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Variation des traits le long des gradients environnementaux : rôle de l'intégration phénotypique et de la variabilité au sein des clades

Abstract : The response of traits to the environment has been studied mainly at the level of trait means within and across species and lineages and has recently been extended to intraspecific trait variability. However, traits may respond to the constraints of a given environment also in terms of (i) increased mutual determination of traits within individuals and populations, i.e. increased phenotypic integration, and (ii) decreased variation of traits within entire phylogenetic lineages. Here we tested: (i) the effects of abiotic and biotic environments on phenotypic integration within sub-Antarctic plant species and the ecological and biogeographic consequences of a strong phenotypic integration, and (ii) the effects of abiotic and biotic environments on the phenotypic variability realized within Angiosperm genera of Central Europe. Regarding the first aspect, we found that phenotypic integration is higher under stressful abiotic conditions. The increase in phenotypic integration occurs at small spatial scales and may constrain the large scale flexibility of growth and reproductive strategies. We also found that strong phenotypic and environmental integration may contribute to endemism of some sub-Antarctic species, probably through a long-term specialization of these species to their habitat. Regarding the second aspect, we found that phenotypic variability realized within genera of Central Europe is higher under intermediate abiotic conditions, reflecting increased independence of traits from the abiotic environment. We also found that the number of coexisting species is highly conserved within genera. Intermediate levels of coexistence tend to correspond to both intermediate positions along abiotic gradients and to highest levels of variability of certain traits. This suggests a role of numerous but still predictable biotic interactions for the maintenance (or evolution) of high levels of trait variability within clades. Overall, the results of both aspects suggest the capacity of species to respond to environmental variations may be strongly constrained at the level of both individual phenotypes and entire clades, notably under abiotically but also biotically extreme environments.
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Submitted on : Friday, April 22, 2011 - 4:42:59 PM
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Marie Hermant. Variation des traits le long des gradients environnementaux : rôle de l'intégration phénotypique et de la variabilité au sein des clades. Ecologie, Environnement. Université Rennes 1, 2011. Français. ⟨tel-00588294⟩

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