Featured Research

from universities, journals, and other organizations

Dispersal patterns key to invasive species' success

Date:
January 20, 2014
Source:
Duke University
Summary:
Using synthetic biology, engineers have tested the limits of the Allee effect, where a certain number of individuals are needed for a group to survive. 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 results have implications for both ecologists dealing with invasive species and medical practitioners fighting infections.

Rabbits crowded around a watering hole in southern Australia in 1938. This invasive species started with 24 individuals, reaching a population of 600 million by 1950 in part because of a phenomenon known as the Allee effect. A Duke University team has experimentally tested the concept in engineered bacteria.
Credit: Commonwealth of Australia (National Archives of Australia) 2013

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."

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."


Story Source:

The above story is based on materials provided by Duke University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Smith, R.P., Tan, C., Srimani, J.K., Pai, A., Riccione, K.A., Song, H., You, L. Programmed Allee effect in bacteria causes a tradeoff between population spread and survival. PNAS, January 2014

Cite This Page:

Duke University. "Dispersal patterns key to invasive species' success." ScienceDaily. ScienceDaily, 20 January 2014. <www.sciencedaily.com/releases/2014/01/140120173632.htm>.
Duke University. (2014, January 20). Dispersal patterns key to invasive species' success. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2014/01/140120173632.htm
Duke University. "Dispersal patterns key to invasive species' success." ScienceDaily. www.sciencedaily.com/releases/2014/01/140120173632.htm (accessed July 25, 2014).

Share This




More Plants & Animals News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

How to Make Single Serving Smoothies: Howdini Hacks

How to Make Single Serving Smoothies: Howdini Hacks

Howdini (July 24, 2014) Smoothies are a great way to get in lots of healthy ingredients, plus they taste great! Howdini has a trick for making the perfect single-size smoothie that will save you time on cleanup too! All you need is a blender and a mason jar. Video provided by Howdini
Powered by NewsLook.com
Boy Attacked by Shark in Florida

Boy Attacked by Shark in Florida

Reuters - US Online Video (July 24, 2014) An 8-year-old boy is bitten in the leg by a shark while vacationing at a Florida beach. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Newsy (July 24, 2014) A new study claims a set of prehistoric T-Rex footprints supports the theory that the giant predators hunted in packs instead of alone. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins