Abstract
Migrant populations of Helicoverpa zea (Boddie) captured during 2002, 2005, 2016, and 2018 from Landisville and Rock Springs in Pennsylvania, USA were genotyped using 85 single nucleotide polymorphism (SNP) markers. Samples (n = 702) genotyped were divided into 16 putative populations based on collection time and site. Fixation indices (F-statistics), analysis of molecular variance, and discriminant analysis of principal components were used to examine within and among population genetic variation. The observed and expected heterozygosity in putative populations ranged from 0.317–0.418 and 0.320–0.359, respectively. Broad range of FST (0.0–0.2742) and FIS (0.0–0.2330) values indicated different genotype frequencies between and within the populations, respectively. High genetic diversity within and low genetic differentiation between populations was found in 2002 and 2005. Interestingly, high genetic differentiation between populations from two collection sites observed in 2018 populations was not evident in within-site comparisons of putative populations collected on different dates during the season. The shift of H. zea population genetic makeup in 2018 may be influenced by multiple biotic and abiotic factors including tropical storms. Continued assessment of these peripheral populations of H. zea will be needed to assess the impacts of genetic changes on pest control and resistance management tactics.
Highlights
Insect species living in temperate climatic zones with broad geographic distributions and long-range migration capacity disperse seasonally throughout habitable geographic regions when favorable conditions arise
Filtering resulted in 894,576 tags, of which 601,201 (67.2%) and 58,752 (6.6%) were aligned to unique and multiple positions of the H. zea genome, respectively, and 234,623 reads (26.2%) could not be aligned
After Tassel pipeline analysis, a total of 15,669, 7477 and 2664 VCF, unfiltered hapmap, and filtered hapmap single nucleotide polymorphism (SNP), respectively were detected within GBS reads from 95 H. zea
Summary
Insect species living in temperate climatic zones with broad geographic distributions and long-range migration capacity disperse seasonally throughout habitable geographic regions when favorable conditions arise. Admixtures of genetically diverse source populations from different regions to seasonal peripheral populations provide opportunities for robust exchange of genetic material that may be carried back to the source populations during reverse migration at the end of each warm season The extent of this genetic admixture is dependent on multiple factors including the effective population sizes, temporal reproductive overlap, dispersal rate, growth rate, and food source preference [2,3,4]. This fundamental process influences genetic diversity and high gene flow rates between immigrants within peripheral populations from geographically separated source populations, leading to panmixis [3,5]. Genetic analyses of such species may reveal high genetic diversity and low genetic differentiation among source populations
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