A classical result in ecology, known as the biodiversity - ecosystem functioning (BEF) relationship, is that communities with increased biodiversity have increased stability and productivity. This result emerged mostly from experiments conducted in plant communities, which explains why the resulting theoretical framework focused on ecological mechanisms resulting from competition between species (functional complementarity in resource use and selection of the strongest competitor), to the detriment of trophic interactions. While this classical biodiversity - functioning positive relationship holds in more realistic communities, composed of several trophic levels, two communities with the same composition will have different functioning given the structure of their food web. This results in a higher variability of the relationship, and makes it more difficult to make accurate predictions in empirical communities, as we have little understanding of the mechanisms involved. It then begs the question as to whether and how much the structure of the communities' food webs, in addition to their biodiversity, influences ecosystem functioning. Here, we used simulation of biomass dynamics in food-webs to study the relative impact of several aspects of food-webs structure on species complementarity and the strength of the selection effect, and analyzed the resulting BEF relationship.
Results/Conclusions
The organisation of trophic interactions in an ecological community can result in different shapes of the BEF relationship, depending on the emerging structural properties of the food web. This is caused by an interplay between the height of the food web (the number of trophic levels), the consumer complementarity in both resources and predators and the producers complementarity in nutrient use. Producers complementarity remains an important driver of ecosystem functioning, but its effect can be dampen by consumers diversity. Communities with increased consumers diversity indeed have a stronger selective effects on producers, even more so if their height is important. Which results in an increased functioning. But the importance of this increase depends on the consumers complementarity in both predator and resources. These properties all have been independently identified as potential drivers of functioning in food webs, but understanding their relative strength, and the way they ultimately shape the BEF relationship allows us to build a better mechanistic framework for BEF in real world communities. Which will ultimately result in a better predictive framework.