Etude multi-locus des pressions évolutives s'exerçant sur les bivalves marins en situation d'hybridation : cas des moules hydrothermales du genre Bathymodiolus des dorsales médio-Atlantique et est-Pacifique

Abstract : This work aimed, through a multi-locus multi-species study of gene convalescence, at understanding the modes of speciation and evolutionary mechanisms acting on Mytilid bivalves (genus Bathymodiolus) submitted to the extreme environmental conditions that prevail in the deep sea. Firstly, the phylogeny of all species belonging to the family Bathymodiolinae was studied by the dual use of a nuclear and a mitochondrial marker. In a second part, a multilocus approach was carried out on a hybrid zone existing on the Mid Atlantic Ridge to unravel the genetic structure and measure the level of reciprocal introgression between Bathymodiolus azoricus and B. puteoserpentis. A Bayesian approach (through the implementation of the Isolation with Migration IMa software) allowed us to measure the intensity and the directionality of residual gene flow between the two species, this varying among genes and pointing towards a secondary contact after a period of isolation rather than a continuous differentiation. Another study on the East-Pacific Ridge has allowed us to describe a new hybrid zone between the local species B. thermophilus and a new species localised at 37°S. Certain genes having demonstrated pecularities in their evolutionary histories have been subjected to specific scrutiny, evidencing purifying selection acting on an intron of the gene Elongation Factor EF1α, or a relaxation of selective pressures on certain copies of the Heat Shock Protein HSP70. Our study underlines the fact that the genetic structuring of hydrothermal species such as deep-sea mussels is ascribable primarily to geological conditions (volcanism, tectonics and transforming faults) and that this results on the long term in allopatric speciation. We also confirm that marine bivalves, including the deep-sea ones, are among the more polymorphic species on earth and that this polymorphism contains many slighly deleterious mutations.
Document type :
Theses
Complete list of metadatas

https://hal.sorbonne-universite.fr/tel-01112819
Contributor : Novelenn Louise <>
Submitted on : Tuesday, February 3, 2015 - 4:43:26 PM
Last modification on : Friday, May 24, 2019 - 5:00:05 PM
Long-term archiving on: Saturday, September 12, 2015 - 8:16:47 AM

Identifiers

  • HAL Id : tel-01112819, version 1

Citation

Baptiste Faure. Etude multi-locus des pressions évolutives s'exerçant sur les bivalves marins en situation d'hybridation : cas des moules hydrothermales du genre Bathymodiolus des dorsales médio-Atlantique et est-Pacifique. Ecosystèmes. Montpellier II, 2008. Français. ⟨tel-01112819⟩

Share

Metrics

Record views

342

Files downloads

3959