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

寄生虫对宿主生物学有重要影响。大多数研究都集中在由单一的、致命的寄生虫引起的感染上，这些寄生虫会导致明显的疾病。然而，感染通常涉及不止一种寄生虫，其中许多寄生虫可能看起来相对无毒，因此难以发现。尽管它们的影响可能更微妙，但这些隐寄生物仍然可以对宿主的适应性产生重要影响。此外，它们可能会通过降低宿主的免疫反应或直接抑制其他寄生虫的感染，从而影响其他可能毒性更强的寄生虫的感染成功。本项目将研究被一种强毒真菌病原体和/或一种无毒细菌寄生虫感染的切叶蚁的宿主和寄生虫之间的相互作用。它将检查宿主基因型和表型在对无毒寄生虫的抗性方面是否不同，以及相同的宿主是否也对有毒病原体具有抗性。它还将确定感染这种看似无毒的寄生虫是否会降低宿主的免疫力。最后，它将决定在被无毒寄生虫感染或不受其感染的宿主中，毒性病原体的感染成功与否。综上所述，这些结果将对更多的隐蔽性寄生虫在宿主和其他更明显的病原体生物学中的作用提供重要的启示。

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.