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Genetic architecture of sexual and asexual populations of the aphid Rhopalosiphum padi based on allozyme and microsatellite markers.

Abstract

Cyclical parthenogens, including aphids, are attractive models for comparing the genetic outcomes of sexual and asexual reproduction, which determine their respective evolutionary advantages. In this study, we examined how reproductive mode shapes genetic structure of sexual (cyclically parthenogenetic) and asexual (obligately parthenogenetic) populations of the aphid Rhopalosiphum padi by comparing microsatellite and allozyme data sets. Allozymes showed little polymorphism, confirming earlier studies with these markers. In contrast, microsatellite loci were highly polymorphic and showed patterns very discordant from allozyme loci. In particular, microsatellites revealed strong heterozygote excess in asexual populations, whereas allozymes showed heterozygote deficits. Various hypotheses are explored that could account for the conflicting results of these two types of genetic markers. A strong differentiation between reproductive modes was found with both types of markers. Microsatellites indicated that sexual populations have high allelic polymorphism and heterozygote deficits (possibly because of population subdivision, inbreeding or selection). Little geographical differentiation was found among sexual populations confirming the large dispersal ability of this aphid. In contrast, asexual populations showed less allelic polymorphism but high heterozygosity at most loci. Two alternative hypotheses are proposed to explain this heterozygosity excess: allele sequence divergence during long-term asexuality or hybrid origin of asexual lineages. Clonal diversity of asexual lineages of R. padi was substantial suggesting that they could have frozen genetic diversity from the pool of sexual lineages. Several widespread asexual genotypes were found to persist through time, as already seen in other aphid species, a feature seemingly consistent with the general-purpose genotype hypothesis.

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  • Publisher Full Text
  • Authors

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    Source

    Molecular ecology 11:4 2002 Apr pg 711-23

    MeSH

    Alleles
    Animals
    Aphids
    Enzymes
    Female
    Gene Frequency
    Genetic Variation
    Genetics, Population
    Male
    Microsatellite Repeats
    Parthenogenesis
    Reproduction
    Reproduction, Asexual

    Pub Type(s)

    Journal Article
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    11972759

    Citation

    TY - JOUR T1 - Genetic architecture of sexual and asexual populations of the aphid Rhopalosiphum padi based on allozyme and microsatellite markers. AU - Delmotte,F, AU - Leterme,N, AU - Gauthier,J-P, AU - Rispe,C, AU - Simon,J-C, PY - 2002/4/26/pubmed PY - 2002/7/18/medline PY - 2002/4/26/entrez SP - 711 EP - 23 JF - Molecular ecology JO - Mol. Ecol. VL - 11 IS - 4 N2 - Cyclical parthenogens, including aphids, are attractive models for comparing the genetic outcomes of sexual and asexual reproduction, which determine their respective evolutionary advantages. In this study, we examined how reproductive mode shapes genetic structure of sexual (cyclically parthenogenetic) and asexual (obligately parthenogenetic) populations of the aphid Rhopalosiphum padi by comparing microsatellite and allozyme data sets. Allozymes showed little polymorphism, confirming earlier studies with these markers. In contrast, microsatellite loci were highly polymorphic and showed patterns very discordant from allozyme loci. In particular, microsatellites revealed strong heterozygote excess in asexual populations, whereas allozymes showed heterozygote deficits. Various hypotheses are explored that could account for the conflicting results of these two types of genetic markers. A strong differentiation between reproductive modes was found with both types of markers. Microsatellites indicated that sexual populations have high allelic polymorphism and heterozygote deficits (possibly because of population subdivision, inbreeding or selection). Little geographical differentiation was found among sexual populations confirming the large dispersal ability of this aphid. In contrast, asexual populations showed less allelic polymorphism but high heterozygosity at most loci. Two alternative hypotheses are proposed to explain this heterozygosity excess: allele sequence divergence during long-term asexuality or hybrid origin of asexual lineages. Clonal diversity of asexual lineages of R. padi was substantial suggesting that they could have frozen genetic diversity from the pool of sexual lineages. Several widespread asexual genotypes were found to persist through time, as already seen in other aphid species, a feature seemingly consistent with the general-purpose genotype hypothesis. SN - 0962-1083 UR - https://www.unboundmedicine.com/medline/citation/11972759/Genetic_architecture_of_sexual_and_asexual_populations_of_the_aphid_Rhopalosiphum_padi_based_on_allozyme_and_microsatellite_markers_ L2 - http://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0962-1083&date=2002&volume=11&issue=4&spage=711 ER -