Genomic and ecological bases of aphid adaptation in the context of fruit tree domestication

Genomic and ecological bases of aphid adaptation in the context of fruit tree domestication

Soutenance de thèse
 06/11/2023
 14:00:00
 Sergio Gabriel Olvera Vazquez
 IDEEV - Salle Rosalind Franklin

Understanding local adaptation processes in host-parasite interactions helps to tackle pressing issues, such as how environmental changes alter the emergence of parasites, leading to host extinction. During my Ph.D., we investigated whether adaptation occurred during the recent colonization of the cultivated apple by Dysaphis plantaginea in Europe and its associated genomic bases. First, we studied genes involved in aphid adaptation to their host at a macroevolutionary scale. We showed a higher evolutionary rate in an aphid subfamily driven by gene expansion and contraction with functions related to aphid adaptation to their hosts. We showed low synteny of olfactory receptors (OR) and gustatory receptors (GR) genes, evolving in tandem repeats following the birth-death model and under purifying selection. Transposable elements (TEs) did not have a role in the GR and OR gene evolution. However, we found species-specific TE dynamics, with major TEs burst in aphid infesting fruit trees. We also used a microevolutionary lens and reconstructed the colonization history of D. plantaginea on the cultivated apple using microsatellite markers. We detected five populations in the US, Morocco, Western and Eastern Europe, and Spain. Populations showed weak genetic differentiation and high genetic diversity, except in Morocco and North America, likely due to recent colonization events there. I used single nucleotide polymorphisms (SNPs) to investigate genomic patterns of (local) adaptation in D. plantaginea and its two sister species, Dysaphis devecta and Dysaphis pyri. The three species formed distinct genetic groups, and D. plantaginea showed four distinct populations in North America, Israel, Morocco/Spain, and the rest of the European countries. I present preliminary results of genome scans in the six genetic groups detected before, which revealed candidate outlier SNPs for adaptation, but further investigations are needed. Lastly, we studied the ecological bases of D. plantaginea local adaptation using an experimental approach. Our preliminary results suggest local maladaptation of the French aphid population while global adaptation of the Spanish population. Further analysis is needed to clarify these patterns of adaptation. The results of this Ph.D. project will bring information to understand how abiotic and abiotic conditions can shape genomic architecture in phytophagous insects, leading to (local) adaptation.

Jury

  • Jean PECCOUD, Université de Poitiers, CNRS, Rapporteur
  • Carole SMADJA, Université de Montpellier, CNRS, Rapporteuse
  • Jeanne ROPARS, Université Paris-Saclay, CNRS, Examinatrice
  • Yvan RHABÉ, Université de Lyon, INRAE, Examinateur
  • Amandine Cornille, Université Paris-Saclay, CNRS, Directrice de thèse