Many possible hypotheses can help explain the high levels of diversity in the tropics. Compare your response to the previous question to the possibilities below:

• Hypothesis #1: High speciation rates: The tropics are a “cradle” of diversity — in other words, the tropics are where species tend to be born.
• Hypothesis #2: Low extinction rates: The tropics are a “museum” of diversity — in other words, the tropics tend to harbor “old” species that, in other parts of the world, would go extinct.
• Hypothesis #3: High immigration rates: The tropics are a “destination” — a place where species that originated in other places end up invading and accumulating. Of course, we use the term destination loosely. This hypothesis doesn’t propose that species are aiming to move into the tropics — just that they somehow end up there.