PhD student Henry North has been awarded a Cambridge Society for the Application of Research (CSAR) PhD Student Award, which recognises outstanding research with real world application.

Henry is an evolutionary biologist who studies the genomics of invasive crop pests. He is based at the Department of Zoology in the lab of Professor Chris Jiggins (who is well-known for his work on the speciation of tropical butterflies).

Henry says, "Growing up in Queensland, Australia, I was surrounded by a wealth of biodiversity. At the same time, I could see the devastating effects of invasive species like lantana bushes and cane toads in my own back yard. After completing undergraduate studies in Australia, an Erasmus Mundus scholarship allowed me to carry out a series of evolutionary genomics research internships at the University of Montpellier, Harvard University, and the Department of Zoology here in Cambridge."

His research applies the tools of evolutionary theory to understand invasive species. His PhD research centers on a small, unprepossessing moth in the genus Helicoverpa, also known as the cotton bollworm or corn earworm.

"They are very hungry caterpillars and the most economically significant crop pests in the world," says Henry. "The larvae eat everything - maize, soy, wheat, rice, sorghum, tomato - most of the calories that humans consume."

The moths are widespread, found throughout Africa, Europe, Asia and Australia, spreading rapidly in flights large enough to detect using ground-based radar. A decade ago the Afro-Eurasian species H. armigera  was introduced to Brazil, where they hybridized with the native species H. zea. In doing so, they conferred pesticide-resistant genes to the native moths. In a recent paper published in Molecular Biology and Evolution, Henry and colleagues have shown that these hybrids have now spread to North America as well.

The class of pesticides to which the moths have developed resistance are synthetic pyrethroids, which Henry describes as "inexpensive, and dumped in huge numbers in both North and South America. The scale here is important. For instance, in Brazil, soy plantations cover an area the size of Germany. So you have massive monocultures that these resistant pests can just rip through. The damage they cause in Brazil is huge - in the order of billions of US dollars per year."

Henry studies how this resistance is acquired by identifying the specific genes of interest. "For my PhD, I was lucky to work with a range of collaborators who collected individuals every year from ten sites in Brazil, from 2013 until last year, so we have a nice time series. Then we look at the whole genome of each of the sample insects. This is where applying evolutionary biology becomes useful, because by looking at patterns of genetic diversity between individuals you can identify which alleles have recently been introduced and which are the targets of natural selection."

Ongoing work in the lab involves treating the moths with pesticides to see which individuals survive. "We can then see whether the same alleles under selection in the field are statistically associated with pesticide resistance in the lab." Those alleles are strongly selected for in response to pesticide exposure, and so lead to very rapid evolution, "at timescales relevant to year-to-year pest management strategies."

The application of this genomic data has the potential for great impact because the resistant insects can be identified to agricultural agencies and farmers to help model, monitor and manage the spread of invasive species that threaten ecosystems and agro-economies. Using - and overusing - the wrong pesticides encourages more resistance in both target and non-target pests. 

The pests have also recently become resistant to Bt (Bacillus thuringienses, a biopesticide used to treat caterpillars). Bt toxins are preferable to the synthetic pyrethroids because they are ingested by the pests and specifically target Lepidotera - butterflies and moths. Henry is now planning to research which strains of Bt might keep specific populations under control. "The idea is to try to figure out a way to forecast where the pests are going to spread. You can't predict evolution, but you can model population growth to offer guidance on the efficacy of new Bt strains and the regions particularly at risk of infestation." These targeted Bt strains can then be applied directly or introduced into genetically modified plants to help keep the pests at bay.

Henry will submit his thesis this month, and is heading to Brazil in September to meet agriculturalists and scientists, "people on the ground dealing with this pest to figure out if any of our thinking is wrong or if there is anything we have not thought about in our planned future work." It's important, he says, to work as part of a team and engage with local experts.

Following that, he will take up the Tucker-Price Research Fellowship in Zoology at Girton College to continue his Helicoverpa research, as well as on invasive species in the UK.

We wish Henry all the best with his future research and congratulate him on the prize.

Papers

Henry L North, Zhen Fu, Richard Metz, Matt A Stull, Charles D Johnson, Xanthe Shirley, Kate Crumley, Dominic Reisig, David L Kerns, Todd Gilligan, Tom Walsh, Chris D Jiggins, Gregory A Sword, Rapid Adaptation and Interspecific Introgression in the North American Crop Pest. Molecular Biology and Evolution, Volume 41, Issue 7, July 2024, msae129, https://doi.org/10.1093/molbev/msae129

Angela McGaughran, Manpreet K Dhami, Elahe Parvizi, Amy L Vaughan, Dianne M Gleeson, Kathryn A Hodgins, Lee A Rollins, Carolyn K Tepolt, Kathryn G Turner, Kamolphat Atsawawaranunt, Paul Battlay, Carlos Congrains, Angelica Crottini, Tristan P W Dennis, Claudia Lange, Xiaoyue P Liu, Paige Matheson, Henry L North, Iva Popovic, Marc Rius, Anna W Santure, Katarina C Stuart, Hui Zhen Tan, Cui Wang, Jonathan Wilson, Genomic Tools in Biological Invasions: Current State and Future Frontiers, Genome Biology and Evolution, Volume 16, Issue 1, January 2024, evad230,  https://doi.org/10.1093/gbe/evad230