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Effects of intraspecific variability of invertebrates' phenotype on litter decomposition

Abstract : Intraspecific variability of individuals' phenotype is at the root of natural selection, but remains poorly evaluated from the ecosystem functioning perspective. My research has focused on measuring individual and population differences in phenotypic traits of invertebrates involved in detrital food webs, as well as evaluating their impact on litter decomposition. First, I showed that intraspecific differences of litter consumption rate is high compared to the interspecific differences measured experimentally on a sample of 10 terrestrial and aquatic detritivore species. Another laboratory study revealed that litter consumption rate differences between individuals of a same population can be explained by behavioral and energetic traits. Oppositely, body size of individuals proved to be less effective in explaining inter-individual variability of litter consumption rates. Traits of predator invertebrates can also act on litter decomposition indirectly through interactions with detritivores. An in situ experiment has shown that predator individuals with different phenotypes can have opposite effects on decomposition. Trophic cascade variability was explained by sex and a lifestyle index, defined by a combination of behavioral and life history traits. Finally, I validated the hypothesis that the origin of predator populations sampled along a latitudinal gradient in Europe modulates the response of litter decomposition to global warming. All my work highlights the underestimated role of intraspecific variability of phenotype in Ecology. Individual, rather than species, should be the basic unit to better understand the biotic control of ecosystem functioning and to predict the ecological consequences of environmental changes.
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Thibaut Rota. Effects of intraspecific variability of invertebrates' phenotype on litter decomposition. Global Changes. Université Paul Sabatier - Toulouse III, 2018. English. ⟨NNT : 2018TOU30309⟩. ⟨tel-02080487v2⟩

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