Archives Thèses, HDR

Avis de Soutenance

Eva LIEVENS

Soutiendra publiquement ses travaux de thèse intitulés

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

 

Soutenance prévue le lundi 12 décembre 2016 à 15h

Lieu : L'amphi des plantes de l'IRD


Composition du jury proposé

Mme Ellen Decaestecker, Associate Professor, KU Leuven – Leuven Rapporteur

Mme Meghan Duffy, Associate Professor, University of Michigan – USA Rapporteur

Mme Alison Duncan, CR, ISEM – Montpellier Examinateur

M. Thierry Rigaud, DR, Université de Bourgogne – Dijon Examinateur

M. Yannis Michalakis, DR, MIVEGEC – Montpellier Co-directeur de thèse

M. Thomas Lenormand, DR, CEFE – Montpellier Directeur de thèse

 

Résumé:

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.

Mots-clés: reproductive interference, sex allocation, mate guarding, parasite specialization, parasite seasonality, virulence, trade-offs, maladaptation, interspecific interactions