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533 results on '"Gaedke, Ursula"'

6. Integrating different facets of diversity into food web models: how adaptation among and within functional groups shape ecosystem functioning.

Author

Wojcik, Laurie Anne, Klauschies, Toni, Velzen, Ellen van, Guill, Christian, and Gaedke, Ursula

Subjects
FOOD chains, BIOMASS, FUNCTIONAL groups, GENETIC variation, SOCIAL interaction
Abstract

Adaptation of communities to environmental fluctuations can emerge from different facets of biodiversity, which may impact ecosystem functioning differently. Previous work in the field of biodiversity–ecosystem functioning (BEF) examined how ecosystem functions can be influenced by two sources of adaptive potential: sorting – i.e. changes in community composition due to fitness differences – can occur when multiple species or groups are present (richness), and trait adaptability – i.e. trait adjustments within species or functional groups – can emerge from genetic or phenotypic diversity. However, their effect is typically studied separately, and often in the context of only one trophic level. Therefore, we used a trait‐based, multispecies predator–prey model to investigate how sorting and trait adaptability, at one or two trophic levels, separately or jointly shape ecosystem functions and properties, such as total biomass, production, biomass‐weighted mean trait, relative top–down control and synchrony. We found that the adaptive potential emerging from any facet of diversity induced changes in trophic interactions, in turn affecting biomass distributions within and across trophic levels, dynamical behaviour, and synchrony of biomass dynamics within a trophic level. Particularly, sorting and trait adaptability could contribute to a similar degree and at a similar time to temporal changes in ecosystem functions, but their respective contribution depended on the speed of trait adaptation, the trait range between similar functional groups and trophic interactions. We thus suggest to consider multiple facets of diversity and their corresponding sources of adaptive potential to deepen our mechanistic understanding of BEF relationships, especially in the context of rapid biodiversity change. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Long-term cyclic persistence in an experimental predator-prey system

Author

Blasius, Bernd, Rudolf, Lars, Weithoff, Guntram, Gaedke, Ursula, and Fussmann, Gregor F.

Subjects
Life cycles (Biology) -- Observations, Predation (Biology) -- Analysis, Plankton populations -- Observations, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Predator-prey cycles rank among the most fundamental concepts in ecology, are predicted by the simplest ecological models and enable, theoretically, the indefinite persistence of predator and prey.sup.1-4. However, it remains an open question for how long cyclic dynamics can be self-sustained in real communities. Field observations have been restricted to a few cycle periods.sup.5-8 and experimental studies indicate that oscillations may be short-lived without external stabilizing factors.sup.9-19. Here we performed microcosm experiments with a planktonic predator-prey system and repeatedly observed oscillatory time series of unprecedented length that persisted for up to around 50 cycles or approximately 300 predator generations. The dominant type of dynamics was characterized by regular, coherent oscillations with a nearly constant predator-prey phase difference. Despite constant experimental conditions, we also observed shorter episodes of irregular, non-coherent oscillations without any significant phase relationship. However, the predator-prey system showed a strong tendency to return to the dominant dynamical regime with a defined phase relationship. A mathematical model suggests that stochasticity is probably responsible for the reversible shift from coherent to non-coherent oscillations, a notion that was supported by experiments with external forcing by pulsed nutrient supply. Our findings empirically demonstrate the potential for infinite persistence of predator and prey populations in a cyclic dynamic regime that shows resilience in the presence of stochastic events. The potential for infinite persistence of planktonic predator and prey cycles is experimentally demonstrated and these cycles show resilience in the presence of stochastic events., Author(s): Bernd Blasius [sup.1] [sup.2] , Lars Rudolf [sup.3] , Guntram Weithoff [sup.4] [sup.5] , Ursula Gaedke [sup.4] [sup.5] , Gregor F. Fussmann [sup.6] Author Affiliations: (1) Institute for Chemistry [...]

Published
2020
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27. Functional diversity buffers the effects of a pulse perturbation on the dynamics of tritrophic food webs

Author

Wojcik, Laurie Anne, Ceulemans, Ruben, and Gaedke, Ursula

Subjects
Ecology, regime shift, tritrophic food web, robustness, functional diversity, ddc:570, nutrient spike, ddc:500, pulse perturbation, human activities, Research Articles, Institut für Biochemie und Biologie, QH540-549.5, Research Article, 570 Biowissenschaften, Biologie
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., The response of a tritrophic food web to a nutrient pulse depends (1) on the amount of extra nutrients added (the perturbation size Np ) and (2) on the moment at which the perturbation is applied, and in particular on top‐down regulatory processes. Importantly, the system response depends (3) on the functional diversity present. Functional diversity has positive or context‐dependent direct effects (in green) and indirect effects (in violet)—by increasing the probability of the system to be on the ecologically desirable high‐production attractor (HP)—on the robustness, that is, the resistance, resilience, and elasticity.

Published
2021

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