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 Transforming plant cells from generalists to specialists
07.12.2016 | Duke University

nachricht What happens in the cell nucleus after fertilization
06.12.2016 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Predicting unpredictability: Information theory offers new way to read ice cores

07.12.2016 | Earth Sciences

Sea ice hit record lows in November

07.12.2016 | Earth Sciences

New material could lead to erasable and rewriteable optical chips

07.12.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>