Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Evolutionary "fast-track" in which the hunted outwit their hunters, could explain why human diseases progress so rapidly

17.07.2003


A water-dwelling rotifer (Brachionas calyciflorus) is surrounded by algae (Chlorella vulgaris) it hopes to eat by waving its cilia, at top, and drawing them into its mouth. In fresh water, these rotifers are barely visible as white specks while the microscopic algae are 100 times smaller. T.Yoshida and R.O. Wayne/Cornell University.


Glass chemostats like these, filled with water, nutrients, predators and prey - were used to demonstrate rapid evolution in a matter of weeks by Cornell biologists, including, from left, Nelson Hairston Jr., Stephen Ellner and Gregor Fussmann. Cornell University Photography Copyright © Cornell University


In the fishbowl of life, when hordes of well-fed predators drive their prey to the brink of extinction, sometimes evolution takes the fast track to help the hunted survive -- and then thrive to outnumber their predators.

This rapid evolution, predicted by Cornell University biologists in computer models and demonstrated with Pac-Man-like creatures and their algae food in laboratory habitats called chemostats, could play an important role in the ecological dynamics of many predator-prey systems, according to an article in the latest issue (July 17, 2003) of the journal Nature .

Physicians, the Cornell biologists say, should keep this rapid evolution in mind when investigating interactions between diseases and victims. As one example, they say, it is useful in trying to understand how HIV, the AIDS virus, manages to evolve so swiftly that development of improved vaccines is extremely difficult.



"Evolution is not just about dinosaurs and apes, but it can occur much more rapidly than we previously thought. Rapid evolution is pervasive, and the list of examples is growing," says Takehito Yoshida, a postdoctoral research fellow in Cornell’s Department of Ecology and Evolutionary Biology and lead author of the Nature article. Yoshida demonstrated the evolutionary principle with near-microscopic, multicelled animals called rotifers that live to gobble much tinier green algae. He notes, "We humans are part of complex ecosystems, and if we think we’re above the effects of evolution, we’re not looking close enough. If we want to understand epidemics and outbreaks of insects such as gypsy moths, we should not ignore the effect of evolution."

Other Cornell authors of the Nature report, illustrated with a cover photo of a rotifer-eating algae and the headline "Fast Food," are Laura E. Jones, a postdoctoral researcher, and Stephen P. Ellner, a professor of ecology and evolutionary biology, who conducted computer modeling of predator-prey dynamics; Gregor F. Fussmann, a postdoctoral researcher during the experiments and now a biologist at the University of Potsdam, Germany; and Nelson G. Hairston Jr., professor of ecology and evolutionary biology. The studies were supported by a grant from the Mellon Foundation.

The rotifers, Brachionas calyciflorus , and the algae, Chlorella vulgaris , were chosen for the experiment because they are the standard, well-documented "lab rats of freshwater predator-prey studies," Hairston says. The eaters and the eaten lived together for months in transparent glass chemostats stocked with nutrients (for the algae) and water.

The Hairston research group had noticed that the highs and lows of predator and prey populations in the chemostats were occurring completely "out of phase," says Yoshida. When rotifer populations were very high -- because previously they had plenty of algae to eat, algal populations hit rock bottom, because they had been consumed almost out of existence. The opposite occurred when algae were super-abundant: There were almost no rotifers around to eat them. Hairston and his collaborators were seeing weeks go by between the very pronounced oscillations in predator and prey populations.

Computer models developed by Ellner and graduate student Kyle Shertzer predicted that only evolution on the part of the prey could account for the out-of-phase, prolonged oscillation effect. Jones and Ellner refined the models to make detailed predictions about the effects of prey evolution, and Yoshida and Fussmann ran experiments in chemostats under two kinds of conditions: In one, all the single-cell algae were genetically identical clones -- essentially one-trick ponies that could not evolve their way out of a tough situation; in the second, the algal population was genetically varied so that somewhere among their tiny green gene pool might be an evolutionary innovation or two that could save them.

After running the chemostats for months and counting predator and prey populations day by day, the computer model’s prediction proved correct. Populations of a single algal clone quickly rose and fell almost in synchrony with the numbers of rotifers. But the algae with some genetic variation to draw on enjoyed longer periods when they were abundant and their predators were few -- along with agonizingly long periods when they struggled to rebuild their populations.

Instead of millions of years, the algae were evolving in a few weeks. But exactly how had they changed?

"We’re not sure," Hairston says. "We think that somehow they made themselves indigestible. They figured out how to pass straight through the rotifer gut without being digested and survived to make lots more of themselves. Rapid evolution got them out of a tight spot."

In one respect the joke is on the fast-evolving algae, Hairston notes, because they had to give up something to become indigestible: They became slow-growing algae relative to their kin. As a result, the next time they compete for food resources, the slow-growing, hard-to-eat algae will be at a disadvantage, and the more edible algae will thrive, allowing the cycle to repeat indefinitely.

Ellner suggests that this cycle of rapid evolution -- between defense and vulnerability -- could have parallels in human diseases. "There’s hardly anyone left in our [human] population who had resistance or developed it during the 1918 flu epidemic," he says. "Perhaps the time is now ripe for a return of those strains or their relatives."

Jones sees some hope that medical researchers will come to recognize the role of rapid evolution. "HIV is evolving so quickly that researchers are struggling to make an effective vaccine. As we say in our report, evolution can substantially alter predator-prey dynamics. Attempts to understand population oscillations cannot afford to neglect the potential effects of ongoing, rapid evolution."

Contact: Roger Segelken, Office: +1-607-255-9736, hrs2@cornell.edu

Roger Segelken | Cornell University News Service
Further information:
http://www.cornell.edu

More articles from Life Sciences:

nachricht Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University

nachricht How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>