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

传染病可以通过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物种灭绝的诱因，无论是单独或与辅助因素(如气候变化)结合在一起，但从现代实例中可以明显看出，疾病可以对自然人口的健康状况产生非同寻常的影响。在这一提议中，有人认为：(1)疾病导致的灭绝发生在最近的过去(更新世晚期)；(2)这些损失是由于遗传上幼稚的动物种群遭遇了由迁徙的人类、它们的共生体或同源人类从其他地方带来的传染病(它们的共生体或共生体)，这些新宿主随后迅速出现，导致灾难性的死亡；以及(2)病原体的经验证据可以从晚更新世的物质中恢复，利用分子(“古老的”DNA)和免疫学方法(从而允许对该假说进行现实测试)。这项工作的目标灭绝事件是大约11,000年前发生在北美和北亚的一系列重大损失。主要的目标分类群是猛犸象，一种毛茸茸的猛犸象，之所以选择它，是因为它代表着丰富的高质量化石(包括软组织)。为了系统和系统发育的目的，许多实验室也在用分子方法对该分类群进行大量研究，为结果的质量控制提供了一个很好的数据库。在可能的情况下，还将利用晚更新世的其他分类群，以及骨骼以外的遗骸(特别是粪便)。其目的是在团队成员在泰米尔半岛、西伯利亚和其他地区收集的保存完好的化石中寻找病原体(特别是病毒)的证据。通过相关实验验证的假设在一系列步骤中逻辑上联系在一起。实验可分为以下几类：第一组实验与这样一种假设有关：在已灭绝物种的组织和粪便中，可以用免疫化学方法检测到针对病毒感染而产生的外源病毒衣壳蛋白或宿主抗体。实验的目的是使用放射免疫分析(RIA)、酶联免疫吸附分析(ELISA)和免疫-PCR来检测DNA和RNA病毒。第二组实验与以下假设相关联：使用为单拷贝核DNA分析而开发的古老DNA技术可以检测化石样本中的外源DNA病毒。实验的目的是获得RIA鉴定的DNA病毒的序列信息。第三组实验与这样的假设有关：由于遗传一致性，猛犸象种群的适合度可能降低(因此对疾病的易感性增加)。实验旨在分析地理和时间上离散的猛犸象样本的群体遗传学，以寻找遗传瓶颈的证据。在化石材料中检测和表征病毒成分的任何成功都将是开创性的，从而有可能在基因水平上经验性地跟踪病毒在数千年的趋势期内的进化变化。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、座谈会和网络产品传播成果。

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.