Testing trade-offs between signalling and immune function using a novel approach to quantify eukaryotic parasite burdens

Project Details

Key Questions

What is the role of parasitism and immunity in maintaining the honesty of quality signals? 


For signals to be useful, the information they provide must be reliable. Animals signal their quality when competing for resources and when courting prospective mates but despite much theoretical and empirical work the mechanisms that maintain signal honesty in animal populations remain contentious. This project will explore the idea that signalling imposes immunity costs, such that only individuals of high quality can afford to signal at a high intensity. To test this, we will make use of a novel and powerful method for passively sampling the microeukaryotic parasite communities of wild vertebrates. By manipulating levels of competition for resources, we can then track how levels of signalling vary with parasite burdens to determine the extent to which immunity costs maintain signal honesty. 

Aims of the Project

The aim of this project is to characterise the condition-dependence of intra- and intersexual signals of quality by determining how investment in aggression and courtship vary with microeukaryotic parasite burdens. 

Project Description

For signals to be useful, the information they provide must be reliable, yet by cheating and providing unreliable information individuals often stand to gain at the expense of others. A central goal of animal behaviour research has therefore been to understand how signal honesty is maintained within animal populations. While much of the debate around honest signalling remains contentious, there is a general consensus that for signals to be honest they must impose costs that make it unprofitable for low-quality individuals to cheat and signal that they are of high quality. One form these costs could take is reduced immune function, which could arise either through allocation of resources to signal expression at the expense of immunity, or via negative impacts of components of the signal on immune function. Indeed, it has even been suggested that the intensity of signals may provide receivers with information about the immune status and likely parasite burden of signallers. 

To date, there is mixed evidence for an association between the intensity of signals produced by males during courtship and infection status. Notably, although signalling by females is also common (for example, in competition over resources), almost nothing is known about the relationship between signalling and immunity in females. A significant limitation of previous research is the focus on only one or a small number of parasite species. In reality, investment in signalling is unlikely to trade-off with defence against a single parasite; instead, it is important to determine the relationship between signal expression and features (abundance, richness and diversity) of entire parasite communities. This project will make use of a novel and powerful method for passively sampling the microeukaryotic parasite communities from the faeces of wild vertebrates based on metabarcoding. Crucially, this approach allows us to look at costs to immunity from the perspective of the entire assemblage of parasites that infect a host. Furthermore, this method is non-invasive and allows us to sample individuals repeatedly to determine the extent of covariation between signal expression and parasite burdens. In this way, it will be possible to establish the role of parasite-related immunity costs in ensuring signal honesty in both males and females. 

This project is jointly supervised by Dr Jonathan Green within the Department of Zoology at the University of Oxford, who has expertise in the study of animal behaviour, including signalling, and Prof. Beth Okamura and Dr Andrew Briscoe at the Natural History Museum, London, who have expertise in the study of microeukaryotic parasite communities using metabarcoding. There is considerable freedom to develop specific research questions in line with the candidate’s interests and there are a number of animal systems (for example, fish or birds) that could be used to explore links between signalling, immunity and parasites

Methods to be used

The project will involve a combination of behavioural experiments in the lab and/or field and analysis of environmental DNA from faecal microeukaryotic communities using a novel metabarcoding method. 

Specialised skills required

The student will receive training in all the methods needed to carry out the research. 

Please contact Jonathan Green on jonathan.green@zoo.ox.ac.uk if you are interested in this project