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There are no wild ligers. Indeed, hybrids were once thought to be rare in nature—and of little consequence in an evolutionary sense. But now we know they can play an important role in speciation—the creation of new, genetically distinct populations.

As it turns out, hybridization in nature is quite common. Some 25 percent of plant species hybridize and some 10 percent of animals do the same.

“Hybridization as an event is rare,” said Jeremie Fant, a conservation scientist with the Chicago Botanic Garden who has worked on plant hybridization. “But in evolutionary history, it's been very common. Hybrids in the plant kingdom are everywhere. They are scattered through most lineages. When hybridization does occur, it can have important evolutionary impacts.”