When a lion and a tiger cross paths in nature, they usually compete. They do not fall in love. They do not form families. Their territories, instincts, and lifestyles are different. Yet under rare and ...

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 ...

A good way to start an argument among biologists is to ask them what seems a simple question: "What is a species?" To evolutionary theorists, a species is a fundamental unit, and transitions between ...