ARS | Publication request: Spatial genetic variation among Spodoptera frugiperda (Lepidoptera: Noctuidae) sampled from the United States, Puerto Rico, Panama, and Argentina

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 10, 2011
Publication Date: March 7, 2012
Citation: Belay, D.K., Clark, P.L., Skoda, S.R., Isenhour, D.J., Molina-Ochoa, J., Gianni, C., Foster, J.E. 2012. Spatial genetic variation among Spodoptera frugiperda (Lepidoptera: Noctuidae) sampled from the United States, Puerto Rico, Panama, and Argentina. Annals of the Entomological Society of America. 105(2): 359-367.

Interpretive Summary: The fall armyworm (FAW), a migratory and polyphagous pest, is the most economically important pest of corn in the western hemisphere. Understanding the genetic diversity and gene flow of FAW can help pest managers develop appropriate management strategies. We used a technique of molecular genetics, amplified fragment length polymorphism (AFLP), to investigate the genetic diversity of FAW. Representative samples of about 30 individuals were collected from 31 locations in the Western Hemisphere i.e. United States, Argentina, Panama, and Puerto Rico. Analysis of data generated by AFLP showed most of the genetic variability (71 %) to have been from individuals sampled from the same location; 28% of variability was from locations nearest each other, i.e. from the same country; less than 1% of genetic variability was from groups of distant locations. These results indicate substantial gene flow between FAW from different locations. Separate analysis of those samples from locations near each other, i.e. from the same country, indicated that in samples from Argentina there was somewhat less gene flow; perhaps local barriers in Argentina are restricting the movement, and therefore the gene flow, of FAW. These results can be used by pest management personnel to develop management strategies and, if resistance to insecticides were to develop in FAW, to monitor the relevant changes in genetic diversity of FAW.

Technical Abstract: The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a migratory and polyphagous pest of both cultivated and uncultivated plant species in the Western Hemisphere. Understanding the genetic diversity and gene flow of this economically important pest can help to develop appropriate management strategies. We have investigated the genetic diversity of FAW by collecting 31 representative samples from the Western Hemisphere i.e. United States, Argentina, Panama, and Puerto Rico and then using amplified fragment length polymorphism (AFLP). Analysis of molecular variance (AMOVA) revealed that the majority (71.2%) of the total variation is within populations; the remaining 28% of the variation was among populations within groups indicating the presence of significant gene flow among FAW populations in the Western Hemisphere. Similarly dendrograms of results from cluster analysis showed the lack of genetic structuring i.e. the samples were randomly clustered in close proximity. Moreover, the isolation by distance analysis indicated that there is no significant correlation between genetic dissimilarity and geographic distance for the entire population, suggesting the presence of substantial gene flow. However, the dependency of genetic distance on geographic distance was significant for FAW samples collected from Argentina probably due to the presence of local barriers that led to change in allele frequency and subsequent genetic isolation. The results of the study are important to develop management strategies and resistance monitoring.