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Spodoptera frugiperda (Lepidoptera: Noctuidae) host-plant variants: two host strains or two distinct species?

Dumas P, Legeai F, Lemaitre C, Scaon E, Orsucci M, Labadie K, Gimenez S, Clamens AL, Henri H, Vavre F, Aury JM, Fournier P, Kergoat GJ, d'Alençon E - Genetica (2015)

Bottom Line: We found a significant reduction of mating success in F1 in one direction of the cross and a high level of microsatellite markers showing transmission ratio distortion in the F2 progeny.Our results support the existence of post-zygotic reproductive isolation between the two laboratory strains and are in accordance with the marked level of genetic differentiation that was recovered between individuals of the two strains collected from the field.Altogether these results provide additional evidence in favor of a sibling species status for the two strains.

View Article: PubMed Central - PubMed

Affiliation: UM - UMR 1333 DGIMI, Université Montpellier, Place Eugène Bataillon, 34095, Montpellier, France, pascalinedumas@gmail.com.

ABSTRACT
The moth Spodoptera frugiperda is a well-known pest of crops throughout the Americas, which consists of two strains adapted to different host-plants: the first feeds preferentially on corn, cotton and sorghum whereas the second is more associated with rice and several pasture grasses. Though morphologically indistinguishable, they exhibit differences in their mating behavior, pheromone compositions, and show development variability according to the host-plant. Though the latter suggest that both strains are different species, this issue is still highly controversial because hybrids naturally occur in the wild, not to mention the discrepancies among published results concerning mating success between the two strains. In order to clarify the status of the two host-plant strains of S. frugiperda, we analyze features that possibly reflect the level of post-zygotic isolation: (1) first generation (F1) hybrid lethality and sterility; (2) patterns of meiotic segregation of hybrids in reciprocal second generation (F2), as compared to the meiosis of the two parental strains. We found a significant reduction of mating success in F1 in one direction of the cross and a high level of microsatellite markers showing transmission ratio distortion in the F2 progeny. Our results support the existence of post-zygotic reproductive isolation between the two laboratory strains and are in accordance with the marked level of genetic differentiation that was recovered between individuals of the two strains collected from the field. Altogether these results provide additional evidence in favor of a sibling species status for the two strains.

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Related in: MedlinePlus

Crossing protocol used to follow microsatellite markers segregation patterns in F2 populations within- and inter-strains. Circles and squares symbolize females and males respectively
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Fig1: Crossing protocol used to follow microsatellite markers segregation patterns in F2 populations within- and inter-strains. Circles and squares symbolize females and males respectively

Mentions: Between 27 and 30 isolated couples (using different males and females, to avoid pseudo-replications in the dataset) were constituted for each type of crosses: both C female × R male (one corn female with one rice male; C/R) and R female × C male (one rice female with one corn male; R/C) inter-strain crosses directions and both R female × R male (one rice female with one rice male; R/R) and C female × C male (one corn female with one corn male; C/C) within-strain crosses (Fig. 1). In order to avoid paternity ambiguity, the sex of pupae was anatomically determined before emergence, and pupae of both sexes were reared separately. Virgin females were collected at emergence, and allowed to mate with a single male for five days. The number of couples with hatched larvae was counted and progeny of three couples for each kind of cross were reared in laboratory up to the pupal stage in order to determine sex of pupae. To analyze the ratio of cross giving a viable progeny between all type of cross (i.e. C/C, R/R, C/R, R/C), we used a generalized linear model (GLM) with binomial distribution because the data were binaries (i.e. 0 no progeny, one progeny). The model contained two following factors: the strain female (C or R) and the strain male (C or R), and, we also included the interaction between the two factors (strain female × strain male). Model selection was performed as follow: significance of the different terms was tested starting from the higher-order terms using likelihood-ratio-test (LRT). Non-significant terms (p > 0.05) were removed (Crawley 2012). Factor levels of qualitative variables that were not significantly different were grouped (LRT; Crawley, 2012). All computations were performed using the R software version 3.0.3.Fig. 1


Spodoptera frugiperda (Lepidoptera: Noctuidae) host-plant variants: two host strains or two distinct species?

