Population genomics to detect local adaptation: application to Bti resistance monitoring in mosquitoes at a regional scale

Abstract : Identification of genes involved in local adaptation is particularly challenging in species functioning as a network of inter-connected populations undergoing frequent extinction-recolonisation, because populations are submitted to contrasted evolutionary pressures. Using AFLP markers, population genetic structure of the mosquito Aedes rusticus was analyzed in five geographical areas of the French Rhône-Alpes region, including sites treated with the bio-insecticide Bacillus thuringiensis subsp. israelensis (Bti) for more than 15 years. Most of the genetic variability was found within populations, with no significant variation among geographical areas, although variation among populations within areas was significant. Pairwise FST values were significant and no isolation-by-distance was observed, suggesting a metapopulation structure in this species at the regional scale. Bti treatment had no effect on genetic structure, and within-population diversity levels were not significantly higher in non-treated compared with treated sites, suggesting that these are rapidly re-colonized by a diversified population of migrants after Bti treatment. However, signatures of positive selection associated with Bti treatment were detected for five loci, even though standard toxicological bioassays performed on field-collected larvae showed no significant difference in mortality between Bti-treated and non-treated sites. The absence of resistant phenotypes may result from the polygenic basis of resistance mechanisms to Bti, together with a high resistance cost measured in a laboratory selected mosquito strain. We also showed that selected mosquitoes are only moderately resistant to the full commercial Bti mixture, but show high levels of resistance to separate Bti toxins. This suggests that monitoring resistance in field populations should require evaluating mosquito resistance to individual Bti toxins, rather than to full commercial Bti mixture. We propose new methods for monitoring Bti resistance evolution in mosquito populations, in order to detect resistance at the very early steps of its appearance, when bioassays using Bti fail to detect resistance.
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Communication dans un congrès
Towards a multi-scale approach for improving pest management. Methods for tracking movement and dispersal of insect pest individuals and populations, Oct 2011, Montpellier, France
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Contributeur : Thierry Brévault <>
Soumis le : lundi 28 novembre 2011 - 15:38:44
Dernière modification le : jeudi 11 janvier 2018 - 06:15:58

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Laurence Després, Guillaume Tetreau, Margot Paris, Aurélie Bonin. Population genomics to detect local adaptation: application to Bti resistance monitoring in mosquitoes at a regional scale. Towards a multi-scale approach for improving pest management. Methods for tracking movement and dispersal of insect pest individuals and populations, Oct 2011, Montpellier, France. 〈cirad-00645752〉

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