"The main implication is that we're really rolling the dice," said John Alroy, a paleobiologist at Macquarie University in Sydney, Australia. "We don't know which groups will suffer the most, which groups will rebound the most quickly, or which ones will end up with higher or lower long-term equilibrium diversity levels."
What seems certain is that the fate of each animal group will differ greatly, Alroy said.
His analysis, detailed in the Sept. 3 issue of the journal Science, is based on almost 100,000 fossil collections in the Paleobiology Database (PaleoDB).
The findings revealed various examples of diversity shifts, including one that took place in a group of ocean bottom-dwelling bivalves called brachiopods, which are similar to clams and oysters. They dominated the Paleozoic era from 540 million to 250 million years ago, and branched out into new species during two huge adaptive spurts of growth in diversity - each time followed by a big crash.
The brachiopods then reached a low, but steady, equilibrium over the past 250 million years in which there wasn't a surge or a crash in species' numbers, and still live on today as a rare group of marine animals. |
发表于 2010-9-3 09:02
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