The impact of diversity and multi-species interactions in disease ecology

预测疾病流行的威胁并减轻其影响是疾病生态学的基础。为此目的，可以从病原体和宿主容易被操纵的系统中学到很多东西。这是许多昆虫病原体的情况。在这里，我提出了三个研究目标，以确定病原体种群内变异的后果，病原体之间的相互作用以及宿主微生物组在两种昆虫系统中对疾病流行和传播的作用；西部帐篷毛虫的自然种群和白菜环虫的实验室种群。分子技术越来越允许鉴定病原体的遗传变异和在同一宿主中检测多种病原体。这使得探索病原体（如病毒）的遗传变异如何影响其毒力和传播成为可能。昆虫病毒的混合感染产生更高的宿主死亡率，但我们不知道这是否也意味着更大的人群传播。现场试验可用于测量疾病传播及其对宿主种群的影响。其次，我将研究不同病原体之间竞争的影响，以及多重感染是否会通过潜在的协同效应有利于微生物控制害虫，或者病原体之间的竞争是否会降低其有效性。最后，我将探讨昆虫肠道微生物群与宿主对病原体的抗性之间的相互作用。最近的研究表明，宿主微生物组可以影响致病生物的影响，但尚不清楚这些相互作用的方向。对野外采集的昆虫进行观察并对其肠道微生物群进行操作，将确定微生物是否可能相互作用以改变病原体的毒力和宿主的免疫力，以及由此产生的成本和收益。通过阐明可变病原体、宿主和微生物群落的影响，有可能在这两个模型系统中详细了解疾病动力学。这将导致建议如何更有效地利用病原体来加强和延长昆虫微生物控制的效力，并使人们更了解病原体在调节鳞翅目野外种群中的作用。

Predicting the threat of disease epidemics and mitigating their impacts is the underpinning of disease ecology. To this end much can be learned from systems in which pathogens and hosts can be easily manipulated. This is the case for many pathogens of insects. Here I propose three research objectives to determine the consequences of variation within pathogen populations, interactions among pathogens and the role of the host microbiome on disease prevalence and transmission in two insect systems; natural populations of western tent caterpillars and laboratory populations of cabbage loopers. Molecular techniques increasingly allow the identification of genetic variants of pathogens and the detection of multiple pathogen species in the same host. This allows exploration of how genetic variability of pathogens, such as viruses, influences their virulence and transmission. Mixed infections of insect viruses produce higher host mortality, but we do not know whether this also means greater transmission to the population. Field experiments can be used to measure disease transmission and impacts on host populations. Secondly I will investigate the influence of competition between different pathogens and whether multiple infections could benefit microbial control of insect plant pests by potentially having synergistic effects, or whether competition between the pathogens reduces their effectiveness. Finally I will explore the interactions between the insect gut microbiota and resistance of the host to pathogens. Recent work indicates that the host microbiome can influence the impact of pathogenic organisms but it is not clear what direction these interactions will go in. Observations of field collected insects and manipulations of their gut microbiota will determine if microorganisms might interact to modify the virulence of pathogens and the immunity of hosts and the costs and benefits of this. By elucidating the impacts of variable pathogens, hosts, and microbial communities, it is possible to develop a detailed understanding of disease dynamics in these two model systems. This will lead to recommendations of how pathogens can be used more effectively to enhance and prolong the efficacy of insect microbial control, and a greater knowledge of the role of pathogens in the regulation of field populations of Lepidoptera.