Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.07.31.230375v1?rss=1 Authors: Ceulemans, R., Guill, C., Gaedke, U. Abstract: It is well known that functional diversity strongly affects ecosystem functioning. However, even in rather simple model communities consisting of only two or, at best, three trophic levels, the relationship between multitrophic functional diversity and ecosystem functioning appears difficult to generalize, due to its high contextuality. In this study, we considered several differently structured tritrophic food webs, in which the amount of functional diversity was varied independently on each trophic level. To achieve generalizable results, largely independent of parametrization, we examined the outcomes of 128,000 parameter combinations sampled from ecologically plausible intervals, with each tested for 200 randomly sampled initial conditions. Analysis of our data was done by training a Random Forest model. This method enables the identification of complex patterns in the data through partial dependence graphs, and the comparison of the relative influence of model parameters, including the degree of diversity, on food web properties. We found that the effects of functional diversity on any trophic level are intimately linked to the amount of diversity on other trophic levels, which may explain the difficulty in unifying results from previous studies. Strikingly, with high diversity throughout the whole food web, different interactions synergize to ensure efficient exploitation of the available nutrients and efficient biomass transfer, ultimately leading to a high biomass and production on the top level. The temporal variation of biomass showed a more complex pattern with increasing multitrophic diversity: while the system initially became less variable, eventually the temporal variation rose again due to the increasingly complex dynamical patterns. Importantly, top diversity and food web parameters affecting the top level were of highest importance to determine the biomass and temporal variability of any trophic level. Therefore, given its high ecological importance and vulnerability to global change, it is essential to preserve diversity on the top trophic level. Copy rights belong to original authors. Visit the link for more info