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Master Thesis

Entre théorie trophique et données macroécologiques : relations allométriques et réponse fonctionnelle

Abstract : This manuscript addresses an essential question in trophic ecology: how to explain the cross-ecosystem variation in the strength of (top-down) control of preys by predators. By confronting macroecological data and mathematical models, several theoretical assumptions are tested. In the literature, allometric relations and functional response are claimed to be key components of trophic control. Scaling laws have been proposed between metabolism (m) and body mass (w) in the form m ~wb with b ∈ [-0.33, -0.25], and we find similar laws for predator- prey ratios within a taxonomic class, but not between classes. Species strategies and habitat do not appear to modify these laws. Functional response has been estimated in many studies focusing on particular systems, and using several mathematical expressions. The best-fit model for our macroecological data exhibits an unusual power-law scaling, the square root of the product of prey and predator biomasses and the prey metabolism. This agrees with expressions proposed for predators hunting in groups and preys living in herds. Comparing this functional response to prey production yields an estimate of the strength of top-down control, which does not seem to be constrained by metabolism or body mass. According to theory, a more precise estimate of top-down control strength involves the intensity of self-regulation, which is unknown for most populations in our dataset. These exploratory results, based on observational data, should be confronted to meta-analyses of experimental data, and expanded using larger datasets.
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Master Thesis
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Submitted on : Friday, December 20, 2019 - 11:27:51 AM
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  • HAL Id : dumas-02421042, version 1



Laurie Wojcik. Entre théorie trophique et données macroécologiques : relations allométriques et réponse fonctionnelle. Sciences du Vivant [q-bio]. 2019. ⟨dumas-02421042⟩



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