Sperm, sexual conflict, and sex allocation in parasitoid wasps

Supervisors: Dr David Shuker, Professor Leigh Simmons, Dr Rebecca Boulton

Project Description
This inter-disciplinary project, bringing together evolutionary biology and computer science, will use next-generation visualisation and computer modelling techniques to visualise how female insects store and use sperm. We will focus on group of biologically and economically important insects: parasitoid wasps. Parasitoid wasps attack and kill other insects. As such, they are crucial natural enemies of many insect pests and have been successfully used in biological control programmes all across the globe. The parasitic lifestyle shapes many aspects of their biology however, including their mating systems, patterns of sexual selection, and how females use sperm1. How female parasitoid wasps use sperm is very important in the Hymenoptera, since fertilised eggs develop into females, whilst unfertilised eggs develop into males. As such, how females control the fertilisation of their eggs will influence the sex ratio of their offspring. Sex ratio is itself a very important fitness trait for parasitoids: typically, across parasitoids, females are selected to vary their offspring sex ratios facultatively with respect to environmental factors such as host quality or expected degree of sibling competition for mates2. Sex ratio is also an important trait though for their success as natural enemies or biological control agents, since it is only females that – by laying eggs on or in their insect hosts – attack pest species. Moreover, commercial rearing of parasitoids for biological control would greatly benefit from being able to maximise female offspring production.

In the parasitoid wasp Nasonia vitripennis, females vary their offspring sex ratios in line with the predictions of Local Mate Competition (LMC) theory. However, we have recently shown that their ability to use sperm effectively and produce optimal sex ratios can be hampered by interactions with males, particularly when females mate multiply and when multiple ejaculates interact inside the female reproductive tract3. It is well known that in many species of parasitoid females are able to be incredibly thrifty when using sperm, in some cases releasing only a single sperm to fertilise individual eggs. Such control – whilst impressive – may well involve processes of sperm preparation and storage that the presence of multiple ejaculates disrupt. In this project, the successful applicant will use a range of techniques to unravel the dynamics of sperm use in Nasonia vitripennis and other parasitoids, both to understand the fundamental biology of sperm use in parasitoids, but also to help us develop strategies to manipulate sex ratios for biological control programmes.

The project will provide a number of key training opportunities: (1) experimental design and behavioural techniques in the laboratory; (2) quantitative skills, from data management through to statistical analysis; (3) bioimaging techniques, including micro CT scanning and sperm imaging; (4) developing new computer modelling techniques for bioimaging; (5) management of high-throughput digital information; (6) communication skills, to academic, industrial and non-technical audiences.

We recommend informal enquiries to Dr David Shuker.


1. Boulton, R.A., Collins, L.A. & Shuker, D.M. (2015) Beyond sex allocation: the role of mating systems in sexual selection in parasitoid wasps. Biological Reviews, 90: 599-627.

2. West, S.A. (2009) Sex Allocation. Princeton University Press, Princeton.

3. Boulton, R.A. & Shuker, D.M. (2015) A sex allocation cost to polyandry in a parasitoid wasp. Biology Letters, 11: 20150205.