Megafaunal Mammal Genetics and Extinction Dynamics in the Late Pleistocene: Testing the Hyperdisease Hypothesis

晚更新世巨型动物遗传学和灭绝动力学：检验超疾病假说

• 批准号: 0117400
• 负责人: Ross MacPhee
• 金额: --
• 依托单位: American Museum Natural History
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-15 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0117400&HistoricalAwards=false
• 关键词: Megafaunal; Mammal; Genetics; Extinction; Dynamics

Infectious diseases can influence evolutionary mechanisms in a variety of ways, including extinction of host populations. While disease is rarely considered as a forcing agent in extinction, whether alone or in combination with co factors (e.g., climate change), it is nevertheless obvious from modern examples that disease can have extraordinary effects on the fitness of natural populations. In this proposal it is contended that: (1) extinctions due to disease have occurred in the recent past (late Pleistocene); (2) these losses were prompted by genetically naive populations of animals encountering infectious diseases brought from elsewhere by migrating humans, their commensals, or synanthropics), which quickly emerged thereafter in these new hosts, causing catastrophic mortality; and (2) empirical evidence of pathogens is recoverable from late Pleistocene material, utilizing molecular ("ancient" DNA) and immunological approaches (thereby permitting realistic tests of the hypothesis).The target extinction event for this work is the major series of losses that occurred in North America and northern Asia ca. 11,000 years ago. The principal target taxon is Mammuthus primigenius, the woolly mammoth, chosen because it is represented by abundant, high-quality fossils (including soft tissues). This taxon is also being heavily investigated by molecular methods for systematic and phylogenetic purposes in a number of labs, providing a good database for quality control of results. Other late Pleistocene taxa will also be utilized where feasible, as will remains other than bones (especially feces). The intent is to search for evidence of pathogenic entities (in particular, viruses) in well-preserved fossils collected by team members in the Taimyr Peninsula, Siberia, as well as other locales.Hypotheses to be tested by relevant experiments are logically linked in a series of steps. Experiments may be grouped as follows:Group 1 experiments are linked to the hypothesis that exogenous virus capsid proteins or host antibodies raised against virus infection can be detected immunochemically in tissues and feces of extinct species. Purpose of experiments is to use radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), and immuno-PCR to detect DNA and RNA viruses.Group 2 experiments are linked to the hypothesis that exogenous DNA viruses in fossil samples can be detected using ancient DNA techniques developed for single-copy nuclear DNA analysis. Purpose of experiments is to obtain sequence information on DNA viruses identified by RIA.Group 3 experiments are linked to the hypothesis that mammoth populations may have suffered from reduced fitness (and therefore increased susceptibility to disease) as the result of genetic uniformity. Experiments are designed to analyze population genetics of geographically and temporally discrete mammoth samples, to look for evidence of genetic bottlenecking.Any success in detecting and characterizing viral elements in fossil material will be groundbreaking, leading to the possibility of being able to empirically track evolutionary change in viruses at the gene level over periods of tends of thousands of years. Further, if the expected correlations between taxa, pathogens, and extinction times can be shown to be meaningful, this will have substantial impact on evolutionary biology, conservation biology, and virology. Dissemination of results through publications, symposia, and Web products is planned.

传染病可以以各种方式影响进化机制，包括宿主种群的灭绝。虽然疾病很少被认为是灭绝的强迫因素，无论是单独的还是与其他因素（如气候变化）结合在一起，但从现代的例子中可以明显看出，疾病对自然种群的适合度可以产生非凡的影响。在这个提议中，有人认为：(1)由于疾病导致的灭绝发生在最近的过去（晚更新世）；(2)这些损失是由于遗传上幼稚的动物种群遇到了由迁徙的人类（他们的共生体或共生体）从其他地方带来的传染病，这些传染病随后在这些新的宿主中迅速出现，造成灾难性的死亡；(2)利用分子（“古代”DNA）和免疫学方法，可以从晚更新世材料中获得病原体的经验证据（从而允许对假设进行现实测试）。这项研究的目标灭绝事件是大约11000年前发生在北美和北亚的一系列主要灭绝事件。主要的目标分类群是猛犸象（Mammuthus primigenius），即长毛猛犸象，之所以选择它，是因为它拥有丰富的、高质量的化石（包括软组织）。许多实验室正在对该分类群进行系统和系统发育的分子方法研究，为结果的质量控制提供了良好的数据库。其他晚更新世分类群也将在可行的情况下加以利用，骨头以外的遗骸（特别是粪便）也将加以利用。其目的是在西伯利亚泰米尔半岛以及其他地区的团队成员收集的保存完好的化石中寻找致病实体（特别是病毒）的证据。要通过相关实验验证的假设在一系列步骤中是有逻辑联系的。实验可分为以下几类：第一组实验与假设有关，即可以在灭绝物种的组织和粪便中通过免疫化学方法检测到外源病毒衣壳蛋白或针对病毒感染而产生的宿主抗体。实验目的是利用放射免疫法（RIA）、酶联免疫吸附法（ELISA）和免疫pcr检测DNA和RNA病毒。第2组实验与化石样本中的外源DNA病毒可以使用为单拷贝核DNA分析开发的古代DNA技术进行检测的假设有关。本实验的目的是获取RIA鉴定的DNA病毒的序列信息。第3组实验与猛犸象种群可能由于遗传一致性而遭受适应性降低（从而增加对疾病的易感性）的假设有关。实验旨在分析地理上和时间上离散的猛犸象样本的种群遗传学，以寻找遗传瓶颈的证据。在化石材料中检测和表征病毒元素的任何成功都将是开创性的，从而有可能在数千年的时间里在基因水平上经验地追踪病毒的进化变化。此外，如果分类群、病原体和灭绝时间之间的预期相关性能够被证明是有意义的，这将对进化生物学、保护生物学和病毒学产生重大影响。计划通过出版物、专题讨论会和网络产品传播结果。