The Norway maple (Acer platanoides), for example, evolved in northern Europe. When John Bartram introduced the tree to the Morris Arboretum of Philadelphia in 1756, this species had never before interacted with the plants, animals, and pathogens of North America (Nowak & Rowan 1990). Well into its third century of residence, the growth and reproduction of Norway maples is still influenced little or not at all by organisms native to this country.
