A new theory on biodiversity co-signed by a member of the National Centre of Competence in Research "Plant Survival"

press release of April 23, 2003

An international team of researchers, including a biologist from the University of Neuchâtel, established a new theory on the abundance of species in function of ecological criteria. This remarkable work will be published by the American journal Proceedings of the National Academy of Sciences (PNAS) of April 29, 2003.

The researchers have perfected a model of universal importance capable of explaining why, within a community of reptiles or fish for example, certain species are more abundant than others regardless of the complexity of interactions involved. That is the challenge that were able to overcome, under the direction of George Sugihara of the Scripps Institution of Oceanography (San Diego, USA), Louis-Félix Bersier from the University of Neuchâtel (Switzerland), Robert May and Richard Southwood from the University of Oxford (United Kingdom) and Stuart Pimm from Duke University (Durham, USA).

"This theory applies just as well to birds that share the same environment. It will, for example, enable us to understand why in our forests the Brambling or the Blue Chickadee are abundant, whereas the Creeper or the Lesser Spotted Woodpecker are rare", explains the biologist from Neuchâtel, who is also a member of the National Centre of Competence in Research "Plant Survival". To better grasp the problem, Louis-Félix Bersier cites a study of a community of seven species of ducks (see picture*). These different species maintain a network of interactions not only among themselves, but also with their environment (habitat, prey, predators, etc.).

A binary model

How to unravel such a tangled web? By drawing a classification tree, where each branch represents a member of the community having a well-defined ecological characteristic. The beauty of this model is that each branch divides into two smaller branches.

"This tree, so structured with its dividing pairs of branches, constitutes the real key of the model", stresses Louis-Félix Bersier. If we take a community of birds as an example, one main branch can subdivide into 'seed-eating birds' on the one hand and 'insect-eating birds' on the other. The latter can equally branch out into 'species that catch insects while in flight' and 'species that grab them directly from the trees' and then this one dividing into 'species that find the insects in the bark' and 'species that pick them off the leaves'.

The branching continues until the successive characteristics are sufficient to unequivocally describe a single species of the community. In other words, each final twig of the classification arrives at one species of the community in question.

"The shape of the tree enables one to deduce the respective abundances of each species and to predict the evolution of their populations if certain environmental parameters were to change" sums up the biologist from Neuchâtel. The model was successfully tested on 10 animal communities: of birds, of fish, of reptiles and of amphibians. Therefore, this model is a tool that can be applied to a wide variety of organisms and appears to be very useful as the study of biological diversity is of high importance in ecology.

Picture caption: The shape of the tree enables one to deduce the respective abundances of species sharing the same environment.

Scientific article (pdf document)

for more information

Dr. Louis-Félix Bersier
University of Neuchâtel, Institute of zoology

Rédacteur: Igor Chlebny