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. His results are published in the Friday, February 27, issue of the journal Science.
"These are completely unexpected results," said Jablonski, Professor in Geophysical Sciences at the University of Chicago. 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.
"Maybe not all extinctions are created equal: it's not only how much you lose, but who," he said. Jablonski's findings may have implications for modern conservation strategies.
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 (K/T) boundary 65 million years ago, Jablonski 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, a great diversification of a few groups," said Jablonski. "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-first studied in 1988 by Thor Hansen from Western Washington University-Jablonski expected to find the same pattern in Europe.
"I was astounded when I found startling differences between Europe and North America," he said. "Europe lacks any kind of rapid expansion of 'bloom' taxa." Spurred by his findings, Jablonski burrowed into museum collections and investigated the collections of molluscan fossils for northern Africa and India.