Dataset Information

Exploring neutral and adaptive processes in expanding populations of gilthead sea bream, Sparus aurata L., in the North-East Atlantic.

ABSTRACT: Recent studies in empirical population genetics have highlighted the importance of taking into account both neutral and adaptive genetic variation in characterizing microevolutionary dynamics. Here, we explore the genetic population structure and the footprints of selection in four populations of the warm-temperate coastal fish, the gilthead sea bream (Sparus aurata), whose recent northward expansion has been linked to climate change. Samples were collected at four Atlantic locations, including Spain, Portugal, France and the South of Ireland, and genetically assayed using a suite of species-specific markers, including 15 putatively neutral microsatellites and 23 expressed sequence tag-linked markers, as well as a portion of the mitochondrial DNA (mtDNA) control region. Two of the putatively neutral markers, Bld-10 and Ad-10, bore signatures of strong directional selection, particularly in the newly established Irish population, although the potential 'surfing effect' of rare alleles at the edge of the expansion front was also considered. Analyses after the removal of these loci suggest low but significant population structure likely affected by some degree of gene flow counteracting random genetic drift. No signal of historic divergence was detected at mtDNA. BLAST searches conducted with all 38 markers used failed to identify specific genomic regions associated to adaptive functions. However, the availability of genomic resources for this commercially valuable species is rapidly increasing, bringing us closer to the understanding of the interplay between selective and neutral evolutionary forces, shaping population divergence of an expanding species in a heterogeneous milieu.

SUBMITTER: Coscia I

PROVIDER: S-EPMC3331784 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature

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Exploring neutral and adaptive processes in expanding populations of gilthead sea bream, Sparus aurata L., in the North-East Atlantic.

Coscia I I Vogiatzi E E Kotoulas G G Tsigenopoulos C S CS Mariani S S

Heredity 20111130 5

Recent studies in empirical population genetics have highlighted the importance of taking into account both neutral and adaptive genetic variation in characterizing microevolutionary dynamics. Here, we explore the genetic population structure and the footprints of selection in four populations of the warm-temperate coastal fish, the gilthead sea bream (Sparus aurata), whose recent northward expansion has been linked to climate change. Samples were collected at four Atlantic locations, including ...[more]

PMID: 22126850

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Project description:Gilthead sea bream (Sparus aurata) is a species of paramount importance to the Mediterranean aquaculture industry, with an annual production exceeding 140,000 metric tonnes. Pasteurellosis due to the Gram-negative bacterium Photobacterium damselae subsp. piscicida (Phdp) causes significant mortality, especially during larval and juvenile stages, and poses a serious threat to bream production. Selective breeding for improved resistance to pasteurellosis is a promising avenue for disease control, and the use of genetic markers to predict breeding values can improve the accuracy of selection, and allow accurate calculation of estimated breeding values (EBV) of non-challenged animals. In the current study, a population of 825 sea bream juveniles, originating from a factorial cross between 67 broodfish (32 sires; 35 dams), were challenged by 30 min immersion with 1 × 10(5) CFU virulent Phdp. Mortalities and survivors were recorded and sampled for genotyping by sequencing. The 2b-RAD sequencing approach was used to generate genome-wide SNP genotypes for all samples. A high-density linkage map containing 12,085 SNPs grouped into 24 linkage groups (consistent with the karyotype) was constructed. The heritability of surviving days (censored data) was 0.22 (95% highest density interval: 0.11-0.36) and 0.28 (95% highest density interval: 0.17-0.4) using the pedigree and the genomic relationship matrix respectively. A genome wide association study did not reveal individual SNPs significantly associated with resistance at a genome wide significance level. Genomic prediction approaches were tested to investigate the potential of the SNPs obtained by 2bRAD for estimating breeding values for resistance. The accuracy of the genomic prediction models (r = 0.38 - 0.46) outperformed the traditional BLUP approach based on pedigree records (r = 0.30). Overall results suggest that major quantitative trait loci (QTL) affecting resistance to pasteurellosis were not present in this population, but highlight the effectiveness of 2b-RAD genotyping by sequencing for genomic selection in a mass spawning fish species.

Project description:BackgroundPhotobacteriosis is an infectious disease developed by a Gram-negative bacterium Photobacterium damselae subsp. piscicida (Phdp), which may cause high mortalities (90-100%) in sea bream. Selection and breeding for resistance against infectious diseases is a highly valuable tool to help prevent or diminish disease outbreaks, and currently available advanced selection methods with the application of genomic information could improve the response to selection. An experimental group of sea bream juveniles was derived from a Ferme Marine de Douhet (FMD, Oléron Island, France) selected line using ~?109 parents (~?25 females and 84 males). This group of 1187 individuals represented 177 full-sib families with 1-49 sibs per family, which were challenged with virulent Phdp for a duration of 18 days, and mortalities were recorded within this duration. Tissue samples were collected from the parents and the recorded offspring for DNA extraction, library preparation using 2b-RAD and genotyping by sequencing. Genotypic data was used to develop a linkage map, genome wide association analysis and for the estimation of breeding values.ResultsThe analysis of genetic variation for resistance against Phdp revealed moderate genomic heritability with estimates of ~?0.32. A genome-wide association analysis revealed a quantitative trait locus (QTL) including 11 SNPs at linkage group 17 presenting significant association to the trait with p-value crossing genome-wide Bonferroni corrected threshold P???2.22e-06. The proportion total genetic variance explained by the single top most significant SNP was ranging from 13.28-16.14% depending on the method used to compute the variance. The accuracies of predicting breeding values obtained using genomic vs. pedigree information displayed 19-24% increase when using genomic information.ConclusionThe current study demonstrates that SNPs-based genotyping of a sea bream population with 2b-RAD approach is effective at capturing the genetic variation for resistance against Phdp. Prediction accuracies obtained using genomic information were significantly higher than the accuracies obtained using pedigree information which highlights the importance and potential of genomic selection in commercial breeding programs.

Dataset Information

Exploring neutral and adaptive processes in expanding populations of gilthead sea bream, Sparus aurata L., in the North-East Atlantic.

Publications

Exploring neutral and adaptive processes in expanding populations of gilthead sea bream, Sparus aurata L., in the North-East Atlantic.

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