Hybridization and introgression between Helicoverpa zea and H. armigera: an adaptational bridge

The invasion of organisms into new
ecosystems is an increasingly common phenomenon due to the movement of
commodities in global trade. One of the most complex scenarios post-invasion is
when the invasive species resembles a native pest; even more so when they can
hybridize and produce fertile progeny. The global pest Helicoverpa armigera had been
detected in Brazil in 2013 and generated a wave of speculations about the
possibility of hybridization with the native sister taxa Helicoverpa zea. In the present study, we used genome-wide SNPs
genotyped in field-collected individuals to investigate hybridization between H. armigera and H. zea in different Brazilian agricultural landscapes. The results indicated that the frequency
of hybridization varied from 15 to 30% depending on methods used. Mix ancestry
between H. zea and H. armigera in hybrids (introgression)
was around 10% in all tested methods. Hybridization also varied considerably depending
on the geographic locations where the sample was collected, forming a ‘mosaic’
hybrid zone where introgression may be facilitated by environmental and
landscape variables. Both landscape composition and bioclimatic variables point
to the presence of maize and soybean as the main factors explaining the high percentage
of introgression in agriculture landscapes. In addition, the impact of multiple
H. armigera incursions is reflected in
the structured and inbred pattern genetic diversity. Our data show that the landscape
composition and bioclimatic variables influence in the introgression rate
between H. armigera and H. zea in agricultural areas. The continuous monitoring of the hybridization process
in the agricultural fields is necessary since agricultural expansion, climatic
fluctuations, a changing composition of crop species and varieties, and dynamic
planting seasons are some factors in South America that could promote a sudden alteration
in the introgression rate between Helicoverpa spp. Introgression between
invasive and native pests also can dramatically impact evolution on host ranges
and resistance management.