Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Solved! Mystery that stumped ecosystem modelers

23.02.2012
Scientists show that predator/prey relationships make possible the rich biodiversity of complex ecosystems

As scientists warn that the Earth is on the brink of a period of mass extinctions, they are struggling to identify ecosystem responses to environmental change. But to truly understand these responses, more information is needed about how the Earth's staggering diversity of species originated.

Curiously, a vexing modeling mystery has stymied research on this topic: mathematical models have told us that complex ecosystems, such as jungles, deserts and coral reefs, in which species coexist and interact with another, cannot persist--even though they obviously do.

But now, Stefano Allesina and Si Tang, both of the University of Chicago, have solved that vexing modeling mystery, and have thereby laid the groundwork for improvements in the modeling of complex ecosystems to environmental change.

The researchers' work, which was funded by the National Science Foundation (NSF), is published in this week's issue of Nature.

The tension between mathematical models of ecosystems and the existence of the Earth's rich biodiversity was first exposed about 40 years ago by the development of a ground-breaking mathematical model that represented the relationship between ecosystem stability and diversity; the model was developed by Robert M. May of Oxford University.

According to May's model, ecosystems that harbor large numbers of interacting species would necessarily be extremely unstable--so unstable that even slight perturbations, such as variable weather and environmental conditions, would be enough to trigger massive extinctions within them. Therein lies a paradox: According to May's modeling, the persistence in nature of the complex ecosystems we observe should be exceedingly improbable.

Ever since May released his modeling results, scientists have been attempting to identify factors that enable species to persist despite the general tendency towards instability and extinctions highlighted by May's results. Now, in their Nature paper, Allesina and Tang explain why May's results do not accurately describe ecosystems in which "Eat or be eaten", relationships (predator/prey relationships) are prevalent. Allesina explains: "May's model assumes that any two species in a large ecological network interact with one another at random, and without any consideration of the specific type of interaction between them, whether it is a predator-prey relationship, a mutualistic relationship or a competitive relationship."

But in their recent research, Allesina and Tang modeled ecosystems in which species consume each other in addition to interacting with one another as competitors or mutualists. Their results explain why large numbers of species do, in fact, thrive instead of necessarily going extinct as predicted by May's model. This advance provides the foundation for the development of increasingly sophisticated analyses of ecosystem responses to environmental change.

Allesina believes that it is predator/prey relationships (not competitor or mutualistic relationships) that provide the necessary stability for almost infinite numbers of species to exist in ecosystems. They do so by keeping the size of species populations in check at supportable levels. Allesina explains, "When prey are high, predators increase and reduce the number of prey by predation. When predators are low, prey decrease and thus reduce the number of predators by starvation. These predator/prey relationships thereby promote stability in ecosystems and enable them to maintain large numbers of species."

By contrast, mutualistic relationships may reinforce the growth of large populations and competitive relationships may depress population numbers to the point of ecological instability. Allesina says that May's model mixed various types of species interactions but could not represent these relationships accurately because of technical modeling constraints that he and Tang overcame.

"The results of Allesina and Tang's network analyses are important," says David Spiller, an NSF program director, "because they show that the stability properties of complex ecological systems are determined by the type of interaction among species (predation, competition, mutualism) and the strength of those interactions."

Allesina says that he and Tang intend to further improve their ecosystem model by embedding into it well-known interactions that exist between particular species. He also says that the insights gleaned through this study may be used to improve models of other types of networks that are unrelated to ecology, such as various types of gene regulatory networks and chemical reactions.

Remarkably, Allesina says that he and Tang cracked the biodiversity mystery without supercomputers or other high-tech instruments that are so frequently at the core of current biological discoveries: "We did the necessary calculations with just a pen and paper after finding a 1988 article on quantum physics that gave us the key to crack the problem."

Lily Whiteman | EurekAlert!
Further information:
http://www.nsf.gov

More articles from Ecology, The Environment and Conservation:

nachricht New approach for environmental test on livestock drugs
27.07.2016 | Universität Zürich

nachricht Managing an endangered river across the US-Mexico border
18.07.2016 | International Institute for Applied Systems Analysis (IIASA)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Self-assembling nano inks form conductive and transparent grids during imprint

Transparent electronics devices are present in today’s thin film displays, solar cells, and touchscreens. The future will bring flexible versions of such devices. Their production requires printable materials that are transparent and remain highly conductive even when deformed. Researchers at INM – Leibniz Institute for New Materials have combined a new self-assembling nano ink with an imprint process to create flexible conductive grids with a resolution below one micrometer.

To print the grids, an ink of gold nanowires is applied to a substrate. A structured stamp is pressed on the substrate and forces the ink into a pattern. “The...

Im Focus: The Glowing Brain

A new Fraunhofer MEVIS method conveys medical interrelationships quickly and intuitively with innovative visualization technology

On the monitor, a brain spins slowly and can be examined from every angle. Suddenly, some sections start glowing, first on the side and then the entire back of...

Im Focus: Newly discovered material property may lead to high temp superconductivity

Researchers at the U.S. Department of Energy's (DOE) Ames Laboratory have discovered an unusual property of purple bronze that may point to new ways to achieve high temperature superconductivity.

While studying purple bronze, a molybdenum oxide, researchers discovered an unconventional charge density wave on its surface.

Im Focus: Mapping electromagnetic waveforms

Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.

Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...

Im Focus: Continental tug-of-war - until the rope snaps

Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases

Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

GROWING IN CITIES - Interdisciplinary Perspectives on Urban Gardening

15.07.2016 | Event News

SIGGRAPH2016 Computer Graphics Interactive Techniques, 24-28 July, Anaheim, California

15.07.2016 | Event News

Partner countries of FAIR accelerator meet in Darmstadt and approve developments

11.07.2016 | Event News

 
Latest News

New study reveals where MH370 debris more likely to be found

27.07.2016 | Earth Sciences

Dirty to drinkable

27.07.2016 | Materials Sciences

Exploring one of the largest salt flats in the world

27.07.2016 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>