Abstract
In 2013, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) was officially declared as present in Brazil and, after two years, the species was detected in the Caribbean and North America. Information on genetic features and accurate distribution of pests is the basis for agricultural protection policies. Furthermore, such knowledge is imperative to develop control strategies, understand the geographical range, and genetic patterns of this species in the Americas. Here, we carried out the widest sampling of H. armigera in the South American continent and Puerto Rico, after we estimated the diversity, demographic parameters, and genetic structure. The Internal Transcribed Spacer 1 (ITS1) nuclear marker was used to investigate the presence of putative hybrids between H. armigera and H. zea, and they were observed at a frequency of 1.5%. An ABC analysis, based in COI gene fragment, suggested Europe as the origin of South America specimens of H. armigeraand following a movement northward through the Caribbean. Three mtDNA genes and three nDNA markers revealed high genetic diversity distributed without the defined population structure of H. armigera in South America. Most of the genetic variation is within populations with a multidirectional expansion of H. armigera among morphoclimatic regions. High genetic diversity, rapid population expansion, and hybridization have implications for pest management since they suggest that adaptive alleles are spread through wide areas in South America that favor rapid local adaptation of H. armigera to new and disturbed environments (e.g., in agricultural areas).
Highlights
The agribusiness sector accounts for more than 20% of the Brazilian gross domestic product (GDP) (IBGE, 2016)
We used seven different nu‐ clear and mitochondrial molecular markers in order to (a) elucidate the invasion routes of H. armigera populations in South America, (b) assess the demographic parameters and population structure of H. armigera populations from Brazil, its bordering countries, and Puerto Rico, (c) assess the gene flow among H. armigera population collected in different Brazilian regions, and (d) investigate the presence of putative hybrids between H. armigera and H. zea in Brazil
For simulations of the models, the values of the parameters were sampled randomly within the intervals whose maximum lim‐ its were calculated as follows: Wang, Fan, Owada, Wang, and Nylin (2014) detected the rate of 0.0115 substitutions/site/million years for c oxidase subunit I (COI) in Noctuidae, we considered 0.75 million years as the maximum coalescence time of the sequences, five generations per year (Ge, Chen, Parajulee, & Yardim, 2005; Naseri, Fathipour, Moharramipour, & Hosseininaveh, 2011) and the‐ ta‐W = 4.123, which was obtained in DnaSp v5 (Librado & Rozas, 2009) from the 626bp COI dataset long with 92 sequences
Summary
The agribusiness sector accounts for more than 20% of the Brazilian gross domestic product (GDP) (IBGE, 2016). We used seven different nu‐ clear and mitochondrial molecular markers in order to (a) elucidate the invasion routes of H. armigera populations in South America, (b) assess the demographic parameters and population structure of H. armigera populations from Brazil, its bordering countries, and Puerto Rico, (c) assess the gene flow among H. armigera population collected in different Brazilian regions, and (d) investigate the presence of putative hybrids between H. armigera and H. zea in Brazil Such information is important in helping to define immedi‐ ate control strategies and long‐term solutions for Helicoverpa man‐ agement in South America and providing substantial information to support prevention and preparedness for the imminent arrival of the pest in the main North America agricultural regions
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