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Genetic signature of amphimixis allows for the detection and fine scale localization of sexual reproduction events in a mainly parthenogenetic nematode.

Abstract

Asexuality is an important mode of reproduction in eukaryotic taxa and has a theoretical advantage over sexual reproduction because of the increased ability to propagate genes. Despite this advantage, hidden signs of cryptic sex have been discovered in the genomes of asexual organisms. This has provided an interesting way to address the evolutionary impact of sex in plant and animal populations. However, the identification of rare sexual reproduction events in mainly asexual species has remained a challenging task. We examined the reproductive history in populations of the plant parasitic nematode Xiphinema index by genotyping individuals collected from six grapevine fields using seven microsatellite markers. A high level of linkage disequilibrium and heterozygous excess suggested a clonality rate of 95-100%. However, we also detected rare sexual reproduction events within these highly clonal populations. By combining highly polymorphic markers with an appropriate hierarchical sampling, and using both Bayesian and multivariate analysis with phylogenetic reconstructions, we were able to identify a small number of sexually produced individuals at the overlapping zones between different genetic clusters. This suggested that sexual reproduction was favoured when and where two nematode patches came into contact. Among fields, a high degree of genetic differentiation indicated a low level of gene flow between populations. Rare genotypes that were shared by several populations suggested passive dispersal by human activities, possibly through the introduction of infected plants from nurseries. We conclude that our method can be used to detect and locate sexual events in various predominantly asexual species.

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  • Authors

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    Source

    Molecular ecology 19:5 2010 Mar pg 856-73

    MeSH

    Alleles
    Animals
    Bayes Theorem
    DNA, Helminth
    Gene Flow
    Genetic Variation
    Genetics, Population
    Genotype
    Linkage Disequilibrium
    Microsatellite Repeats
    Multivariate Analysis
    Nematoda
    Phylogeny
    Reproduction
    Sequence Analysis, DNA

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    20102516