Migration History of Willamette Valley Aspens

Aspens are largely absent from the coast range and Willamette Valley of Oregon, however, they are abundant high in the Cascade Mountains. The rarity and physical location of aspens in the Willamette Valley suggest that they might have migrated by a very different path than the Cascade Aspens—namely by the catastrophic, glacial Missoula Floods that originated in the Rocky Mountains in Montana. They flooded the Willamette Valley several times about 10,000 years ago, depositing large rocks and soil. With the ability of aspen to spread vegetatively, it is reasonable to expect that they “surfed” down at the same time. We are testing this idea by using cutting-edge genotype-by-sequence (GBS) genome sequencing methods. If correct the rare Willamette aspens should resemble Rocky Mountain types more than nearby Cascade types. This project is funded by a crowd-funding campaign.

Results of genetic analysis have shown that far western/Pacific aspens are indeed a unique variety, but there is no evidence for a Rocky Mountain or flood origin in the trees we have studied. Results are summarized here and are undergoing further analysis and publication.