Over the hump: Ecologists use power of network science to challenge long-held theory

Sep 22, 2011
Bugle lily at the Mt. Gilboa study site in South Africa. Credit: Image courtesy of Peter Wragg

For decades, ecologists have toiled to nail down principles explaining why some habitats have many more plant and animal species than others.

Much of this debate is focused on the idea that the number of species is determined by the productivity of the habitat.Shouldn't a patch of prairie contain a different number of species than an arid steppe or an alpine tundra?

Maybe not, says an international team of scientists that pooled its resources to re-evaluate the relationship between and habitat productivity.

The innovative, standardized global sampling of 48 sites on five continents yielded an unprecedented data set.

"Our study shows no clear relationship between productivity and the number of in small study plots," says Utah State University plant ecologist Peter Adler.

Scientists say Adler's and his colleagues' findings represent a significant advance in ecological thought. The findings appear in this week's issue of the journal Science.

"We challenged a prevailing model developed in the early 1970s by British ecologist J. Philip Grime," says Adler, lead author of the paper. "He proposed that the number of species rises then declines with increasing productivity."Though hotly debated, this "hump-shaped" model has remained a textbook standard for nearly four decades.

"In the search for underlying principles of ecology in a very complex natural world, it's inevitable that even long-standing and accepted theories will be debunked as more data are accumulated and synthesized," says Henry Gholz, program director in the National Science Foundation's (NSF) Division of , which funded the research.

In an "Emperor's New Clothes" moment, Adler remembers skeptical observations about the hump-shaped model made by graduate students in his classroom.

"'Why do ecologists spend so much time on this model when the evidence to support it is so weak?' they asked me," he says. "That was the kick I needed to pursue this question."

The challenge was daunting.

Existing, disparate case studies couldn't conclusively support Grime's unimodal pattern. Inconsistencies in data collection methods further hampered efforts to distill evidence to support the hump-shaped model. So Adler and fellow ecologists formed the Nutrient Network, or "NutNet," an NSF Research Coordination Network dedicated to investigating biodiversity and ecosystem processes in grasslands around the world.>Based at the University of Minnesota (UMN), the network is funded by an NSF grant to network organizers and UMN scientists Elizabeth Borer and Eric Seabloom.

"Our work not only sheds light on this classic question, it also demonstrates the power of a network approach," Borer says. "NutNet data are poised to inform many pressing ecological questions. Similar global, grassroots collaborations could help settle other longstanding scientific debates."

Says Gholz, "Research Coordination Networks are designed to facilitate these types of insights into the functioning of nature, insights that aren't possible in a focus on individual ecosystems."

Adler says that NutNet's data "emphasize the need to consider many factors to explain patterns of diversity--not just productivity alone."

NutNet's findings should spur ecologists to focus on other important factors regulating biodiversity, he says, such as evolutionary history, disturbance and resource supply.

"It's time to remove outdated models from our textbooks and concentrate on more sophisticated approaches," Adler says,"That will improve our ability to predict the effects of environmental change on biodiversity."

Explore further: A European bear's point of view, finally on film

Related Stories

Too much water, fertilizer bad for plant diversity

Mar 26, 2007

Too much of multiple good things -- water or nutrients, for example -- may decrease the diversity of plant life in an ecosystem while increasing the productivity of a few species, a UC Irvine scientist has discovered.

Recommended for you

Sharks contain more pollutants than polar bears

20 hours ago

The polar bear is known for having alarmingly high concentrations of PCB and other pollutants. But researchers have discovered that Greenland sharks store even more of these contaminants in their bodies.

Moth study suggests hidden climate change impacts

Apr 15, 2014

A 32-year study of subarctic forest moths in Finnish Lapland suggests that scientists may be underestimating the impacts of climate change on animals and plants because much of the harm is hidden from view.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Squirrel
3 / 5 (2) Sep 22, 2011
Why did it take skeptical observations by graduate students? Looks to me that science went on a holiday in ecology. Ioannidis (Why Most Published Research Findings Are False http://www.plosme...0020124) has shown how even in harder sciences than ecology most findings are not replicated in the long run. I blame overambitious "I am a genius" types that aggressively push their work through conference networking--a good way to ensure future reviewers (that have done friendly drinks with you) don't stop publication of doggy work.

More news stories

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.