|Credit: U.S. Geological Survey|
Many genera of plants in temperate eastern North America are also represented in eastern Asia. This separation is referred to as disjunction, as demonstrated by our native tulip tree, Liriodendron tulipifera and its Chinese relative, Liriodendron chinense.
Intercontinental disjunct taxa are presumed to have originated from a common ancestor millions of years ago when physical connections existed between the North American and Eurasian continents. These ancestors were split into geographically isolated populations due to continental drift, while climate changes rendered some extinct. Eventually, distinctly different and geographically separated, but related species evolved. Other genera in the Arboretum with intercontinental disjunct species include Cornus, Sassafras, and Campsis.
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