Diverse recovery pattern from mass extinction.

A study by University of Chicago paleontologist David Jablonski shows that recoveries from mass extinctions differ widely from one geographical region to another, even though the extinction intensities and patterns are more or less the same everywhere. "These are completely unexpected results," he says. He found that regions differed greatly from each other not only in terms of which species diversified and how quickly, but also in the ratio of surviving local species to foreign invaders.

Jablonski's is the first study that has looked at the geographical variation of recovery patterns on a region-by-region basis. Focusing on the mass extinction event that killed the dinosaurs, at the Cretaceous/Tertiary boundary 65,000,000 years ago, he found that recovery rates in North America and Europe were very different even though they are at roughly the same latitude.

"In North America, there was a large pulse of `bloom' taxa [groups], a great diversification of a few groups. This phenomenon is analogous to a plankton bloom or weed growth after some ecological disturbance." After seeing the pattern of bloom taxa in North America, Jablonski expected to find the same pattern in Europe. Instead, "I was astounded when I found startling differences between Europe and North America. Europe lacks any kind of rapid expansion of `bloom' taxa." Spurred by his findings, Jablonski examined museum collections and investigated the collections of molluscan fossils for northern Africa and India. He found that the Gulf Coast of North America differed from all three regions, not just in respect to bloom taxa, but in other aspects.

For any mass extinction, the flora and fauna that appear afterwards comprise three major...