Biology Reference
In-Depth Information
the common ancestor of the two strains was retained during their divergence,
or interstrain hybridization. The goal to identify diagnostic, and unique, AFLP
markers failed and McMichael and Prowell (1999) concluded that future studies,
in which AFLP data are combined with mt markers and allozymes, might resolve
the hybridization question. Later, Pashley et  al. (2004) compiled mtDNA data,
an esterase locus and eight AFLP loci in moths collected in Louisiana, Florida,
Puerto Rico, Guadeloupe and French Guiana and concluded that 16% of indi-
viduals were potentially hybrids with a minority being F1 progeny. The hybrids
were found primarily in corn, a habitat used by both strains. Pashley et  al.
(2004) stated, “these data support introgressive hybridization between recently
evolved species that are not completely reproductively isolated.” The molecu-
lar data, in combination with other data, have shown the two populations are
different and explain a long-standing concern of practical pest-management
importance. Whether these populations are called species, incipient species, or
host races is a judgment call that is based on whether the scientist is a “splitter”
or a “lumper.”
Another issue of relevance to pest-management specialists is where the
fall armyworm overwinters and how it colonizes crops in the northern United
States; efforts to understand their migrations previously were based on trapping
fall armyworm adults ( Nagoshi and Meagher 2008 ). Nagoshi et  fall (2009) used
COI mt genes to determine that most “corn” populations in the United States
overwinter in southern Texas and Florida and adults from central Pennsylvania
originated from Texas.
Studies of the fall armyworm in South America indicated two biotypes are
present that have different host-plant preferences and other biological and
ecological differences ( Nagoshi et  al. 2007 ). PCR-RFLP analysis of populations
from Brazil indicated the mt haplotypes found in corn in Brazil were geneti-
cally distinct from corn populations in Florida and suggested future studies
could resolve whether corn populations in South and Central America were of
the Brazil or Florida haplotype, which could resolve questions about the long-
range movements of these populations. Clark et al. (2007) conducted AFLP anal-
yses of 23 populations from Mexico, the United States, Puerto Rico, Brazil, and
Argentina and concluded that the majority of genetic variability is within popu-
lations and not between populations, suggesting there is minor gene flow and
that the corn moths in the Western Hemisphere “are an interbreeding popula-
tion.” They stated, “ S. frugiperda is highly genetically variable.”
Arias et  al. (2011) evaluated 174 microsatellite markers using the method
developed by Techen et  al. (2010) and screened 15 moths from eight families
Search WWH ::




Custom Search