Confusing boundaries of the Labrador tea species: dispersal history explains the lack of clear species structure.

Background And Aims: The Labrador teas (genus Rhododendron, subsection Ledum) are a complex of species widely distributed in the Northern Hemisphere. They occupy cold-resistant plant communities from highlands to forest understorey and wetland habitats almost circumboreally and they are especially abundant in Northeast Asia and northern North America, yet there are no clear species boundaries in this group. The genetic structure of species of subsect.