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Virginie ROUGERON soutiendra son HDR sur

Adaptation évolutive des systèmes hôtes-parasites

 

le 09 février 2017 à 14h00 dans l’amphithéâtre des Plantes du Centre IRD de Montpellier

 

 

Boris Makanga soutiendra sa thèse le 16 décembre 2016 à 14h, dans les salles 151-161 de l'IRD. Le sujet concerne :

Ecologie de la transmission des Plasmodium simiens au Gabon

 

 

 

Eva LIEVENS soutiendra sa thèse intitulée,

Biotic challenges for extremophiles: reproductive interference and parasite specialization in Artemia

 

Le 12 décembre 2016 à 15:00, dans l’amphi des plantes à l’IRD.

 

Supervisors: Yannis Michalakis & Thomas Lenormand

Jury: Ellen Decaestecker, Meghan Duffy, Alison Duncan, Thierry Rigaud

Abstract: The challenges posed by biotic factors – interactions with competitors, parasites, etc. – play a large role in the evolution of populations, but are generally difficult to study. In this work, we used the Artemia system in the hypersaline salterns of Aigues-Mortes, France, to study the character and evolution of several interspecific interactions. The system is eminently suited to such studies: it is simple, containing two Artemia species, three highly prevalent parasites (one helminth and two microsporidians), and various microbiota; and many of its interactions are newly-established, because one of the Artemia species is invasive. We studied two types of interactions. First, the presence and evolution of reproductive interference between the native and invasive Artemia species. We found that the invasive Artemia species, which is sexual, undergoes severe interference in sex allocation when in the presence of the native, asexual Artemia, but no interference in mate guarding. Second, the evolution of parasite specialization in two microsporidian parasites infecting the Artemia species. Using field data, experimental infections, and experimental evolution, we investigated the state, causes, and consequences of specialization in the microsporidians. Results consistently indicated that the microsporidians are specialized for one host species, despite being able to complete their life cycle in either host. This specialization appears to be imposed by the precise toolkits needed to exploit each host species; in the non-specialized hosts, these triggered suboptimal exploitation, maladaptive virulence, and immunopathology. Overall, these studies suggest that the biotic factors acting on Artemia impose strong selection pressures, to which they cannot always respond easily. The importance of biotic factors in a system which is otherwise dominated by extreme abiotic conditions underlines the importance of species interactions in shaping evolution.