Parallel evolution of leaf pubescence in Encelia in coastal deserts of North and South America

Members of the shrub genus Encelia occur in the arid coastal regions of western North America and South America along gradients of precipitation extending from less than 50 mm annually to somewhat over 350 mm. At moist ends of the gradient species possess glabrate, green leaves. Proceeding to drier regions, the species possess progressively more pubescent, whiter leaves. Leaf absorptance to solar radiation decreases with precipitation in an identical pattern along gradients in both North and South America.