Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ancient marine invertebrate diversity less explosive than thought

07.07.2008
Diversity among the ancestors of such marine creatures as clams, sand dollars and lobsters showed only a modest rise beginning 144 million years ago with no clear trend afterwards, according to an international team of researchers. This contradicts previous work showing dramatic increases beginning 248 million years ago and may shed light on future diversity.

"Some of the time periods in the past are analogies for what is happening today from global warming," says Jocelyn Sessa, doctoral candidate in geosciences, Penn State. "Understanding what happened with diversity in the past can help us provide some prediction on how modern organisms will fare. If we know where we have been, we know something about where it will go."

Using contemporary statistical methods and the Paleobiology Database, the researchers report, in today's (July 4) issue of Science, a new diversity curve that shows that most of the early spread of invertebrates took place well before the Late Cretaceous, and that the net increase through the period since, is proportionately small relative to the 65 million years that elapsed.

One key to the new curve is the Paleobiology Database, (http://paleodb.org) housed at the National Center for Ecological Analysis and Synthesis, University of California, Santa Barbara. Previous research was based on databases of marine invertebrate fossils that recorded only the first occurrence of an organism and the last occurrence of the organism. There was no information in between for the organism.

"Over 30 years ago, researchers looked at the curve they had and considered that perhaps diversity did not increase at all," says Mark E. Patzkowsky, associate professor of geosciences. "What researchers saw was the diversity curve leveled off for quite some time and then took off exponentially. However, diversity results are strongly controlled by sampling techniques."

The new database allows researchers to standardize sample size because it includes multiple occurrences of each fossil. Researchers can randomly choose equal samples from equal time spans to create their diversity curve. This new curve uses 11 million-year segments, but the researchers hope to reduce the time intervals to 5 million years to match the interval of the previous curve, known as Sepkoski.

The data for this study contains 284,816 fossil occurrences of 18,702 genera that equals about 3.4 million specimens from 5384 literature sources. The old curve, developed by J. John Sepkoski Jr., used a database that contained only about 60,000 occurrences.

The researchers also looked at evenness in diversity. If there are 100 specimens divided into 10 time intervals, they could be divided with 10 individual specimens in each interval; or 91 specimens could be in one interval with one each in the remainder. The more even the distribution, the higher the evenness.

"Evenness says something about resource distribution," says Patzkowsky. "Much of invertebrate diversity has been attributed to diversity increase in the tropics, but the curve is not driven by that totally. It seems that 450 million years ago was not so different from today because it also contained more diversity in the tropics."

The major points of the Sepkoski curve are still seen in the new curve. Some things that are not seen, such as the decrease in diversity due to the Cretaceous Tertiary (KT) extinction 65 million years ago are not visible because of the scale of the intervals used. The extinction and recovery in the KT took less than 11 million years and so do not show. Some things not seen on the Sepkoski curve include a peak in the Permian. Also unexpected is that the diversity in the Jurassic (206 to 144 million years ago) is lower than diversity in the Triassic (248 to 206 million years ago), indicating a dip and rise in the diversity curve. The curve then rises in the Cretaceous and remains more or less flat after that. The previously thought exponential increase in diversity is not there.

"Comparing diversity through time is about how our world works, about the origin of species and how diversity changes with temperature," says Sessa. "If we think that the net increase over time will not get much greater, things are very different from if the diversity increases exponentially."

Andrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu

More articles from Earth Sciences:

nachricht Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

nachricht Shallow soils promote savannas in South America
20.10.2017 | Senckenberg Forschungsinstitut und Naturmuseen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>