Navigation Links
Ancient marine invertebrate diversity less explosive than thought
Date:7/3/2008

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."


'/>"/>

Contact: Andrea Elyse Messer
aem1@psu.edu
814-865-9481
Penn State
Source:Eurekalert

Related biology news :

1. Ancient oak trees help reduce global warming
2. Ancient Mexican maize varieties
3. Archaeologist uses satellite imagery to explore ancient Mexico
4. Ancient protein offers clues to killer condition
5. Ancient Nutcracker Man challenges ideas on evolution of human diet
6. Ancient sunflower fuels debate about agriculture in the Americas
7. Ancient ecosystems organized much like our own
8. Synchrotron light unveils oil in ancient Buddhist paintings from Bamiyan
9. Ancient DNA: reconstruction of the biological history of Aldaieta necropolis
10. Ancient reptile rises from Alberta oil sands
11. Ancient lemurs little finger poses mystery
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/2/2017)... Feb. 2, 2017  EyeLock LLC, a market leader ... white paper " What You Should Know About Biometrics ... ensuring user authenticity is a growing concern. In traditional ... users. However, traditional authentication schemes such as username/password suffer ... Biometric authentication offers an elegant solution to the problem ...
(Date:1/31/2017)... CAMBRIDGE, Mass. , Jan. 31, 2017 /PRNewswire-USNewswire/ ... develop novel therapies for the treatment of bacterial ... generation set of antibacterial candidates from Pro Bono ... the increased prevalence of multi-drug resistant forms of ... by Cantab Anti Infectives Ltd, a PBB group ...
(Date:1/26/2017)...  Acuity Market Intelligence today released the 2017 ...  Acuity characterizes 2017 as a "breakout" year for ... a new understanding of the potential benefits these ... identity are often perceived as threats to privacy ... of Acuity Market intelligence. "However, taken together these ...
Breaking Biology News(10 mins):
(Date:2/24/2017)... ... February 24, 2017 , ... A study ... completed in an ambulatory surgery center (ASC) with satisfactory clinical and patient-reported outcomes, ... TDR studies. , Jake Lubinski, president of AxioMed, commented on the recent ...
(Date:2/24/2017)... , Feb. 24, 2017 Provectus Biopharmaceuticals, ... the "Company"), a clinical-stage oncology and dermatology biopharmaceutical ... deadline to participate in its previously announced rights ... of shares of common stock and Series C ... of listed warrants. As previously ...
(Date:2/24/2017)... N.J. , Feb. 24, 2017  Driven ... and biotechnology are now the fastest growing categories, ... Specialty Actives in Personal Care: Multi-regional Market ... research and management consulting firm Kline. ... bioprocesses that make them more effective for skin ...
(Date:2/24/2017)... Biologic Products, Inc. (NASDAQ: CBPO) ("China Biologic" or the "Company"), ... announced its financial results for the fourth quarter and fiscal ... Highlights Total sales in the fourth ... increased by 13.6% in USD terms to $77.6 million from ... Gross profit increased by 13.3% to $46.8 million from ...
Breaking Biology Technology: