Investigating the role of sexual conflict in parasitoid-host eco-evolutionary dynamics
Finding ways to grow enough food to sustain the ever-growing human population while minimising detrimental impacts on the natural environment is a pressing global challenge [1,2]. Current food production systems rely heavily on the use of agro-chemicals for pest control, the negative impacts of which are extreme for species, ecosystems and for climate change [3-7]. Integrated pest management (IPM) is one strategy that will be critical if we are to feed the human population without inflicting irreversible environmental damage. IPM prioritizes biodiversity-based pest control and considers the use of chemical pesticides only as a last resort .
Parasitoid wasps are a large group of insects, which are commonly used as a chemical-free means of controlling insect pests (biological control). Adults are free-living, females lay their eggs on or in other species and their offspring feed on this host, typically another insect, invariably killing it. In addition to their economic value, parasitoid wasps have long been used by blue skies researchers to understand fundamental questions about evolution, ecology and physiology [9,10]. This research has supported their use in crop protection and assisted biocontrol practitioners in selecting the most appropriate species to control a given pest [9,10].
Despite the abundance of studies on parasitoid behavioural ecology, these species have received little attention in studies of sexual selection and sexual conflict . Sexual conflict occurs when the optimum strategy or trait is different for males and females . For instance, the optimal mating rate is generally higher for males than females. This can result in reduced fitness for females if accepting or resisting superfluous male copulation attempts is costly [12, 13]. If these costs manifest as reduced offspring production, there can be consequences for recruitment and even population viability 
For parasitoid wasps in natural and agricultural settings, sexual conflict may have profound consequences for parasitism rates. Understanding the extent to which sexual conflict influences individual and population fitness in these insects provides new and valuable information on how aspects of these species’ mating systems can influence host-parasitoid dynamics and coevolution as well as the efficacy of pest control under different IPM scenarios.
This project aims to understand how sexual conflict in parasitoid wasps influences parasitism rates and the stability of host-parasitoid systems. The project will use a combination of individual-based modelling, lab-based fitness assays and field sampling using the sexual/asexual aphid parasitoid Lysiphlebus fabarum to address four main objectives:
1. Model the consequences of sexual conflict on parasitism rate and the fitness of parasitoid and host.
2. Assay the fitness of female L. fabarum that experience variation in sexual conflict through exposure to different numbers of males during oviposition in the lab.
3. Estimate variation in sexual conflict L. fabarum populations across the UK based on reproductive mode (sexual or asexual reproduction) and the sex ratio.
4. Test how the sex ratio and reproductive mode (sexual or asexual) influences the stability of host-parasitoid interactions at different spatial scales in L. fabarum .
The project will use the resevol R package (developed by supervisor Duthie ) as a foundation to model interactions between parasitoids and hosts depending on the sex ratio and its effects on fitness. This extension of the resevol package to include parasitoid-host dynamics and co-evolution will have applications beyond this project for the modelling of the likely success of parasitoid-based biocontrol in a range of agricultural scenarios. The empirical findings generated by this project will provide novel fundamental insights into how sexual conflict modifies host-parasitoid dynamics and the stability of their interactions in natural and agricultural settings.
The student should have a background in evolutionary ecology and experience in running lab-based fitness assays and conducting field work using insect model systems. Ideally the student will have some experience in insect rearing and data analysis and/or programming in R. The student will benefit from supervisor expertise in theory, individual-based modelling, lab-based experiments and field monitoring of parasitoid-host populations.