Genetic structure of the common sole Solea vulgaris at different geographic scales

The genetic structure of the flatfish #Solea vulgaris was investigated on several spatial scales and at the temporal level through analysis of electrophoretic variation at 8 to 12 polymorphic enzyme loci. No differentiation was apparent at the temporal scale. Some differentiation was detected at and above the regional scale. Isolation by distance was evidenced by the significant correlation between genetic and geographic distances, and by the consistency of the results of multiple-locus correspondence analysis with geographic sampling patterns. The analysis suggested that the geographic unit of population structure (i.e. a geographical area corresponding to a panmictic or nearly panmictic population) lies within a radius of the order of 100 km. The isolation-by-distance pattern in #S. vulgaris contrasted with the known genetic structures of other flatfish species of the northeastern Atlantic and Mediterranean in a way that may be related to the range of their respective temperature tolerances for eggs and larvae. (Résumé d'auteur

Génétique des populations de Beryx splendens de la zone économique de la Nouvelle-Calédonie : distribution des haplotypes du gène du cytochrome b de l'ADN mitochondrial et analyse phylogénétique de leurs séquences

La délimitation géographique des populations, établie sur les bases biologiques, est nécessaire à toute gestion rationnelle des pêcheries. Tel est le cas pour #Beryx splendens, ressource pour laquelle la mise en évidence de différentes populations dans la zone économique (ZE) de Nouvelle-Calédonie serait essentielle pour en éviter la surexploitation. L'ADN mitochondrial a été choisi comme marqueur génétique de la structure géographique de #B. splendens sur les monts sous-marins de la ZE de Nouvelle-Calédonie. (D'après résumé d'auteur

Structures génétiques comparées de trois espèces de rongeurs africains du genre Mastomys au Sénégal

Dans le cadre d'une étude globale de la biologie des populations du genre #Mastomys au Sénégal, cette étude présente la méthode d'analyse des protéines par électrophorèse. Cette méthode permet de caractériser les espèces en présence et d'appréhender les structurations génétiques propres à chaque espèces. L'analyse a porté sur trois espèces du genre #Mastomys au Sénéga

Genetic hitchhiking in a subdivided population of Mytilus edulis

<p>Abstract</p> <p>Background</p> <p>Few models of genetic hitchhiking in subdivided populations have been developed and the rarity of empirical examples is even more striking. We here provide evidences of genetic hitchhiking in a subdivided population of the marine mussel <it>Mytilus edulis</it>. In the Bay of Biscay (France), a patch of <it>M. edulis </it>populations happens to be separated from its North Sea conspecifics by a wide region occupied only by the sister species <it>M. galloprovincialis</it>. Although genetic differentiation between the two <it>M. edulis </it>regions is largely non-significant at ten marker loci (average F_ST~0.007), a strong genetic differentiation is observed at a single locus (F_ST= 0.25). We validated the outlier status of this locus, and analysed DNA sequence polymorphism in order to identify the nature of the selection responsible for the unusual differentiation.</p> <p>Results</p> <p>We first showed that introgression of <it>M. galloprovincialis </it>alleles was very weak in both populations and did not significantly affect their differentiation. Secondly, we observed the genetic signature of a selective sweep within both <it>M. edulis </it>populations in the form of a star-shaped clade of alleles. This clade was nearly fixed in the North Sea and was segregating at a moderate frequency in the Bay of Biscay, explaining their genetic differentiation. Incomplete fixation reveals that selection was not direct on the locus but that the studied sequence recombined with a positively selected allele at a linked locus while it was on its way to fixation. Finally, using a deterministic model we showed that the wave of advance of a favourable allele at a linked locus, when crossing a strong enough barrier to gene flow, generates a step in neutral allele frequencies comparable to the step observed between the two <it>M. edulis </it>populations at the outlier locus. In our case, the position of the barrier is now materialised by a large patch of heterospecific <it>M. galloprovincialis </it>populations.</p> <p>Conclusion</p> <p>High F_SToutlier loci are usually interpreted as being the consequence of ongoing divergent local adaptation. Combining models and data we show that among-population differentiation can also dramatically increase following a selective sweep in a structured population. Our study illustrates how a striking geographical pattern of neutral diversity can emerge from past indirect hitchhiking selection in a structured population.</p> <p>Note</p> <p>Nucleotide sequences reported in this paper are available in the GenBank™ database under the accession numbers <ext-link ext-link-type="gen" ext-link-id="EU684165">EU684165</ext-link> – <ext-link ext-link-type="gen" ext-link-id="EU684228">EU684228</ext-link>.</p