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Phylogéographie et évolution moléculaire comparée d'arbres forestiers à l'aide des marqueurs chloroplastiques

Abstract : Biodiversity can be measured at several levels. In ecology, biodiversity is often described at the species level whereas geneticists work at the levels of populations or individuals. It would be of great interest to obtain measures that combine both levels in order to select the most appropriate conservation strategy. Nevertheless few studies have integrated the analysis of the genetic diversity at the multispecies level. The objective of this thesis was to contribute to a European synthesis dealing with genetic variation of temperate deciduous trees to be analysed simultaneously with chloroplast markers. Three approaches have been followed. (i) The phylogeography of three species (the ivy, the horbeam and the oak) was studied. Several methods were used and compared to analyse the geographic structure of diversity. In addition, one chloroplast fragment (trnK intron) was sequenced in order to obtain intraspecific phylogenies. Location of refugia and of colonisation routes and the capacity to maintain diversity differ among species. (ii) A set of consensus primer pairs was designed in order to cover all of the large single copy of the chloroplast genome. This set was studied over the 20 species of the European project. This allowed us to initiate a study on the size variation of the chloroplast genome based on the comparative method. We first confirrned that the size variation of the amplified fragments was due to the percentage of non-coding sequences in the amplified fragment. We showed that the origin of the cpDNA size evolution is not only the result of phylogenetic constraints but also of intrinsic evolutionary properties of the cbloroplast genome. (iii) We compared the nucleotide diversity of the trnK sequence (containing the matK exon) across several tree species. We found at both intra- and interspecific level a majority of synonymous substitutions in the matK exon, but non synonymous mutations seem overrepresented at the intraspecific level. Finally it appears that the intraspecific nucleotide diversity is not correlated wîth the sequence evolutionary rate.
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http://docnum.univ-lorraine.fr/prive/SCD_T_2002_0002_GRIVET.pdf
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Submitted on : Thursday, March 29, 2018 - 10:41:06 AM
Last modification on : Monday, October 19, 2020 - 11:25:52 AM

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Delphine Grivet. Phylogéographie et évolution moléculaire comparée d'arbres forestiers à l'aide des marqueurs chloroplastiques. Sciences agricoles. Université Henri Poincaré - Nancy 1, 2002. Français. ⟨NNT : 2002NAN10002⟩. ⟨tel-01746602⟩

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