Fall armyworm migration across the Lesser Antilles and the potential for genetic exchanges between North and South American populations

Abstract

The fall armyworm, Spodoptera frugiperda (J. E. Smith)(Lepidoptera: Noctuidae), is an important agricultural pest of the Western Hemisphere noted for its broad host range, long distance flight capabilities, and a propensity to develop resistance to pesticides that includes a subset of those used in genetically modified corn varieties. These characteristics exacerbate the threat fall armyworm poses to agriculture, with the potential that a resistance trait arising in one geographical location could rapidly disseminate throughout the hemisphere. A region of particular concern is the Caribbean, where a line of islands that extends from Florida to Venezuela provides a potential migratory pathway between populations from North and South America that could allow for consistent and substantial genetic interactions. In this study, surveys of populations from Peru, Bolivia, Paraguay, and Trinidad & Tobago expand on previous work in South America that indicates a generally homogeneous population with respect to haplotype markers. This population differs from that found in most of the Lesser Antilles where a combination of genetic and meteorological observations is described that indicate fall armyworm migration from Puerto Rico to as far south as Barbados, but does not support significant incursion into Trinidad & Tobago and South America. Air transport projections demonstrate that the wind patterns in the Caribbean region are not conducive to consistent flight along the north-south orientation of the Lesser Antilles, supporting the conclusion that such migration is minor and sporadic, providing few opportunities for genetic exchanges. The implications of these findings on the dissemination of deleterious traits between the two Western Hemisphere continents are discussed.

Invasion origin, rapid population expansion, and the lack of genetic structure of cotton bollworm (Helicoverpa armigera) in the Americas

“…High genetic differentiation of H. armigera from South America and Puerto Rico show a limited gene flow between South and Central America. Low gene flow of Noctuidae pests between South and Central and North America was reported to Spodoptera frugiperda and H. zea (Leite, Corrêa, et al, ; Nagoshi et al, ). It is probably associated with contrary wind patterns between the South and North American continents that limit long‐distance dispersion of Noctuidae moths, providing few opportunities for gene flow.…”

Adaptation by copy number variation increases insecticide resistance in fall armyworms

“…This study is based on MS and PR, assuming that MS has a lower level of insecticide resistance than PR. The populations from Florida and the Caribbean have different mitochondrial haplotypes from the rest area of North and South American continents 46,47 , possibly due to the physical barrier effect of the Appalachian mountain range 48 and the limited genetic exchanges through the Lesser Antilles 47 . This grouping implies that the long-term seasonal migration of the fall armyworm is not sufficient for genetic exchanges between Puerto Rico and the Western area of the Appalachian mountain range to the observable extent.…”

Comparative molecular analyses of invasive fall armyworm in Togo reveal strong similarities to populations from the eastern United States and the Greater Antilles

“…The adjacent segment amplified by CO1 primers 891F and 1472R was used to confirm host strain identity and determine the region-specific haplotype metric [38] (Fig 2A). DNA sequence analysis of the SNPs at sites CO1 1164 and CO1 1287 identifies one rice-strain ( CO1 1164 = T, CO1 1287 = A) and four corn-strain haplotypes (h1-h4) defined by polymorphisms at two loci that together encompass the corn-strain group (Fig 2A).…”