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ORIGIN, ADAPTATION AND EVOLUTION OF PLASMODIUM FALCIPARUM IN A NEW ENVIRONMENT : THE ANALYSIS OF AN INVASIVE SPECIES

 

Erhan YALCINDAG

le Jeudi 08 Décembre 2011 à 14:00 dans l'amphithéàtre du bàtiment des plantes, au Centre IRD de Montpellier.

 

Le jury sera composé de :
 
- Tatiana Giraud (Rapportrice)
 
- André Theron (Rapporteur)
 
- Carlo Severini (Examinateur)
 
- Emmanuel Douzery (Examinateur)
 
- François Renaud (Co-directeur de thèse)
 
- Franck Prugnolle (Directeur de thèse)
 
 

 

 

Abstract: The evolutionary biology allows to understand and to trace the origin of species or populations, to understand their dispersions in different areas and analyse the differentiation from these evolutions. Biological invasions and invasive species in general, are good models to study and understand the adaptation to new environments. Plasmodium falciparum, a protozoan parasite, agent of malaria, invaded new host populations and new vector species several times. The objectives of this thesis were: (i) to analyse the introduction, origin and distribution of P. falciparum in radically different environments. a new geographical area (South America) and a new host species (in monkeys); and (ii) to identify genes potentially involved in the adaptation to these new environments. I addressed these questions using different approaches, including population genetic, phylogeographic and phylogenetic analyses. Our results demonstrate for the first time that P. falciparum has been introduced by humans at least twice in South America from Africa. This thesis has also demonstrated that this parasite naturally circulates in nonhuman primates in Africa. In addition, an analysis of the patterns of selection on candidate genes playing a role in the invasion of erythrocytes by the parasite was performed to determine if adaptive evolutions occured on these specific genes in these new environments. Overall, our results demonstrate that P. falciparum can be considered an invasive species and that is parasite is not specific to humans. All of our work allowed us to advance in the knowledge of the biological model in terms of strategy of emergence or reemergence in different environments. Our results highlight the changes that have taken place in the geographical distribution and during the emergence a new host species used by P. falciparum.

 

Keywords: Biological invasion, invasive species, parasite, origin, adaptation, selection, emerging infectious diseases, Plasmodium falciparum, South America, population genetics, phylogeography, molecular markers, monkeys.