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Adaptive introgression across semipermeable species boundaries between local and invasive Helicoverpa mega-pest moths

Valencia Montoya, Wendy Andrea (2019) Adaptive introgression across semipermeable species boundaries between local and invasive Helicoverpa mega-pest moths. Research Project 2, Ecology and Evolution.


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Cross-breeding between invasive and native species, has raised global concern given the dramatic increase in species range shifts and pest outbreaks due to climate change, development of suitable agroecosystems, and anthropogenic dispersal. Nevertheless, secondary contact between diverged lineages of local and invasive species provides a natural laboratory to understand the factors that determine introgression and the maintenance or loss of species barriers. Here, we characterize the early evolutionary outcomes following secondary contact between invasive Helicoverpa armigera and H. zea mega-pest moths in Brazil. We carried out whole-genome resequencing of Helicoverpa moths from Brazil in two temporal samples: soon after H. armigera invasion in 2013, and more recent populations from 2017. There is evidence for a burst of hybridization and widespread introgression from local H. zea into invasive H. armigera coinciding with H. armigera expansion in 2013. However, in H. armigera admixture proportions were reduced between 2013 and 2017, suggesting a decline in hybridization rates. Recent populations also showed shorter introgressed tracks suggesting selection against admixture. In contrast to the genome-wide pattern, there was striking evidence for introgression of a single region including an insecticide-resistance allele from the invasive H. armigera into local H. zea, which increased in frequency over time but was localized within the genome. In summary, despite extensive gene-flow after secondary contact, the species boundaries are maintained except for the single introgressed region containing the insecticide-resistant locus. We document the worst case scenario for an invasive species, in which there are now two pest species instead of one, and the native species has acquired resistance to pyrethroid insecticides.

Item Type: Thesis (Research Project 2)
Supervisor nameSupervisor E mail
Supervisor (outside RUG):
Supervisor outside RUG nameSupervisor outside RUG E mail
Degree programme: Ecology and Evolution
Thesis type: Research Project 2
Language: English
Date Deposited: 18 Jul 2019
Last Modified: 18 Jul 2019 13:32

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