Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Dispersal patterns key to invasive species' success

21.01.2014
Bacterial test of a theory has implications for ecology and infectious disease

In 1859 an Australian farmer named Thomas Austin released 24 grey rabbits from Europe into the wild because it "could do little harm and might provide a touch of home, in addition to a spot of hunting."


One of the most damaging invasive species in history, kudzu, or Japanese arrowroot, found its way from Japan to the southeastern United States, where it is overtaking much of the landscape. An ecological concept known as the Allee effect governs the spread of invasive species and pathogens, according to a Duke University team that has tested the concept in engineered bacteria.

Credit: Wikipedia Commons

By the end of the century, the rabbits had begun to overrun native ecosystems, reaching nationwide numbers of 600 million by 1950. They were propagating under a principle known as the Allee effect - the observation that larger groups of animals do better at establishing populations in a new environment. Had Austin instead spread the rabbits into many smaller groups across the landscape, things might have turned out differently.

With the help of E. coli and some clever synthetic biology techniques, engineers at Duke University have now tested the limits of the Allee effect. The results have implications for both ecologists dealing with invasive species and medical practitioners fighting infections.

Organisms exhibiting a very strong Allee effect need a certain number of individuals to survive, below which the group will collapse. And while intuition suggests that the more places a species spreads, the more it will thrive, scattering a population too thin by forming too many new colonies could result in the ruin of them all.

The paper appears online in the Proceedings of the National Academy of Sciences the week of Jan. 20.

"From the perspective of an invasive species, it appears to be a good idea to spread out to many different habitats simultaneously," said Lingchong You, associate professor of biomedical engineering at Duke. "If they all survive, the overall growth is much more efficient. But there's a catch because of the Allee effect; there is also a greater chance each population will fall below the critical threshold and every location will fail."

"This can offer insights for people managing invasive species," continued You. "If you limit the number of targets that an invasive species can travel

into, you might inadvertently help them thrive."

In the experiment, researchers engineered E. coli to produce a toxin that, left to its own devices, would soon wipe out the entire colony of bacteria. But they also put in a genetic switch that could turn their fortunes around; if enough bacteria were present and the chemicals they use to signal one another reached a certain concentration, they would begin producing an antidote to the toxin. In this way, the bacteria were engineered to have a high Allee effect.

The researchers then tested how well the bacteria did with different dispersal rates. They plucked the bacteria from their original source wells and colonized new ones. Each trial consisted of a different number of target habitats, which affected the density of the new populations.

Just as theory predicted, the greatest success came when the dispersion rate stayed in a happy middle ground. Too few new colonies and the bacteria barely spread; too many and each floundered, including the original source.

The results also have important medical implications, according to You.

"People need to use caution when using antibiotics," said You. "Our bodies' natural microbes are in some ways the first line of defense against invaders, which can often stop an infection from gaining a foothold. But if we recklessly apply antibiotics, we may destroy these defenses and make it easier for just a few foreign bacteria to spread and grow. We may remove their Allee effect."

Their work was supported in part by the National Science Foundation grant CBET-0953202 and the National Institutes of Health grant 1R01GM098642.

CITATION: "Programmed Allee effect in bacteria causes a tradeoff between population spread and survival," Smith, R.P., Tan, C., Srimani, J.K., Pai, A., Riccione, K.A., Song, H., You, L. PNAS, Jan. 20, 2014. DOI: 10.1073/pnas.1315954111

Ken Kingery | EurekAlert!
Further information:
http://www.duke.edu

More articles from Ecology, The Environment and Conservation:

nachricht Bioinvasion on the rise
15.02.2017 | Universität Konstanz

nachricht Litter Levels in the Depths of the Arctic are On the Rise
10.02.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Organ-on-a-chip mimics heart's biomechanical properties

23.02.2017 | Health and Medicine

Light-driven reaction converts carbon dioxide into fuel

23.02.2017 | Life Sciences

Oil and gas wastewater spills alter microbes in West Virginia waters

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>