Lions and tigers are both FELINES. There is nothing extraordinary about this and it does not prove evolution from lower orders to higher, or from one completely different species to another. I don't think even creationists would argue that mutation does not exist. It is possible that these two animals had an ancestor - who was also a FELINE, and that a mutation occurred, possibly as a result of climate. Who knows. NO ONE DOES.
You and a lion are both mammals. If two felines can have a common ancestor, why can't two mammals? Explain the distinction.