Over the hump

ECOLOGISTS USE THE POWER OF NETWORK SCIENCE TO CHALLENGE 30 YEAR HUMP THEORY

Written by Yvonne Buckley

For decades, ecologists have toiled to nail down general principles explaining why some habitats have so 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.

Yvonne Buckley (University of Queensland), Jennifer Firn (Queensland University of Technology), Joslin Moore (ARCUE), Suzanne Prober (CSIRO) and John Morgan (LaTrobe University) are the Australian members of an international team of ecologists that has pooled its resources to re-evaluate the relationship between species numbers and habitat productivity.

Five years ago a core group of ecological researchers in the USA formed the Nutrient Network or “NutNet”, a cooperative research initiative dedicated to investigating biodiversity and ecosystem processes in grasslands around the world.  Their innovative, standardized global sampling of 48 sites on five continents, including five sites across Australia (Photo 1 – Burrawan site, Qld), and has yielded an unprecedented data set.

 

The NutNet’s findings, which represent a significant advance in ecological thought, appear in the Sept. 23, 2011 issue of the journal Science (abstract online).

“Our study shows no clear relationship between productivity and the number of plant species in small study plots,” says lead author, Dr Peter Adler from Utah State University.

“We challenged a prevailing model developed in the early 1970s by British ecologist J. Philip Grime,” says Dr Adler. “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.

 “When I first heard about the Nutrient Network global project I thought we had a real chance to find out if this theory holds right around the world in different ecosystems”, says Dr Buckley. “The idea of doing a globally replicated experiment is very powerful and we have already found out some very exciting ecological principles”. (Photo 2 – Australian researchers in the field)

“This is ecology’s version of the Large Hadron Collider or Human Genome Project, we have to work across multiple sites in multiple different ecosystems from sub-tropical grasslands to Arctic tundra to find answers to the really big questions in ecology”, says Dr Buckley.

 “Our data emphasize the need to consider many factors to explain patterns of diversity – not just productivity alone,” Dr Adler says.

For the ecological community, Dr Adler says, NutNet’s current findings should spur ecologists to focus on other important factors regulating biodiversity, such as evolutionary history, disturbance and resource supply.

 “Our data emphasize the need to consider many factors to explain patterns of diversity – not just productivity alone,” Dr Adler says

“It’s time to remove outdated models from our textbooks and concentrate on more sophisticated approaches,” Dr Adler says. “That will improve our ability to predict the effect of environmental change on biodiversity.”

The full journal article detailing the research is also available online.

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