DISSERTATION RESEARCH: Evolutionary Consequences of Pathogen Strain Competition in an Emerging Fungal Disease

本计画将探讨不同致病性真菌菌株间的生态竞争与演化动态的相互影响。新发现的疾病是对生物多样性和人类健康的重大威胁。许多新出现的疾病都是由真菌病原体引起的。然而，很少有研究涉及致病真菌的进化生态学。一种臭名昭著的新出现的真菌疾病是杀死两栖动物的壶菌，它导致了世界范围内两栖动物的减少和生物多样性的丧失。尽管自1999年发现以来进行了深入的研究，但这种疾病的起源和进化轨迹仍然是一个谜。该项目将调查巴西南部大西洋森林中壶菌多样性高的区域，以了解不同真菌菌株之间的竞争如何决定这些病原体的成功和进化。了解新出现的疾病如何演变，对于控制未来的疾病暴发至关重要。该项目包括对本科生和研究生的培训，沿着K-12外展计划和博物馆展览，突出介绍疾病对生态系统健康的影响。先前的研究表明，巴西大西洋森林中不同的两栖动物杀手壶菌菌株正在争夺宿主。根据理论，相互竞争的疾病菌株应该进化得具有更快的生长速度和更强的毒性，直到一个最成功的菌株消灭了所有其他菌株。该项目将调查这些壶菌疾病菌株最初是如何接触的，以及这种接触的生态和进化结果。研究人员将使用从该地区收集的病原体分离株的全基因组序列重建巴西大西洋森林疾病菌株的分歧历史。然后，他们将在两栖动物宿主模型上进行跨品系竞争实验。实验前后将对实验病原体菌株的基因组进行测序，以将竞争后毒力的基因型变化与表型变化联系起来。这些数据将使研究人员能够确定病原体种群之间接触的时间，并确定是否由于菌株之间的直接竞争而加速了毒力的演变。

This project will investigate the interplay of ecological competition and evolutionary dynamics among different strains of pathogenic fungi. Newly discovered, emerging diseases are a significant threat to biological diversity and human health. Many of these emerging diseases are caused by fungal pathogens. Yet few studies have addressed the evolutionary ecology of disease-causing fungi. A notorious emerging fungal disease is the amphibian-killing chytrid fungus, which is contributing to worldwide amphibian declines and biodiversity loss. Despite intensive research since its discovery in 1999, the origins and evolutionary trajectory of this disease remain a mystery. This project will investigate a region of high chytrid diversity in the Atlantic Forest of southern Brazil to understand how competition among different fungal strains determines the success and evolution of these pathogens. Understanding how emerging diseases evolve will be critical to controlling future disease outbreaks. The project includes the training of undergraduate and graduate students, along with K-12 outreach programs and museum displays that highlight effects of introduced diseases on ecosystem health.Prior research suggests that divergent amphibian-killing chytrid strains in Brazil's Atlantic Forest are competing for hosts. According to theory, competing disease strains should evolve to have faster rates of growth and increased virulence until a single most successful strain has eliminated all others. This project will investigate how these chytrid disease strains initially came into contact, and the ecological and evolutionary outcomes of this contact. The researchers will reconstruct the divergence history of Brazilian Atlantic Forest disease strains using whole genome sequences of pathogen isolates collected from the region. They will then conduct a cross-strain competition experiment on a model amphibian host. The genomes of experimental pathogen strains will be sequenced before and after the experiment to link genotypic changes to phenotypic change in post-competition virulence. These data will allow the researchers to establish the timing of contact between pathogen populations, and to determine if accelerated virulence evolves due to direct competition among strains.