Navigation Links
Species have come and gone at different rates than previously believed
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 of 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 a paleobiology database, the researchers report in the 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. The research team was led by John Alroy of the University of California at Santa Barbara.

One key to the new curve is the Paleobiology Database, (http://paleodb.org/cgi-bin/bridge.pl) 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 of Penn State. "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: Lily Whiteman
lwhitema@nsf.gov
703-292-8310
National Science Foundation
Source:Eurekalert  

Related biology news :

1. Census of Marine Life lists 122,500 known species, over halfway to complete inventory by Oct. 2010
2. New bee checklist lets scientists link important information about all bee species
3. World-class environment vision to bring back the species
4. First successful reverse vasectomy on endangered species performed at the National Zoo
5. Threatened or invasive? Species fates identified
6. Mysterious mountain dino may be a new species
7. Bee species outnumber mammals and birds combined
8. New catfish species named for museum mail supervisor
9. The cormorant -- the black plague or an example of successful species conservation?
10. A survivor in Greenland: A novel bacterial species is found trapped in 120,000-year-old ice
11. A Great Lakes mystery: The case of the disappearing species
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Species have come and gone at different rates than previously believed
(Date:5/16/2017)... , May 16, 2017  Veratad Technologies, LLC ( ... online age and identity verification solutions, announced today they ... Conference 2017, May 15 thru May 17, 2017, in ... and International Trade Center. Identity impacts ... and in today,s quickly evolving digital world, defining identity ...
(Date:5/6/2017)... May 5, 2017 RAM Group ... a new breakthrough in biometric authentication based on ... mechanical properties to perform biometric authentication. These new sensors ... material created by Ram Group and its partners. This ... transportation, supply chains and security. Ram Group is ...
(Date:4/19/2017)... New York , April 19, 2017 ... competitive, as its vendor landscape is marked by the ... the market is however held by five major players ... Safran. Together these companies accounted for nearly 61% of ... of the leading companies in the global military biometrics ...
Breaking Biology News(10 mins):
(Date:10/12/2017)... ... October 12, 2017 , ... ... platform specifically designed for life science researchers to analyze and interpret datasets, ... Franklin, who made a major contribution to the discovery of the double-helix ...
(Date:10/11/2017)... Md. (PRWEB) , ... October 11, 2017 , ... ... digital pathology, announced today it will be hosting a Webinar titled, “Pathology is ... Advanced Pathology Associates , on digital pathology adoption best practices and how Proscia ...
(Date:10/11/2017)... ... 11, 2017 , ... Singh Biotechnology today announced that the ... its novel anti-STAT3 (Signal Transducer and Activator of Transcription 3) B VHH13 single ... the cell membrane and bind intracellular STAT3 and inhibit its function. Dysregulation of ...
(Date:10/10/2017)... 10, 2017 International research firm Parks Associates announced ... at the TMA 2017 Annual Meeting , October 11 in ... residential home security market and how smart safety and security products impact ... Parks Associates: Smart Home ... "The residential security market has ...
Breaking Biology Technology: