@misc{CeulemansGaedkeKlauschiesetal.2019, author = {Ceulemans, Ruben and Gaedke, Ursula and Klauschies, Toni and Guill, Christian}, title = {The effects of functional diversity on biomass production, variability, and resilience of ecosystem functions in a tritrophic system}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {744}, issn = {1866-8372}, doi = {10.25932/publishup-43543}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-435439}, pages = {16}, year = {2019}, abstract = {Diverse communities can adjust their trait composition to altered environmental conditions, which may strongly influence their dynamics. Previous studies of trait-based models mainly considered only one or two trophic levels, whereas most natural system are at least tritrophic. Therefore, we investigated how the addition of trait variation to each trophic level influences population and community dynamics in a tritrophic model. Examining the phase relationships between species of adjacent trophic levels informs about the strength of top-down or bottom-up control in non-steadystate situations. Phase relationships within a trophic level highlight compensatory dynamical patterns between functionally different species, which are responsible for dampening the community temporal variability. Furthermore, even without trait variation, our tritrophic model always exhibits regions with two alternative states with either weak or strong nutrient exploitation, and correspondingly low or high biomass production at the top level. However, adding trait variation increased the basin of attraction of the high-production state, and decreased the likelihood of a critical transition from the high- to the lowproduction state with no apparent early warning signals. Hence, our study shows that trait variation enhances resource use efficiency, production, stability, and resilience of entire food webs.}, language = {en} } @article{CeulemansGaedkeKlauschiesetal.2019, author = {Ceulemans, Ruben and Gaedke, Ursula and Klauschies, Toni and Guill, Christian}, title = {The effects of functional diversity on biomass production, variability, and resilience of ecosystem functions in a tritrophic system}, series = {Scientific Reports}, volume = {9}, journal = {Scientific Reports}, publisher = {Macmillan Publishers Limited}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-019-43974-1}, pages = {16}, year = {2019}, abstract = {Diverse communities can adjust their trait composition to altered environmental conditions, which may strongly influence their dynamics. Previous studies of trait-based models mainly considered only one or two trophic levels, whereas most natural system are at least tritrophic. Therefore, we investigated how the addition of trait variation to each trophic level influences population and community dynamics in a tritrophic model. Examining the phase relationships between species of adjacent trophic levels informs about the strength of top-down or bottom-up control in non-steadystate situations. Phase relationships within a trophic level highlight compensatory dynamical patterns between functionally different species, which are responsible for dampening the community temporal variability. Furthermore, even without trait variation, our tritrophic model always exhibits regions with two alternative states with either weak or strong nutrient exploitation, and correspondingly low or high biomass production at the top level. However, adding trait variation increased the basin of attraction of the high-production state, and decreased the likelihood of a critical transition from the high- to the lowproduction state with no apparent early warning signals. Hence, our study shows that trait variation enhances resource use efficiency, production, stability, and resilience of entire food webs.}, language = {en} } @article{WojcikCeulemansGaedke2021, author = {Wojcik, Laurie Anne and Ceulemans, Ruben and Gaedke, Ursula}, title = {Functional diversity buffers the effects of a pulse perturbation on the dynamics of tritrophic food webs}, series = {Ecology and Evolution}, volume = {11}, journal = {Ecology and Evolution}, number = {22}, publisher = {John Wiley \& Sons, Inc.}, address = {Hoboken (New Jersey)}, issn = {2045-7758}, doi = {10.1002/ece3.8214}, pages = {15639 -- 15663}, year = {2021}, abstract = {Biodiversity decline causes a loss of functional diversity, which threatens ecosystems through a dangerous feedback loop: This loss may hamper ecosystems' ability to buffer environmental changes, leading to further biodiversity losses. In this context, the increasing frequency of human-induced excessive loading of nutrients causes major problems in aquatic systems. Previous studies investigating how functional diversity influences the response of food webs to disturbances have mainly considered systems with at most two functionally diverse trophic levels. We investigated the effects of functional diversity on the robustness, that is, resistance, resilience, and elasticity, using a tritrophic—and thus more realistic—plankton food web model. We compared a non-adaptive food chain with no diversity within the individual trophic levels to a more diverse food web with three adaptive trophic levels. The species fitness differences were balanced through trade-offs between defense/growth rate for prey and selectivity/half-saturation constant for predators. We showed that the resistance, resilience, and elasticity of tritrophic food webs decreased with larger perturbation sizes and depended on the state of the system when the perturbation occurred. Importantly, we found that a more diverse food web was generally more resistant and resilient but its elasticity was context-dependent. Particularly, functional diversity reduced the probability of a regime shift toward a non-desirable alternative state. The basal-intermediate interaction consistently determined the robustness against a nutrient pulse despite the complex influence of the shape and type of the dynamical attractors. This relationship was strongly influenced by the diversity present and the third trophic level. Overall, using a food web model of realistic complexity, this study confirms the destructive potential of the positive feedback loop between biodiversity loss and robustness, by uncovering mechanisms leading to a decrease in resistance, resilience, and potentially elasticity as functional diversity declines.}, language = {en} } @article{CeulemansGuillGaedke2021, author = {Ceulemans, Ruben and Guill, Christian and Gaedke, Ursula}, title = {Top predators govern multitrophic diversity effects in tritrophic food webs}, series = {Ecology : a publication of the Ecological Society of America}, volume = {102}, journal = {Ecology : a publication of the Ecological Society of America}, number = {7}, publisher = {Wiley}, address = {Hoboken}, issn = {0012-9658}, doi = {10.1002/ecy.3379}, pages = {16}, year = {2021}, 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, because of 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 bottom-up and top-down effects cascade simultaneously throughout the food web, intimately linking the effects of functional diversity of any trophic level to the amount of diversity of other trophic levels, which may explain the difficulty in unifying results from previous studies. Strikingly, only with high diversity throughout the whole food web, different interactions synergize to ensure efficient exploitation of the available nutrients and efficient biomass transfer to higher trophic levels, 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 because of the increasingly complex dynamical patterns. Importantly, top predator diversity and food-web parameters affecting the top trophic level were of highest importance to determine the biomass and temporal variability of any trophic level. Overall, our study reveals that the mechanisms by which diversity influences ecosystem functioning are affected by every part of the food web, hampering the extrapolation of insights from simple monotrophic or bitrophic systems to complex natural food webs.}, language = {en} } @phdthesis{Ceulemans2021, author = {Ceulemans, Ruben}, title = {Diversity effects on ecosystem functions of tritrophic food webs}, doi = {10.25932/publishup-50325}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-503259}, school = {Universit{\"a}t Potsdam}, pages = {vii, 166}, year = {2021}, abstract = {There is a general consensus that diverse ecological communities are better equipped to adapt to changes in their environment, but our understanding of the mechanisms by which they do so remains incomplete. Accurately predicting how the global biodiversity crisis affects the functioning of ecosystems, and the services they provide, requires extensive knowledge about these mechanisms. Mathematical models of food webs have been successful in uncovering many aspects of the link between diversity and ecosystem functioning in small food web modules, containing at most two adaptive trophic levels. Meaningful extrapolation of this understanding to the functioning of natural food webs remains difficult, due to the presence of complex interactions that are not always accurately captured by bitrophic descriptions of food webs. In this dissertation, we expand this approach to tritrophic food web models by including the third trophic level. Using a functional trait approach, coexistence of all species is ensured using fitness-balancing trade-offs. For example, the defense-growth trade-off implies that species may be defended against predation, but this defense comes at the cost of a lower maximal growth rate. In these food webs, the functional diversity on a given trophic level can be varied by modifying the trait differences between the species on that level. In the first project, we find that functional diversity promotes high biomass on the top level, which, in turn, leads to a reduction in the temporal variability due to compensatory dynamical patterns governed by the top level. Next, these results are generalized by investigating the average behavior of tritrophic food webs, for wide intervals of all parameters describing species interactions in the food web. We find that the diversity on the top level is most important for determining the biomass and temporal variability of all other trophic levels, and show how biomass is only transferred efficiently to the top level when diversity is high everywhere in the food web. In the third project, we compare the response of a simple food chain against a nutrient pulse perturbation, to that of a food web with diversity on every trophic level. By joint consideration of the resistance, resilience, and elasticity, we uncover that the response is efficiently buffered when biomass on the top level is high, which is facilitated by functional diversity on every trophic level in the food web. Finally, in the fourth project, we show that even in a simple consumer-resource model without any diversity, top-down control on the intermediate level frequently causes the phase difference between the intermediate and basal level to deviate from the quarter-cycle lag rule. By adding a top predator, we show that these deviations become even more likely, and anti-phase cycles are often observed. The combined results of these projects show how the properties of the top trophic level, including its functional diversity, have a decisive influence on the functioning of tritrophic food webs from a mechanistic perspective. Because top species are often among the most vulnerable to extinction, our results emphasize the importance of their conservation in ecosystem management and restoration strategies.}, language = {en} } @misc{WojcikCeulemansGaedke2021, author = {Wojcik, Laurie Anne and Ceulemans, Ruben and Gaedke, Ursula}, title = {Functional diversity buffers the effects of a pulse perturbation on the dynamics of tritrophic food webs}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1251}, issn = {1866-8372}, doi = {10.25932/publishup-55373}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-553730}, pages = {25}, year = {2021}, abstract = {Biodiversity decline causes a loss of functional diversity, which threatens ecosystems through a dangerous feedback loop: This loss may hamper ecosystems' ability to buffer environmental changes, leading to further biodiversity losses. In this context, the increasing frequency of human-induced excessive loading of nutrients causes major problems in aquatic systems. Previous studies investigating how functional diversity influences the response of food webs to disturbances have mainly considered systems with at most two functionally diverse trophic levels. We investigated the effects of functional diversity on the robustness, that is, resistance, resilience, and elasticity, using a tritrophic—and thus more realistic—plankton food web model. We compared a non-adaptive food chain with no diversity within the individual trophic levels to a more diverse food web with three adaptive trophic levels. The species fitness differences were balanced through trade-offs between defense/growth rate for prey and selectivity/half-saturation constant for predators. We showed that the resistance, resilience, and elasticity of tritrophic food webs decreased with larger perturbation sizes and depended on the state of the system when the perturbation occurred. Importantly, we found that a more diverse food web was generally more resistant and resilient but its elasticity was context-dependent. Particularly, functional diversity reduced the probability of a regime shift toward a non-desirable alternative state. The basal-intermediate interaction consistently determined the robustness against a nutrient pulse despite the complex influence of the shape and type of the dynamical attractors. This relationship was strongly influenced by the diversity present and the third trophic level. Overall, using a food web model of realistic complexity, this study confirms the destructive potential of the positive feedback loop between biodiversity loss and robustness, by uncovering mechanisms leading to a decrease in resistance, resilience, and potentially elasticity as functional diversity declines.}, language = {en} }