Collaborative Research: LTREB Renewal: Long-Term Dynamics of Amphibian Populations Following Disease-Driven Declines

本项目将研究一种新型病原体入侵种群的过程，以一种真菌病原体在青蛙和蝾螈中引起壶菌病。人们日益认识到，新出现的传染病的爆发不仅是对人类的重大威胁，也是对野生动物的重大威胁，而且日益威胁到全球生物多样性。一种新型病原体最初侵入易感宿主种群可引起疾病暴发，导致高死亡率和种群规模下降。当这种情况发生时，宿主和病原体种群都可能发生自然选择，导致宿主对病原体感染的易感性和耐受性以及病原体损害宿主的能力（毒力）发生进化变化。这些变化可反过来决定宿主种群能否持续存在并从疾病中恢复。了解这些进化过程对于制定保护濒危物种的策略至关重要。壶菌病对全世界的两栖动物造成了灾难性的影响，并与近几十年来许多物种的灭绝和更多物种的濒危有关。在这种疾病侵入加州内华达山脉的数百个高海拔湖泊之后，研究人员将调查病原体和宿主（山黄腿蛙）的进化变化模式。这个项目将有助于了解诸如壶菌病等传染病作为自然种群进化变化的媒介的作用。它将为州和联邦机构提供关键信息，促进濒危物种的恢复，并将培训和教育本科生、研究生和公众。这项研究建立在对加利福尼亚内华达山脉复杂景观中山黄腿蛙（Rana sierrae和Rana muscosa）种群动态的长期研究数据的基础上，以及Batrachochytrium dendroatidis （Bd）的影响，因为它已经入侵并传播了数百个青蛙种群。在大多数情况下，Bd的入侵导致壶菌病的爆发，青蛙数量迅速下降和局部灭绝。在某些情况下，蛙种群的长期持续存在发生在一种地方病状态下，在这种状态下病原体的影响大大降低。该研究将扩展和利用25年来的宿主种群和疾病数据以及存档的sierra rrae/R遗传样本。这些资源将深入了解宿主和病原体种群在从病原体到达前到疾病暴发、到地方性动物疾病、到疾病前宿主种群丰度的潜在恢复的过渡过程中是如何变化的。该数据集将用于研究宿主抗性/耐受性和病原体毒力差异的遗传基础。现有青蛙和真菌样本的尖端基因组分析将补充利用野生宿主种群的Bd培养物和青蛙粘膜样本进行的Bd毒力和青蛙敏感性的实验室实验。对野生宿主种群的持续调查将确定新的疾病暴发，并描述从最初的暴发到持续的地方性兽疫状态的转变。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will examine the processes of invasion of a novel pathogen into a population for the case of a fungal pathogen that causes the disease chytridiomycosis in frogs and salamanders. Outbreaks of emerging infectious diseases are increasingly recognized as major threats, not just to human populations but also to wildlife, and they increasingly threaten global biodiversity. The initial invasion of a novel pathogen into a susceptible host population can cause a disease outbreak resulting in high levels of mortality and declines in population size. When this happens, natural selection can occur for both the host and pathogen populations resulting in evolutionary changes in the host's susceptibility and tolerance to infection by the pathogen and the pathogen's ability to damage the host (virulence). These changes can in turn determine whether the host population can persist and recover from the disease. Understanding these evolutionary processes is crucial in development of conservation strategies for threatened species. Chytridiomycosis has had catastrophic effects on amphibians worldwide, and has been linked to numerous species extinctions in recent decades and many more species at risk. The researchers will investigate the patterns of evolutionary change in both the pathogen and the host (mountain yellow-legged frogs), following the invasion of the disease into hundreds of high elevation lakes in the California Sierra Nevada. This project will contribute to the understanding of the role of infectious diseases, such as chytridiomycosis, as agents of evolutionary change in natural populations. It will provide critical information to state and federal agencies, facilitating endangered species recovery and will train and educate undergraduates, graduate students, and the general public.This research builds on data from a long-term study of the population dynamics of mountain yellow-legged frogs (Rana sierrae and Rana muscosa) in the complex landscape of the California Sierra Nevada, and the affects of Batrachochytrium dendrobatidis (Bd) as it has invaded and spread through hundreds of frog populations. In most cases, invasion of Bd results in outbreaks of the disease chytridiomycosis, rapid frog population declines, and local extinctions. In some cases, long-term persistence of frog populations occurs with Bd in an enzootic state in which the impact of the pathogen is greatly reduced. The research will extend and leverage 25 years of host population and disease data and archived genetic samples from R. sierrae/R. muscosa and Bd. These resources will provide insight into how populations of both host and pathogen change during the transition from pre-pathogen arrival, to disease outbreak, to enzootic disease, to potential recovery of the pre-disease host population abundances. This dataset will be used to investigate the genetic basis for differences in host resistance/tolerance and pathogen virulence. Cutting-edge genomic analysis of existing frog and fungal samples will complement laboratory experiments on Bd virulence and frog susceptibility using Bd cultures and frog mucosal samples from wild host populations. Continued surveys of wild host populations will identify new disease outbreaks and describe the transition from initial outbreak to persistent enzootic state.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.