Several years ago a popular bumper sticker proclaimed, "Free Gondwanaland!" referring to the now-separated supercontinent that once united Africa, South America. Australia and India. While the bumper sticker was obviously facetious, we have already biologically united not only Gondwanaland, but also Laurasia—the North American, European and Asian supercontinent.Over the last few centuries, we have intentionally and unintentionally moved thousands of species into areas of the world where they, or even species like them, have never before occurred. One of the most common reasons for introducing plant species into new areas is for ornamental or landscape purposes. With these introductions, we have often set into motion interactions between species that we could not have predicted and cannot control.
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