Understanding the ecological and genomic drivers of biocontrol system stability

Biocontrol acts as an effective, pesticide free and non-GMO method of controlling invasive species. However, decline in efficacy of a successful biocontrol system can have devastating consequences for native ecosystems, agriculture, and the economy. Argentine stem weevil (ASW), a significant rye grass pest that was controlled by the effective biocontrol agent Microctonous hyperodae, used to have overwinter parasitism rates of 70%; however, 7 years after its original release, there was a significant decline in parasitism rates. Researchers hypothesised that this decline was due to the evolution of resistance by the ASW to M. hyperodae, likely caused by the strong selective pressure imposed by high initial parasitism rates. The clover root weevil (CRW) is currently controlled by M. aethiopoides and, with multiple similarities in seasonality, biotype and ecology to the ASW system, M. aethiopoides could similarly fail as a biocontrol agent for CRW in the future. Investigating the potential for such failure is critical, since CRW represents an exceptional threat to the New Zealand dairy industry. My PhD project will use population genomics tools to understand how specific genetic differences within/between populations may be associated with biocontrol failure and success. In addition, the microbiomes of insect species have been shown to influence their behavior, reproduction, and interactions with other species, thus examination of microbial communities, including endosymbionts, will help determine differences among parasitoid wasp populations. I will therefore perform metagenomic studies to understand microbial diversity and abundance across different populations of M. aethiopoides to examine the potential role of the microbiome in biocontrol success. Finally, temperature plays a crucial role in influencing the behavior of both wasps and their host weevils, which in turn may impact parasitism effectiveness. Thus, I will test the impact of different temperatures on host-parasitoid interactions at the transcriptomic level to elucidate the wasp's biology and its mechanisms of response to changing environments, including via changes in gene expression and metabolic pathways.