The genus Helicoverpa consists of two of the world’s most damaging crop pests – H. armigera, common throughout Afro-Eurasia, and H. zea, native to the Americas. The sepcies are difficult to manage because of their broad host plant range, dispersal ability, capacity for facultative diapause and resistance to a broad range of pesticides. H. armigera, which is particularly damaging to cotton, is more genetically diverse, more polyphagous and resistant to a larget set of pesticides. H. zea prefers maize, and has evolved resistance to a range of Bt toxins in its native range. In 2013, H. armigera was detected in South America where it hybridized with native H. zea despite substantial phenotypic and genetic divergence between the two species in the time since they diverged 1.5-2MYA.

We showed that alleles conferring pyrethroid resistance were introduced to South American H. zea through adaptive introgression, and more recently that these alleles have spread into the North American H. zea population. Through a joint BBSRC-FAPESP research project and other collaborations, we are investigating the long-term outcome of hybridization and gene exchange between these species. To this end we have assembled a time-series dataset of whole-genome resequencing data from more than 1000 individuals spanning the course of the invasion from 2013 to the present. In addition, we are using GWAS and linkage mapping approaches to understand the fitness effects of inter-species gene exchange over time.  

We have previously worked on the diamondback moth (Plutella xylostella) – another global crop pest that has evolved field resistance to a wide variety of insecticides and Bt toxins.  Using genetic linkage mapping and genomic approaches we have identified the genes for resistance to Bt toxin and spinosad. These discoveries have facilitated the management of resistance and future studies aimed at ameliorating resistance.

  Publications:

North, Henry L., et al. "Rapid adaptation and interspecific introgression in the North American crop pest Helicoverpa zea." Molecular Biology and Evolution (2024): msae129

Jin, M., North, H. L., Peng, Y., Liu, H., Pan, R., Zhou, Y., et al. "Adaptive evolution to the natural and anthropogenic environment in a global invasive crop pest, the cotton bollworm." The Innovation (2023).

North, Henry L., Angela McGaughran, and Chris D. Jiggins. "Insights into invasive species from whole‐genome resequencing." Molecular Ecology 30.23 (2021): 6289-6308.

Valencia-Montoya, Wendy A., et al. "Adaptive introgression across semipermeable species boundaries between local Helicoverpa zea and invasive Helicoverpa armigera moths." Molecular biology and evolution 37.9 (2020): 2568-2583.

Baxter, S. W. et al. Linkage mapping and comparative genomics using next-generation RAD sequencing of a non-model organism. PLoS ONE 6, e19315 (2011).

Baxter, S. W. et al. Parallel evolution of Bacillus thuringiensis toxin tesistance in Lepidoptera. Genetics 189, 675–679 (2011)

Baxter, S. W. et al. Mis-Spliced Transcripts of Nicotinic Acetylcholine Receptor α6 Are Associated with Field Evolved Spinosad Resistance in Plutella xylostella (L.). PLoS Genet 6, e1000802 (2010)