[DannyTN]

Well both tigers ans lions are considered cats. They might be one kind that has simply gotten to the point that it's difficult to mate. It's difficult to mate a dachshund with a St. Bernard too. If the dachshund is female the size will kill her.

Did you read the last line of the link you posted?

"Patrick (a li-liger) is one of the fortunate few and was saved through the generosity of The Roar Foundation. He now lives a life of ease and gets great enjoyment from spraying unwary "visitors. "

[Modernman]

Well both tigers ans lions are considered cats. They might be one kind that has simply gotten to the point that it's difficult to mate. It's difficult to mate a dachshund with a St. Bernard too. If the dachshund is female the size will kill her

Well, my Maine Coon is also a cat, but no way he's breeding with a female tiger. Though I'm sure he'd give it the old college try.

The liger example shows, IMO, that speciation is a gradual process with lots of gray areas. As species drift further apart, such as house cats and lions, it becomes clear that they are distinct. However, some species are still close enough that thay can interbreed.