Soutenance de thèse de Louraine Salabao
Quartier Agora - allée du 6-Août 17
4000 Liège Voir la carte
Le mardi 12 décembre 2023, Louraine SALABAO présentera l'examen en vue de l’obtention du grade académique de Docteur en Sciences (Collège de doctorat en Biologie des organismes et écologie) sous la direction de Bruno FREDERICH et Isabelle SCHON (Cotutelle avec l’Universiteit Hasselt).
Cette épreuve consistera en la défense publique d’une dissertation intitulée :
« Evolution and diversification of Amphipoda in the polar regions: the case study of Eusirus genus ».
The past major climate changes have disrupted life in the polar regions and triggered different responses in marine organisms. Confronted now with fast-paced environmental changes such as global warming, understanding the adaptations and patterns of diversification in these regions with extreme environmental conditions can help to predict their possible response to future climate change. By combining molecular, morphological, and ecological data, this study aims to understand the genetic adaptations and the evolutionary processes that shaped the current diversity of the Eusirus amphipods in the Arctic and Southern Oceans. First, three novel complete Antarctic mitogenomes were assembled and annotated and showed distinct features such as a lower AT-richness in the whole mitogenomes, negative GC-skews on both strands of protein coding genes, and unique gene rearrangements. Second, molecular signatures of cold adaptations were highlighted by comparing different mitogenomic features of amphipods from cold, temperate, and warm regions and showed that amphipods living in cold environment possessed mitogenomes with low proportions of charged amino acids and high, average ratios of non-synonymous to synonymous substitutions (ω). Third, new phylogenetic reconstructions of Eusirus and a novel dated tree were produced and strongly supported the monophyly of the Antarctic clade whereas Arctic Eusirus had a polyphyletic origin and an older mean age compared to the Antarctic Eusirus. Finally, the integration of phylogenetic information, phenotypic and ecological data identified two different evolutionary patterns of Eusirus in the polar oceans. A high rate of lineage diversification coupled with low rate of morphological evolution supported a non-adaptive radiation scenario in the Antarctic clade. The contrasting slower diversification rates observed in the Arctic Eusirus lineages could be explained by higher gene flow and higher extinction rates. Moreover, high morphological and ecological diversity in Arctic Eusirus could be associated to their polyphyletic origin and their older evolutionary age.
Le Jury sera composé de :
M. J.-C. PLUMIER (Président), Mmes et MM. A. DETTAI (Museum National d’Histoire Naturelle, Paris), B. FREDERICH (Promoteur), N. KMENTOVA (Universiteit Hasselt), G. LEPOINT (Secrétaire), I. SCHON (IRSNB) (Promotrice), M. VERHEYE (KULeuven).