Understanding Evolution

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Understanding Evolution

Latitudinal Diversity Gradient (The LDG)

Home → Visualizing life on Earth → Investigation Phase IV: Why the tropics? → Testing hypothesis #2: Are the tropics a museum? → The tropics are not much of a museum for foraminiferans

The tropics are not much of a museum for foraminiferans

The tropics as museumThe question of whether or not the tropical foraminiferans have extra-low extinction rates is not clear cut. Based on the graph below, they do seem to have slightly lower extinction rates — but not by much!

Citation: Wei, K., and Kennett, J. P. 1983. Nonconstant extinction rates of Neogene planktonic foraminifera. Nature 305: 218-220.

Let’s look at some more data relevant to this hypothesis. The pie chart below shows data on bivalves, not foraminiferans. It is fairly easy to understand. The chart shows what percent of bivalve genera living in different parts of the world have gone extinct over the past 16 million years.

 

Extinctions pie chart
David Jablonski, 2009, personal communication.

Question 10

Does the graph and pie chart above support the hypothesis that the tropics are a museum — in other words, that extinction rates are lower in the tropics than in other regions of the world? Or can you tell from these data? Explain your answer.

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The tropics are a museum for bivalves