Eastern hemlock (Tsuga canadensis (L.) carrière): Perspectives from its northwestern range limit

Eastern hemlock (Tsuga canadensis (L.) Carrière) is a slow-growing and longlived conifer in the Pinaceae family. Its range extends from Nova Scotia west into Wisconsin and Minnesota and south along the Appalachian Mountains, northern Georgia, and Alabama, with outlier populations along the western range limits in Minnesota, Ohio, Indiana, Georgia, Alabama, Kentucky, and Tennessee. Eastern hemlock is a foundation species across its range that has transformational effects on its surrounding ecosystem. As of 2013, eastern hemlock has been listed as near threatened due to the presence of an invasive insect, the hemlock woolly adelgid (Adelges tsugae Anaand.), which is destroying populations in the eastern United States. Eastern hemlock has historically existed at its northwestern range limit in Minnesota in disjunct and marginal populations, and it is listed as endangered in the state. There are trees of known and suspected native provenance scattered across state and municipal parks and public gardens. In addition to its natural populations, eastern hemlock has long been an ornamental plant produced by the nursery industry and is propagated via vegetative cuttings and, less commonly, seed. The genetic diversity of native and cultivated eastern hemlock trees can be elucidated using DNA techniques such as microsatellite markers. Understanding the geographic areas that confer the greatest genetic diversity or sites that contain unique alleles can help prioritize the conservation and preservation of land. A combination of ecology, horticulture, conservation genetics, and strong professional partnerships will help ensure the survival of eastern hemlock in the United States.