Host resistance and within-host competition between leaf-cutting ant parasites with opposing transmission strategies

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Parasites have significant effects on host biology. Most research has focussed on infections by single, virulent parasites that cause obvious disease. However, infections frequently involve more than one parasite, many of which may appear relatively avirulent and thus hard to detect. Although their effects may be more subtle, these cryptic parasites can nevertheless have important effects on host fitness. Furthermore, they may influence the infection success of other, perhaps more virulent, parasites either by reducing the host's immune response or by directly inhibiting the infection of the other parasite. This project will investigate the interactions between hosts and parasites in leaf-cutting ants infected by a virulent fungal pathogen and/or an avirulent bacterial parasite. It will examine if host genotypes and phenotypes differ in resistance to the avirulent parasite and if the same hosts are also resistant to the virulent pathogen. It will also establish if infection by the apparently avirulent parasite reduces host immunity. Finally it will determine the infection success of the virulent pathogen in hosts that are either infected by, or free from, the avirulent parasite. Together these results will shed important light on the role of more cryptic parasites in the biology both of hosts, and other more obvious pathogens.