The Genetic Structure of a Redwood Gene Bank Across the Redwood Range
For those who have had the chance to stand in a redwood grove, there are few life experiences that compare. Ancient giants alive today have stood for centuries. But now they stand at a new crossroads of environmental change where urbanization, habitat fragmentation, pollution, invasive species and rapid climatic changes threaten them in ways they have not yet experienced in their long history on Earth.
Can these wonders of nature adapt to rapid climate change? With support from you, our members, Save the Redwoods League funds research to understand how to best protect redwood forests.
Researchers found in a 2007 study that coast redwoods’ genetic diversity was “very high” throughout the state, and more divergent in Central California. These Central California redwoods are most threatened by climate change and “should be a conservation priority,” said Richard S. Dodd, a professor of plant population genetics at the University of California, Berkeley.
Dodd and Vladimir Douhovnikoff, then a plant ecologist at Simmons College, conducted the study with the support of a League grant.
The 2007 study’s results are important because such genetic differences could affect how redwoods adapt to rapid climate change.
“We wanted to understand if there were major differences throughout coast redwoods’ range,” Dodd said.
From southern Oregon to Monterey County, California, a team led by Dodd and Douhovnikoff sampled the DNA of coast redwoods from 17 watersheds (areas where streams drain into larger bodies of water). To measure diversity, they looked at repeating motifs, or “microsatellites,” in the trees’ DNA—a technique that can highlight the effects of past events, such as glacial periods, that could have caused changes in the trees’ population sizes.
The researchers found that coast redwoods’ genetic diversity was “very high,” Dodd said, even within a single watershed. They also noticed a small but significant genetic difference between the broad, connected groves in Northern California and the more scattered, isolated groves in Central California. Dodd said the dividing line between the two types of trees likely lies somewhere in Marin County, between Sonoma and San Francisco Bay. Populations of trees growing to the south show more genetic differences than those growing to the north, he said, probably due to climate change in the past.
Dodd has observed a similar genetic divergence in other plant species that grow in Northern and Southern California. In species with a wider distribution in the north, he said, “the southern populations are often genetically a little different because of their small population size and their separation from each other — they are not exchanging genes.”
The same goes for groves of coast redwoods in Central California, which contain fewer individuals and have less genetic diversity.
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