Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bivalve Census Reveals Echo of Ancient Mass Extinction

10.02.2009
Paleontologists can still hear the echo of the death knell that drove the dinosaurs and many other organisms to extinction following an asteroid collision at the end of the Cretaceous Period 65 million years ago.

“The evolutionary legacy of the end-Cretaceous extinction is very much with us. In fact, it can be seen in virtually every marine community, every lagoon, every continental shelf in the world,” said University of Chicago paleontologist David Jablonski. It is, he said, “sort of an echo of the big bang for evolutionary biology.”

This conclusion followed a detailed global analysis of marine bivalves, one of the few groups plentiful enough in the fossil record to allow such a study, which was funded by the National Aeronautics and Space Administration. Andrew Krug of the University of Chicago, Jablonski and James Valentine of the University of California, Berkeley, examined the geologic ages of every major lineage of living bivalves the world over, from oysters and scallops to quahogs and cockles. Their report appears in the Feb. 6 issue of the journal Science.

International biological census

The team followed procedures similar to taking a census of everyone living in Chicago, inferring birth rates from that age profile, and then comparing them to a census for Tokyo, Mexico City and other major international metropolitan areas.

Their analysis quantified the time of origin for 711 lineages of bivalves living in the oceans today, and converted them to evolutionary origination rates. In all but the highest-latitude locations, the team saw the clear signs of a strong increase in origination rates following the end of the Cretaceous.

That was no great surprise, Jablonski said, because “the post-extinction recovery pulse is dramatic—we’ve known about it for a long time.” The surprising finding was that the initial 10 million-year boom never really went bust. The origination rate slowed a bit, but did not drop back to the levels that preceded the mass extinction. “It was as if the post-war baby boom birth rate slowed slightly but never returned to pre-war levels,” he said.

Why the origination rate failed to drop to previous levels remains an unsolved question, “one that we never even would have asked if we hadn’t analyzed the data in this new way,” Jablonski noted. “It could be that the extinction took out competitors that had been holding the bivalves back, and permanently opened more room to diversify. Or the post-extinction increase in predation by crabs, fish and other enemies may have spurred the bivalves to keep evolving at a faster pace.” These will be interesting ideas to test next, according to Jablonski.

There’s a subtlety to the findings. “These data don’t mean that the extinction was less severe at high latitudes. They mean that the recovery was less prolific at high latitudes,” he said.

Tropical recovery engine

The difference reflects the lag between when lineages arise in the tropics and when they finally make it up into polar waters. “The tropics were the engine of the recovery, and they just kept on pumping out new lineages,” Jablonski said, while the poles slowly collected lineages spreading out from warmer zones.

The paper culminated a discussion among the authors that had nothing to do with the end-Cretaceous extinction, said Krug, a Postdoctoral Scholar in Geophysical Sciences at Chicago. They were following up other work that Krug had done on the interplay between the geographic range, age and species composition of modern lineages.

When they compared the data from several provinces, Krug noticed the same statistical blip in each—a sharp kink in the curve summing up the ages of living lineages. “When we saw that the kink fell right at 65 million years ago, we knew we had something,” Jablonski said. Upon further analysis, a significant pattern emerged for origination rates, an evolutionary signal that had withstood 65 million years of later global changes in climate, geography and ecology.

“It turned out to be supported in almost all the provinces, and the strength of that support was predictable based on latitude of the province,” Krug said. “We’d found a pattern no one had ever seen before. It was an exciting moment.”

Steve Koppes | Newswise Science News
Further information:
http://www.uchicago.edu

More articles from Life Sciences:

nachricht Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care

nachricht Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>