Preserving the Hemlock

March 4, 2008

As part of an ongoing effort to preserve the imperiled eastern hemlock tree species, researchers from North Carolina State University have successfully located the most genetically diverse populations of the species in the southern portion of its range. They hope that by collecting the seeds from these trees the species–which is suffering both from insect infestation and prolonged drought conditions–can be saved from extinction.

Dr. Kevin Potter, research assistant professor in the Department of Forestry and Environmental Resources at NC State, and colleagues from Camcore, the largest international tree conservation partnership in the world, surveyed 20 separate populations of eastern hemlock in the southeastern United States to determine which ones contained the most genetic diversity. Their findings appear in the March edition of the journal New Forests.

Eastern hemlock (Tsuga canadensis) is an aesthetically and ecologically important species of tree found from eastern Canada to the Great Lakes states and south along the entire Appalachian mountain range. Since the hemlock tends to grow alongside streams, it plays an important role in regulating water temperature, and its loss could affect the many species of fish and insect life that inhabit mountain streams.

The tree is threatened by the prolific spread of an exotic insect known as the hemlock wooly adelgid (Adelges tsugae), which kills the trees in as few as four years. In the past decade, the hemlock wooly adelgid has infested more than 50 percent of the eastern portion of the hemlock's range, and the number is expected to grow because the adelgid, an introduced species from Asia, has no natural predators in North America.

Some researchers believe the best hope for the tree's salvation lies in "ex situ," or "off-site," preservation efforts, like those spearheaded by Camcore. Ex situ preservation involves collecting seeds from a species and planting them in preservation areas in other countries, with the hope that the species can one day be reintroduced.

Potter and his colleagues studied 20 populations of eastern hemlock scattered throughout the Southeast, an area believed to have served as a population refuge for the tree during the last ice age. They discovered the greatest genetic variation in isolated populations located on the eastern side of the Appalachian range, with a trend of decreased genetic diversity moving west into the Appalachians and to the opposite side of the mountain chain. The results will guide Camcore's collection efforts.

"You need as much genetic diversity as possible in your sample," says Potter, who conducted the research while a post-doctoral fellow with Camcore. "When a species goes through this sort of a 'genetic bottleneck' event, where its numbers really decline, you may find that the survivors may express traits that are beneficial in terms of surviving insect infestation, but that they've lost traits that help them survive other events, like drought. For preservation to be successful, you need trees with the largest possible variety of beneficial traits."

Source: NC State University, by Tracey Peake

Explore further: Flies released to attack hemlock-killing pest

Related Stories

Study reveals how eastern US forests came to be

May 20, 2015

Plant hunters traveling between North America and Asia in the 1800s noticed a bizarre pattern: collections they brought back from China and Japan were strikingly similar in their leaves, flowers and fruits to plants from ...

Recommended for you

What would a tsunami in the Mediterranean look like?

August 27, 2015

A team of European researchers have developed a model to simulate the impact of tsunamis generated by earthquakes and applied it to the Eastern Mediterranean. The results show how tsunami waves could hit and inundate coastal ...

Intensity of desert storms may affect ocean phytoplankton

August 27, 2015

Each spring, powerful dust storms in the deserts of Mongolia and northern China send thick clouds of particles into the atmosphere. Eastward winds sweep these particles as far as the Pacific, where dust ultimately settles ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.