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 Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute

nachricht Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

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,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

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

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>