title: Targeted re-sequencing confirms the importance of chemosensory genes in aphid host race differentiation.
abstract: Host-associated races of phytophagous insects provide a model for understanding how adaptation to a new environment can lead to reproductive isolation and speciation, ultimately enabling us to connect barriers to gene flow to adaptive causes of divergence. The pea aphid (Acyrthosiphon pisum) comprises host races specializing on legume species and provides a unique system for examining the early stages of diversification along a gradient of genetic and associated adaptive divergence. As host choice produces assortative mating, understanding the underlying mechanisms of choice will contribute directly to understanding of speciation. As host choice in the pea aphid is likely mediated by smell and taste, we use capture sequencing and SNP genotyping to test for the role of chemosensory genes in the divergence between eight host plant species across the continuum of differentiation and sampled at multiple locations across western Europe. We show high differentiation of chemosensory loci relative to control loci in a broad set of pea aphid races and localities, using a model-free approach based on principal component analysis. Olfactory and gustatory receptors form the majority of highly differentiated genes and include loci that were already identified as outliers in a previous study focusing on the three most closely related host races. Consistent indications that chemosensory genes may be good candidates for local adaptation and barriers to gene flow in the pea aphid open the way to further investigations aiming to understand their impact on gene flow and to determine their precise functions in response to host plant metabolites.
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Alfred Denny Building, Sheffield, S10 2TN, UK.
authors.forename: Isobel
authors.initials: I
authors.lastname: Eyres
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Alfred Denny Building, Sheffield, S10 2TN, UK.
authors.forename: Ludovic
authors.identifier: http://orcid.org/0000-0003-0960-0312
authors.initials: L
authors.lastname: Duvaux
authors.affiliation: Edinburgh Genomics, Ashworth Laboratories, University of Edinburgh, EH9 3JT, Edinburgh, UK.
authors.forename: Karim
authors.initials: K
authors.lastname: Gharbi
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Alfred Denny Building, Sheffield, S10 2TN, UK.
authors.forename: Rachel
authors.initials: R
authors.lastname: Tucker
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Alfred Denny Building, Sheffield, S10 2TN, UK.
authors.forename: David
authors.initials: D
authors.lastname: Hopkins
authors.affiliation: Institut de Génétique, Environnement et Protection des Plantes, UMR 1349 IGEPP, Domaine de la Motte, INRA, 35653, Le Rheu Cedex, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Simon
authors.affiliation: Department of Biology, University of York, York YO10 5DD, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Ferrari
authors.affiliation: Institut des Sciences de l'Evolution (UMR 5554 CNRS-IRD-CIRAD-Université de Montpellier), Université de Montpellier, cc065, Place Bataillon, Campus Triolet, 34095, Montpellier Cedex 05, France.
authors.forename: Carole M
authors.initials: CM
authors.lastname: Smadja
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Alfred Denny Building, Sheffield, S10 2TN, UK.
authors.forename: Roger K
authors.initials: RK
authors.lastname: Butlin
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics; D000818:Animals; D001042:Aphids / Q000235:genetics*; D005060:Europe; D007887:Fabaceae; D051456:Gene Flow; D017344:Genes, Insect; D005838:Genotype; D020641:Polymorphism, Single Nucleotide; D018035:Receptors, Odorant / Q000235:genetics*; D060047:Reproductive Isolation
chemical_list: D018035:Receptors, Odorant
keywords: 
  Acyrthosiphon pisum
  ; adaptation; chemosensory genes; genome scan; speciation; targeted resequencing