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  • Publication
    Accès libre
    Population genetic structure of two primary parasitoids of Spodoptera frugiperda (Lepidoptera), Chelonus insularis and Campoletis sonorensis (Hymenoptera): to what extent is the host plant important?
    (2010)
    Jourdie, Violaine
    ;
    Alvarez, Nadir
    ;
    Molina-Ochoa, Jaime
    ;
    Williams, Trevor
    ;
    Bergvinson, David
    ;
    ; ;
    Franck, Pierre
    Plant chemistry can strongly influence interactions between herbivores and their natural enemies, either by providing volatile compounds that serve as foraging cues for parasitoids or predators, or by affecting the quality of herbivores as hosts or prey. Through these effects plants may influence parasitoid population genetic structure. We tested for a possible specialization on specific crop plants in Chelonus insularis and Campoletis sonorensis, two primary parasitoids of the fall armyworm, Spodoptera frugiperda. Throughout Mexico, S. frugiperda larvae were collected from their main host plants, maize and sorghum and parasitoids that emerged from the larvae were used for subsequent comparison by molecular analysis. Genetic variation at eight and 11 microsatellites were respectively assayed for C. insularis and C. sonorensis to examine isolation by distance, host plant and regional effects. Kinship analyses were also performed to assess female migration among host-plants. The analyses showed considerable within population variation and revealed a significant regional effect. No effect of host plant on population structure of either of the two parasitoid species was found. Isolation by distance was observed at the individual level, but not at the population level. Kinship analyses revealed significantly more genetically related—or kin—individuals on the same plant species than on different plant species, suggesting that locally, mothers preferentially stay on the same plant species. Although the standard population genetics parameters showed no effect of plant species on population structure, the kinship analyses revealed that mothers exhibit plant species fidelity, which may speed up divergence if adaptation were to occur.
  • Publication
    Accès libre
    Identification of seven species of hymenopteran parasitoids of Spodoptera frugiperda, using polymerase chain reaction amplification and restriction enzyme digestion
    (2008)
    Jourdie, Violaine
    ;
    Alvarez, Nadir
    ;
    1 The fall armyworm Spodoptera frugiperda is a voracious pest of numerous crops of economic importance throughout the New World. In its native Mexico, larvae can be attacked by several species of parasitic wasps, which are candidate biological control agents against this and other lepidopteran pests.
    2 We attempted to survey the parasitoid fauna on S. frugiperda in maize and sorghum fields throughout Mexico. However, our efforts have been hampered by the incomplete development of parasitoid larvae emerging from collected Spodoptera caterpillars.
    3 This problem was solved by developing a method to identify seven species of parasitic wasps using polymerase chain reaction amplification and restriction enzyme digestion. This enables the precise determination of the species of those parasitoid larvae that are usually not morphologically identifiable.
  • Publication
    Accès libre
    Isolation and characterization of polymorphic microsatellite loci in two primary parasitoids of the noctuid Spodoptera frugiperda: Chelonus insularis and Campoletis sonorensis (Hymenoptera)
    (2008)
    Jourdie, Violaine
    ;
    Alvarez, Nadir
    ;
    ;
    Franck, Pierre
    Fifteen and 13 microsatellite loci were isolated, respectively, from Campoletis sonorensis Cameron and from Chelonus insularis Cresson. These two parasitic Hymenoptera are primary parasitoids of Lepidoptera in North, Central and South America, including the important agricultural pest Spodoptera frugiperda. Allelic diversity and heterozygosity were quantified in samples from Mexico. Each locus was polymorphic, with the number of alleles ranging from two to 16 in C. sonorensis and from four to 18 in C. insularis. Heterozygosity ranged from 0.088 to 0.403 in C. sonorensis and from 0.106 to 0.458 in C. insularis.