How do closely related species of alligators, at present, occur only in South-eastern United States and Eastern China? Explain.

Explanation

North American continent was connected with Eastern Asia in early Coenozoic era by a land bridge in the Bering Strait region. The climate of the whole region was much warmer than at present, and the alligators were distributed over the entire region. In late Coenozoic, due to glaciation (ice age), extinction of alligators took place. But alligators survived in South-eastern United States and Eastern China. Since the alligators of these regions have been separated for a long time, they have developed random mutations and have become slightly different.