Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9. The Athabasca sand dunes, located on the south shore of Lake Athabasca in northern Alberta and Saskatchewan, Canada, are the largest northern dunes. Over 200 plant taxa occupy this region, but only 40 occur on open sands. Leaf anatomy and morphology were evaluated for endemic Salix taxa and their progenitors using light and scanning electron microscopy. Salix planifolia ssp.
Endemic willows have thicker cuticles than their widespread progenitors.
Compact leaf mesophyll in endemic Salix species suggests adaptation to this high light intensity environment.