Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Explosive Evolution Need Not Follow Mass Extinctions

14.02.2012
Following one of Earth’s five greatest mass extinctions, tiny marine organisms called graptoloids did not begin to rapidly develop new physical traits until about 2 million years after competing species became extinct.

This discovery, based on new research, challenges the widely held assumption that a period of explosive evolution quickly follows for survivors of mass extinctions.

In the absence of competition, the common theory goes, surviving species hurry to adapt, evolving new physical attributes to take advantage of newly opened niches in the ecosystem. But that’s not what researchers found in graptoloid populations that survived a mass extinction about 445 million years ago.

“What we found is more consistent with a different theory, which says you might expect an evolutionary lag as the ecosystem reforms itself and new interspecies relationships form,” said University at Buffalo geology professor Charles E. Mitchell, who led the research.

The research provides insight on how a new mass extinction, possibly one resulting from man-made problems such as deforestation and climate change, might affect life on Earth today.

“How would it affect today’s plankton? How would it affect groups of organisms in general?” asked the paper’s lead author, David W. Bapst, a PhD candidate at the University of Chicago, who studied with Mitchell as an undergraduate.

“The general motivation behind this work is understanding how extinction and evolution of form relate to each other, and the fossil record is the only place where we can do these sort of experiments across long spans of time,” Bapst said.

The research on graptoloids is scheduled to appear the week of Feb. 13 in the online Early Edition of the Proceedings of the National Academy of Sciences.

Other team members included Peter C. Bullock and Michael J. Melchin of St. Francis Xavier University in Nova Scotia, and H. David Sheets of Canisius College in Buffalo, N.Y. The National Science Foundation and Natural Sciences and Engineering Research Council of Canada supported the study.

Graptoloids are an extinct zooplankton that lived in colonies. Because the animals evolved quickly and had a wide geographic range, their fossil record is rich — a trove of information on how species diversify.

Bapst, Mitchell and their colleagues examined two different groups of graptoloids in their study: neograptines and diplograptines. Each kind lived during the Ordovician mass extinction that began about 445 million years ago, but only neograptines survived.

Before the extinction event, diplograptine species were dominant, outnumbering neograptine species. Diplograptines also varied more in their morphology, building colonies of many different shapes.

With diplograptines gone after the Ordovician mass extinction, neograptines had a chance to recover in an environment free of competitors.

According to the popular ecological release hypothesis, a popular theory, these circumstances should have led to a burst of adaptive radiation. In other words, without competition, the neograptines should have diversified rapidly, developing new physical traits — new colonial architectures — to take advantage of ecological niches that the diplograptines once filled.

But that’s not what the researchers found.

To test the adaptive radiation idea, they analyzed the colony forms of 183 neograptine and diplograptine species that lived before, during or after the Ordovician mass extinction — a total of 9 million years of graptoloid history.

This wealth of data enabled the team to track graptoloid evolution with more precision than past studies could. What the researchers discovered looked nothing like adaptive radiation.

Almost immediately following the Ordovician mass extinction, new neograptine species proliferated, as expected. But according to the study, these new species displayed only small changes in form or morphology, not the burst of innovation the release hypothesis predicts. In fact, graptoloids had been evolving new physical traits at a more intensive pace before the extinction event.

Limited morphological innovation among neograptines continued for approximately 2 million years after the extinction, Bapst said.

The lag supports a type of evolution that argues that interactions between co-evolving species help foster diversification. Because such relationships likely take time to develop in a recovering ecosystem, an evolutionary lag of the kind the graptoloid study detected should occur in the wake of a mass extinction.

Another possible explanation is that newly appeared graptoloid species may have differed in ways outside of physical traits, a phenomenon that biologists refer to as non-adaptive radiations. A third possibility is that graptoloids may have experienced evolutionary lag due to their complex mode of growth.

Besides investigating how neograptines fared after the extinction event, the team also analyzed whether colony form alone could explain why neograptines survived the mass extinction while diplograptines disappeared. The scientists concluded that this was unlikely, suggesting a role for other factors such as possible differences in the preferred habitat of the two groups.

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

More articles from Life Sciences:

nachricht Climate Impact Research in Hannover: Small Plants against Large Waves
17.08.2018 | Leibniz Universität Hannover

nachricht First transcription atlas of all wheat genes expands prospects for research and cultivation
17.08.2018 | Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Smallest transistor worldwide switches current with a single atom in solid electrolyte

17.08.2018 | Physics and Astronomy

Robots as Tools and Partners in Rehabilitation

17.08.2018 | Information Technology

Climate Impact Research in Hannover: Small Plants against Large Waves

17.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>