Carolina Hemlock Populations are Isolated and Imperiled

Carolina hemlock (Tsuga caroliniana) is a rare Southern Appalachian tree species that is being devastated by an exotic insect. Researchers discovered that Carolina hemlock populations are highly genetically differentiated from each other and highly inbred. The results underscore the urgency of conserving the species’ genetic variation.

Carolina hemlocksUSDA Forest Service scientists and their partners are working to save native hemlock tree species from the hemlock woolly adelgid (HWA), an invasive insect from Japan. Carolina hemlock (Tsuga caroliniana) is particularly at risk because it occurs only in tiny isolated populations in the Southern Appalachians. A North Carolina State University scientist who cooperates with the Eastern Forest Environmental Threat Assessment Center led the first comprehensive molecular marker study of Carolina hemlock’s genetic diversity across the range of the species. Because the species is pollinated by wind, researchers expected to find small genetic differences among Carolina hemlock populations. Instead, they discovered that Carolina hemlock populations are highly differentiated from each other and highly inbred. Also, several populations have unique genetic variation not found elsewhere. These results, published in the journal Tree Genetics & Genomes, suggest that the species is not able to effectively disperse its seeds or pollen over long distances, increasing the isolation and vulnerability of individual populations. Scientists and land managers can apply the study results to target conservation efforts, to prioritize the populations where seed collection is most needed, and to inform HWA-resistant tree breeding programs.

Pictured: Researchers found that Carolina hemlock populations, like this one at Mount Jefferson State Park in North Carolina, are genetically isolated. Photo by Robert Jetton, North Carolina State University.

Related publications:

Forest Service Partners/Collaborators:
Southern Institute of Forest Genetics

External Partners/Collaborators: North Carolina State University

Contact: Kevin Potter, North Carolina State University Cooperating Scientist,

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