Article in Science reveals new trends in ecological networks

New studies on ecological networks highlight the importance of individual species for the conservation of communities. The trend was revealed in an article analyzing recent studies in the area and penned by a Brazilian scientist and his Argentine colleague

By Fábio de Castro

Agência FAPESP – With the aim of investigating the organization of interactions among species in ecological communities, recent studies have utilized different strategies that vary from mathematical modeling to comparative or experimental field studies.

Regardless of the approach utilized, one common theme emerges from these studies: the crucial importance of certain individual species to conserve the communities and the functional maintenance of ecosystems.

This trend in studies on ecological networks was highlighted in an article published in the current edition of Science magazine by Thomas Lewinsohn, professor of the Biology Institute of the Universidade Estadual de Campinas (UNICAMP) and Luciano Cagnolo, of the Multidisciplinary Institute of Vegetal Biology at Universidad Nacional de Córdoba (Argentina).

The article was published in the Perspectives section of the magazine, in which internationally renowned specialists offer commentary and evaluate recent advances on a specific topic.

Lewinsohn and Cagnolo were invited to comment on three articles published in Science between February and March. The articles, presented different ways of investigating the organization of interactions among species in ecological communities.

In September 2011, Lewinsohn, who is president of the Brazilian Association of Ecological Science and Conservation (ABECO), coordinated the São Paulo School on Ecological Networks, under the auspices of the São Paulo Advanced School of Sciences (ESPCA), a FAPESP- funded project. Twelve leading researchers and 40 students from Brazil and 14 other countries participated.

The article discusses the different approaches utilized in the three studies and examines the applicability of these works to the evaluation ofe the importance of a species for the functional maintenance of ecosystems. In addition, the article highlights future research priorities in ecological networks.

According to Lewinsohn, the three studies use very different approaches. One study employed a mathematical model and used complex data on different ecological systems.

The other two studies were conducted in the field. One: scrutinized the interactions among diverse biological components of an agroecosystem in England, and another utilized a series of small hills located in the plateaus south of Buenos Aires, Argentina. This study, analyzed possible links between the characteristics of these hills and changes in the organization of ecological networks.

“These are very diverse studies. We analyzed the strategy of each study in an attempt to evaluate how to justify the strategic importance of each species for the organization of those communities. In every case, it involved observing a set of species to detect which ones have a key role in the functional maintenance of the community,” comments Lewinsohn to Agência FAPESP.

Unlike studies that choose a certain species because of its rarity or vulnerability with the objective of guiding conservation practices, these works seek to determine which species are the touchstone of every community. A touchstone species is one whose loss: has the potential to underminethe functionality of the entire ecological system.

“ The trend that we identified is to apply new theoretical tools to detect the functional contributions of different species and to thereby increase the predictive capacity of these studies. Detecting these key species is not a trivial matter. To do so, one must analyze the functional organization of the system and understand it through models and experiments,” affirms Lewinsohn.

The article that described an experiment with an agrosystem in England, for example, has shown that certain species of plants play a critical role in the system’s stability.

“When these species of plants were withdrawn, the whole system fell apart, with a domino effect that reached parasites and predators. In thiscontext, what is fundamental is not the importance of each plant species in itself, but its importance in relation to all species that are linked to it,” explains Lewinsohn.

Systems and behaviors

According to Lewinsohn, the ecological networks area, which has grown at an accelerated pace for the past 10 years, involves the application of complete network theory. This is a theory based on mathematics and physics that is applied to the study of the organization and interactions characterizing ecological communities.

“Our analysis indicates that we are arriving at the end of the first, exploratory phase of research on ecological networks. The tendency is for us to enter a second phase that offers greater expectations that these studies will allow us to understand very important phenomena in ecology, boosting our capacity to make forecasts.”

Predictive capacity, according to the profession, is especially crucial for ecological studies. “We want to understand how different ecological systems behave given the global changes underway in climate, conversion of soil use, and circulation of exotic invasive species. At the same time, we want to use this knowledge to make forecasts that allow us to mitigate the effects of these changes, preserving the functional properties of ecosystems and the services that they render,” says Lewinsohn.

The article “Keystones in Tangled Bank,” by Thomas Lewinsohn and Luciano Cagnolo, can be read by subscribers of Science magazine at: www.sciencemag.org/content/335/6075/1449.summary.