OSU study: Flocking behavior good for the ecosystem


In addition to being visually stunning, schools of herring, herds of wildebeest and countless other groups of organisms that act in concert can help complex ecosystems maintain their diversity and stability, according to new research from the Oregon State University.

Posted in Nature Ecology and Evolution, theto studydemonstrates that when individuals come together to consume resources as a collective group, the surrounding ecosystem is likely to be more resilient and able to support a wider range of species.

The results could be an important step towards understanding how living systems remain stable; collective behavior is ubiquitous on the planet, playing a leading role in everything from bacterial biofilms to human cities.

“These collectives exhibit highly organized, large-scale patterns of behavior that emerge spontaneously from localized interactions between nearby individuals,” said Ben Dalziel of OSU College of Science. “Our question was: what is the importance of collective behavior in ecosystems? “

Dalziel and his colleagues found that there was an emerging socio-ecological feedback between the size and structure of collective groups and the level of resources in an ecosystem, and that this feedback protected the system from collapse. The feedback smoothed out fluctuations in resource abundance and allowed more consuming species to persist using the same resource, instead of the stronger competitor pushing the weaker to extinction.

Dalziel, a population biologist, led a collaboration that examined the ecological importance of collective behavior through the prism of two lingering ecological puzzles: the enrichment paradox and the plankton paradox.

The enrichment paradox is observed when, in a predator-prey model, an increase in the food available to the prey leads to an unsustainable and destabilizing growth of the predator population. The plankton paradox refers to various ecological communities, such as different types of phytoplankton, persisting even though many similar species compete for limited resources.

“It doesn’t take for granted that complex ecosystems are stable – if you just put a group of species together in an environment, theory tells us that the result is likely to be ecosystem collapse,” said Dalziel. “This means that real ecosystems must have some kind of special sauce that allows them to persist with a wide range of species.”

It turns out that collective behavior – occurring among plants as well as microorganisms, animals and humans – could be a potent ingredient in the sauce, the researchers found.

Dalziel and Mark Novak of the College of Science, plus James Watson of the Oregon State College of Earth, Ocean, and Atmospheric Sciences and Stephen Ellner of Cornell University, started with a standard model of a simple food web: two ” generic consumers ”on a shared resource.

A battery of equations expresses the multiple variables of the model, such as consumer mortality rate and per capita resource consumption, but in this version of the model, consumers differ only in the efficiency with which they capture the resource. .

“We built simulations so that we could turn collective behavior on and off without changing anything else in the system,” said Dalziel. “What we found was that adding collective behavior changed the game in simulations – it stabilized ecosystems that, according to ecological and evolutionary theory, should not be stable otherwise.”

It was a piece of the knowledge puzzle that was missing, he said, noting that a lot of work had been done to understand how local individual behavior broadens to affect group-level behavior and how these groups deal. information, but not much about why the collective behavior occurs in the first place.

Dalziel calls the results “good news” which contrasts with the negative role that collective dynamics can play.

“Amid the challenges we face with the spread of disinformation online, which also involves collective dynamics, here is an example where collective behavior plays a fundamental role in sustaining life,” he said. . “And I also think it’s interesting that such an aesthetically striking aspect of ecosystems – flocks of birds, etc. – can also play an important role in their stability and diversity.”

The National Science Foundation, DARPA, the National Institutes of Health, and NASA supported this research.


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