To eat or be eaten: how do food webs come about ?

press release of February 26, 2004

Plants are often found at the origin of food chains. Hence, their survival depends on the links that exist between prey and predators that inhabit a certain ecosystem. A research on this theme co-funded by the NCCR Plant Survival has just been published in the February 26 issue of the prestigious journal Nature.

Louis-Félix Bersier, researcher at the University of Neuchâtel and the Swiss Federal Institute of Technology Lausanne, as well as Marie-France Cattin, PhD student at the University of Neuchâtel, are the principle authors of a new model that helps to better understand the establishment of trophic networks, in other words, the interactions between prey and predators within a community of living organisms. Supported by the Swiss National Science Foundation, this research is co-authored by Carolin Banasek-Richter, also PhD student at Neuchâtel, along with the participation of two mathematicians from the University of Fribourg, Richard Baltensperger and Jean-Pierre Gabriel.

The aim of the model, published in journal Nature, is to offer a graphic representation of the food web interactions between species that approaches reality as much as possible and can be applied to any ecosystem. The model enables one to deduct several properties arising out of the relationships between prey and predators, especially the proportion of species that are solely prey, or on the contrary, those that are only predators. One can also determine the percentage of omnivore or cannibalistic species and many other factors as well. Louis-Félix Bersier and his collaborators' research is original in that it shows that the food chains do not only depend on the capability of the individuals to adapt. The genetic factors acquired during evolution are equally decisive. The whole history of this diversification is condensed in the classification of species and the authors show that this phylogeny is an essential factor in order to understand the structure of the trophic networks.

One result of evolution is the acquisition of anatomical characteristics that facilitate the ingestion of a certain category of prey. For example, all warblers possess a beak that is perfectly adapted to pecking at insects. As for locusts of the Acrididae family, they all, without except, have mouthparts that make them excellent herbivores. "The fact that trophic relationships depend as much on phylogenetic constraints as on the capacity to adapt is something to be expected, admits Marie-France Cattin. However, it's the first time that these two arguments can be highlighted at the level of communities, in other words at a level greater than that of the species. Our model has been successfully tested on 7 communities comprising of between 30 and 180 species".

Even if it is, above all, fundamental research, the underlying ideas that this work puts forth could be applicable to areas other than trophic networks, such as, for example, the impact of climatic changes on the fauna and flora.

for more information

Louis-Félix Bersier
Institut de zoologie
Université de Neuchâtel
tel +41 32 718 30 06
fax + 41 32 718 30 01

Editor: Igor Chlebny