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Thèse Année : 2014

Phenotypic changes in invasive species: roles of rapid adaptation and historical factors

Changements phénotypiques chez les espèces invasives : rôles de l’adaptation rapide et des facteurs historiques

Résumé

Recently, there has been a growing interest for rapid evolution and its potential role in ecological processes. For example, it has been hypothesized that rapid adaptation is a factor favoring the establishment of invasive species in new environments. If this hypothesis is true, it could have implications in the management and prevention of biological invasions. In vertebrates, lots of studies report cases of rapid phenotypic changes in invasive species following their introduction in a novel environment. However, because of the difficulties of directly testing for adaptation, very few of them were able to prove that these phenotypic changes result from rapid adaptation. In this thesis, we were thus interested in assessing whether rapid adaptation can explain phenotypic changes observed in recently introduced populations. Instead of directly testing for adaptation, we tested for alternative hypotheses, which are easier to investigate. Indeed, a phenotypic difference observed between populations established in different environments can be caused by natural selection but also by phenotypic plasticity, by a different phylogenetic origin and by stochastic evolution (i.e. stochastic changes in allele frequencies in a population as the result of demographic processes such as founder effects and bottlenecks). Here, we studied two successful invasive bird species introduced in several kinds of environments. We described the morphology of individuals in these populations, and tested for the effects of historical factors (i.e. phylogenetic origin and recent demographic history) to explain morphological differences observed between populations. In both species, our results show that stochastic evolution resulting of recent demographic history is likely to be the cause of the morphological differences observed. This was true for all the cases we studied except one. In this last case, neither a difference in phylogenetic origin, nor stochastic evolution could explain de phenotypic differences observed between two environments. It is therefore possible that rapid adaptation occurred in this case but the hypothesis of phenotypic plasticity remains to be tested. In conclusion, with this work we highlighted that recent demographic processes can have an important role in causing morphological differentiation in invasive species. This role was probably underestimated in studies on rapid adaptation and should be taken into account in the future. We also showed that the comparative approach we used can allow identifying possible cases of rapid adaptation by first rejecting alternative hypotheses.
Évolution morphologique rapide en lien avec l'histoire démographique chez deux espèces invasives.
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Dates et versions

tel-01230866 , version 1 (19-11-2015)

Identifiants

  • HAL Id : tel-01230866 , version 1

Citer

Ariane Le Gros. Phenotypic changes in invasive species: roles of rapid adaptation and historical factors. Ecology, environment. Université Paris Diderot, 2014. English. ⟨NNT : ⟩. ⟨tel-01230866⟩
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