Dumas P, Legeai F, Lemaitre C, Scaon E, Orsucci M, Labadie K, Gimenez S, Clamens AL, Henri H, Vavre F, Aury JM, Fournier P, Kergoat GJ, d'Alençon E - Genetica (2015)

Crossing protocol used to follow microsatellite markers segregation patterns in F2 populations within- and inter-strains. Circles and squares symbolize females and males respectively
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4419160&req=5

Fig1: Crossing protocol used to follow microsatellite markers segregation patterns in F2 populations within- and inter-strains. Circles and squares symbolize females and males respectively
Mentions: Between 27 and 30 isolated couples (using different males and females, to avoid pseudo-replications in the dataset) were constituted for each type of crosses: both C female × R male (one corn female with one rice male; C/R) and R female × C male (one rice female with one corn male; R/C) inter-strain crosses directions and both R female × R male (one rice female with one rice male; R/R) and C female × C male (one corn female with one corn male; C/C) within-strain crosses (Fig. 1). In order to avoid paternity ambiguity, the sex of pupae was anatomically determined before emergence, and pupae of both sexes were reared separately. Virgin females were collected at emergence, and allowed to mate with a single male for five days. The number of couples with hatched larvae was counted and progeny of three couples for each kind of cross were reared in laboratory up to the pupal stage in order to determine sex of pupae. To analyze the ratio of cross giving a viable progeny between all type of cross (i.e. C/C, R/R, C/R, R/C), we used a generalized linear model (GLM) with binomial distribution because the data were binaries (i.e. 0 no progeny, one progeny). The model contained two following factors: the strain female (C or R) and the strain male (C or R), and, we also included the interaction between the two factors (strain female × strain male). Model selection was performed as follow: significance of the different terms was tested starting from the higher-order terms using likelihood-ratio-test (LRT). Non-significant terms (p > 0.05) were removed (Crawley 2012). Factor levels of qualitative variables that were not significantly different were grouped (LRT; Crawley, 2012). All computations were performed using the R software version 3.0.3.Fig. 1

Bottom Line: We found a significant reduction of mating success in F1 in one direction of the cross and a high level of microsatellite markers showing transmission ratio distortion in the F2 progeny.Our results support the existence of post-zygotic reproductive isolation between the two laboratory strains and are in accordance with the marked level of genetic differentiation that was recovered between individuals of the two strains collected from the field.Altogether these results provide additional evidence in favor of a sibling species status for the two strains.

View Article: PubMed Central - PubMed

Affiliation: UM - UMR 1333 DGIMI, Université Montpellier, Place Eugène Bataillon, 34095, Montpellier, France, pascalinedumas@gmail.com.

ABSTRACT
The moth Spodoptera frugiperda is a well-known pest of crops throughout the Americas, which consists of two strains adapted to different host-plants: the first feeds preferentially on corn, cotton and sorghum whereas the second is more associated with rice and several pasture grasses. Though morphologically indistinguishable, they exhibit differences in their mating behavior, pheromone compositions, and show development variability according to the host-plant. Though the latter suggest that both strains are different species, this issue is still highly controversial because hybrids naturally occur in the wild, not to mention the discrepancies among published results concerning mating success between the two strains. In order to clarify the status of the two host-plant strains of S. frugiperda, we analyze features that possibly reflect the level of post-zygotic isolation: (1) first generation (F1) hybrid lethality and sterility; (2) patterns of meiotic segregation of hybrids in reciprocal second generation (F2), as compared to the meiosis of the two parental strains. We found a significant reduction of mating success in F1 in one direction of the cross and a high level of microsatellite markers showing transmission ratio distortion in the F2 progeny. Our results support the existence of post-zygotic reproductive isolation between the two laboratory strains and are in accordance with the marked level of genetic differentiation that was recovered between individuals of the two strains collected from the field. Altogether these results provide additional evidence in favor of a sibling species status for the two strains.

Show MeSH
Related in: MedlinePlus