The influence of environmental changes and individual trait variability (phenotypic plasticity) on biodiversity and ecosystem stability

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Diversity is a major precondition for the adaptive reaction to environmental change. Biodiversity at all levels (genetic, species, interactions) is crucial for ecosystem function and stability as higher biodiversity means redundancy which stabilizes ecosystems because extinct species/genotypes can be replaced. In addition, the presence of individual trait variation and/or phenotypic plasticity can stabilize population fluctuations and thereby prevent extinction. Recently however, biodiversity is declining at a rapid rate while environmental disturbances and large scale changes are increasing in frequency and severity.We are therefore interested in what influence the presence of individual trait variation has on the genetic diversity of a population and a predator-prey interaction and how this might influence ecosystem function and stability. Two hypotheses will be considered: (I) Phenotypic plasticity (trait variation) might increase the biodiversity of ecosystems because it allows for a better niche use.(II) Phenotypic plasticity (trait variation) might decrease biodiversity because it enables the plastic organism to exploit several niches rather than allowing a specialization of different genotypes. In addition, we will challenge this system by testing how environmental (abiotic) stress influences ecosystem stability.We will use the model predator-prey system Daphnia pulex and its predator Chaoborus larvae in a two-fold approach: 1) Mesocosm experiments will be set up that will test the influence of stressors (predation, high temperature and elevated levels of CO2) on the genetic diversity of an artificial Daphnia population. The Daphnia population will consist of 10 different clones with different reaction norms in their phenotypic response to predation. Daphnia populations will be exposed to one biotic stressor (invertebrate predation) and two abiotic stressors that are direct effects of anthropogenic disturbances (high temperature and elevated levels of CO2). We will monitor the clonal diversity of the prey species as well as the performance of the predator species (Chaoborus larvae). 2) A modeling approach will provide us with predictions about feedback loops on prey genotypic diversity and phenotype/genotype interaction and predator and prey survival capacities under different environmental conditions. With this integrative approach we will get a deeper insight into the effect of individual trait variation and phenotypic plasticity on the clonal diversity of populations as well as an estimate of how clonal diversity influences an ecosystem’s function and stability.