Study Proves Darwin's Theory That Productivity Increases Species Diversity
May 14, 2013

Study Proves Darwin’s Theory That Productivity Increases Species Diversity

April Flowers for - Your Universe Online

Charles Darwin predicted that a plot of land growing distantly related grasses would be more productive than a plot with a single species of grass in On The Origin of Species, first published in 1859. Over 150 years later, a new study from the University of Toronto Scarborough (UTSC), reveals Darwin was right; environments containing species that are distantly related to one another are more productive than those containing closely related species.

Since Darwin made the first prediction, many experiments have demonstrated that multi-species plots are more productive. Marc William Cadotte, assistant professor in UTSC´s Department of Biological Sciences, showed for the first time that species with the greatest evolutionary distance from one another have the greatest gains in productivity. The results of his study will be published in an upcoming issue of the Proceedings of the National Academy of Sciences (PNAS).

"If you have two species that can access different resources or do things in different ways, then having those two species together can enhance species function. What I've done is account for those differences by accounting for their evolutionary history," Cadotte says.

For his experiment, Cadotte grew 17 different plants in various combinations of one, two or four species per plot. He found multi-species plots produced more plant material, which was in line with previous studies. When analyzing the results, however, he also found combinations of plants that were distantly related were more productive than closely related combinations. A plot of goldenrod and black-eyed susan, which are closely related, weren´t as productive as a plot with goldenrod and bluestem grass, which are only distantly related.

Cadotte says there isn´t really a mystery to his results. Distantly related plants are more likely to require different resources than closely related plants, and to fill different environmental niches. For example, one might need more nitrogen, the other more phosphorus. Another plant might have shallow roots, while its partner has deep roots. In this way, they complement each other rather than compete for resources.

To predict productivity, according to the study´s findings, you only need to know evolutionary distance. This suggests that as plant species disappear, the Earth will become less productive.

This will lead to less carbon being pulled from the atmosphere by plants and possibly increasing the rate of global warming.

Cadotte says his results could be a valuable tool for conservation efforts. The information could be used by environmentalists trying to restore damaged habitats to pick which combinations of species to introduce.

An earlier study from an international team of scientists shows the loss of plant biodiversity, productivity and the rise of global warming could become a vicious cycle. That study, published in Nature Climate Change, demonstrates the dramatic loss of plant life that a slight upward shift — only 3.6 degrees Fahrenheit — could cause, claiming as much as half of common plant species and one-third of all animals could experience a serious decline in their habitat range.

“Our research predicts that climate change will greatly reduce the diversity of even very common species found in most parts of the world. This loss of global-scale biodiversity would significantly impoverish the biosphere and the ecosystem services it provides,” Dr. Rachel Warren of the University of East Anglia, said. “There will also be a knock-on effect for humans because these species are important for things like water and air purification, flood control, nutrient cycling, and eco-tourism.”