LTREB : Collaborative Research: Long-term dynamics of amphibian populations following disease-driven declines

新出现的传染病的暴发日益被认为是对野生动物种群的主要威胁。一种新的病原体最初入侵易感宿主人群可引起疾病暴发，从而导致高水平的死亡率和种群数量的下降。当这种情况发生时，在疾病暴发期间，宿主和病原体种群都可能发生自然选择。这可能导致宿主对病原体感染的敏感性和耐受性发生进化变化。它还可以改变病原体损害宿主的能力(毒力)。这些变化反过来又决定了宿主种群能否持续并从疾病中恢复过来。了解这些进化过程对于制定保护受威胁物种的战略至关重要。这个项目将研究一种真菌病原体的情况，这种病原体导致青蛙和火蜥蜴的棘霉病。这种疾病对世界各地的两栖动物造成了灾难性的影响，近几十年来有大量物种灭绝的记录，还有更多的物种处于危险之中。在疾病入侵加利福尼亚州内华达山脉数百个高海拔湖泊后，研究人员将调查病原体和宿主(山地黄腿青蛙)的进化变化模式。该项目将有助于理解作为自然种群进化变化动因的传染病的作用，如合孢子菌病。它将向州和联邦机构提供关键信息。它还将培训和教育无数的本科生和研究生以及普通公众。这项研究基于对加州内华达山脉复杂地貌中山地黄腿蛙(Rana sierrae和Rana MusCosa)种群动态以及蝙蝠(Batrachochytrium Dendrobatidis，Bd)的影响的长期研究数据，因为它已经入侵并传播到数百个青蛙种群。在大多数情况下，Bd的入侵会导致该病的暴发，青蛙数量迅速下降，并导致局部灭绝。然而，在某些情况下，青蛙种群的长期存在是由于Bd处于地方病状态，在这种状态下，病原体的影响大大减少。这项研究将利用分子方法的最新进展，以及来自R.sierrae/R.Muscosa-Bd系统的大量样本集和存档，来研究宿主和病原体在从病原体到达前到疾病暴发到地方病，再到可能恢复病前宿主种群丰度的转变过程中的变化。这个数据集将被用来研究寄主抗性/耐性和病原菌毒力差异的遗传基础。对现有拭子样本的尖端基因组分析将与对野外种群的持续调查相结合，以识别新的疾病暴发，并描述从暴发到地方性疾病状态的转变，从野外种群收集Bd培养物和青蛙粘膜样本，以及Bd毒力和青蛙的实验室实验。

Outbreaks of emerging infectious diseases are increasingly recognized as major threats to wildlife populations. 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 on both the host and pathogen populations during the disease outbreak. This can result in evolutionary changes in the host's susceptibility and tolerance to infection by the pathogen. It can also change 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. This project will examine these processes for the case of a fungal pathogen that causes the disease Chytridiomycosis in frogs and salamanders. This disease has had catastrophic effects on amphibians worldwide, with numerous species extinctions documented 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. It will also train and educate numerous, undergraduates and graduate students as well as 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 impacts 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 however 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 make use of recent advances in molecular approaches, and the extensive dataset and archive of samples from the R. sierrae/R. muscosa - Bd system, to investigate 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 swab samples will be combined with continued surveys of field populations to identify new disease outbreaks and describe the transition from outbreak to enzootic state, collection of Bd cultures and frog mucosal samples from field populations, and laboratory experiments on Bd virulence and frog