up to 100,000 genetic differences in DNA sequence between the base and the tip of the crown.
Each difference, says study leader Sally Aitken, represents a somatic mutation, or a mutation that occurs during the natural course of growth rather than during reproduction.
“This is the first evidence of the tremendous genetic variation that can accumulate in some of our tallest trees,” she says.
“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.”
Studying somatic mutation rates can shed light on how trees, which can’t evolve as rapidly as other organisms like animals due to their long lifespans, nonetheless survive and thrive, Aitken says.
The findings are published in the journal Evolution Letters.