Molecular Paleoecology of Permafrost Mammals

永久冻土哺乳动物的分子古生态学

• 批准号: 9817937
• 负责人: Robert Wayne
• 金额: $ 39.46万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-06-01 至 2003-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9817937&HistoricalAwards=false
• 关键词: Molecular; Paleoecology; Permafrost; Mammals

The Arctic is well known as a unique scientific resource for biologybecause it contains exceptional records of past climatic fluctuations andthe concomitant interactions between biota and an extreme environment.Preliminary research has shown that the bones from animals from thepermafrost contain a further important record of global change - a geneticrecord, detailing faunal evolution through the Late Pleistocene.Preliminary studies reveal that ancient DNA techniques and the polymerasechain reaction (PCR) can be used to recover, amplify, and sequencemitochondrial DNA (mtDNA) of up to 600 base pairs (bp) in length from avariety of permafrost specimens from extensive deposits near Dawson, YukonTerritories and Fairbanks, Alaska. These permafrost deposits date from 20to 50 thousand years ago and contain thousands of bones from previousinhabitants of the area, making this resource a national treasure,comprising the largest collection of Pleistocene genetic information in theworld. In addition to testing long-standing systematic issues, DNA fromthese bones can be used to examine the consequences of past environmentalchanges, such as the opening of the Bering land bridge, and climate andanthropogenic effects on population genetics.Permafrost DNA will be used to examine several questions concerning theeffects of Late Pleistocene ecology on the genetics of modern populations,and how the effects of current environmental change and biologicalintroductions compare with that of the recent past. Mitochondrial controlregion and cytochrome b DNA sequences of approximately 200-300 bp will besequenced from about 20 specimens each of wolf (Canis lupus), moose (Alcesgigas) and elk (Cervus elaphus) to examine how genetic diversity haschanged since the Late Pleistocene. All three taxa have fossil records ofmore than several thousand years in North America, yet the geneticdiversity of modern North American populations is sufficiently limited thatrecent bottlenecks appear to have occurred. These results will becontrasted with those from analyses of the caribou (Rangifer tarandus) andthe brown bear (Ursus arctos), which also have a long record in NorthAmerica but have moderate amounts of genetic diversity in modernpopulations, perhaps due to large population sizes throughout the LatePleistocene.As well as examining changes in genetic diversity through time, thepermafrost DNA will be used to assess the relationship of Late Pleistocenepopulations to their modern counterparts. We will distinguish among fourpossible alternatives: 1) extant populations have DNA sequences that arephylogenetically distinct from those in the Old World and are directlyrelated to those from Late Pleistocene North American predecessors. Thisresult implies genetic continuity and continental isolation throughout theLate Pleistocene and that modern populations survived recent glacialconditions and megafaunal extinction events in relative isolation; 2) DNAsequences of modern populations do not share a common ancestry with thosein the permafrost implying that North American lineages went extinctsometime in the past 18,000 years and were replaced by those of an OldWorld ancestry existing in Beringia; 3) modern populations have a mixtureof DNA haplotypes that are related to those from the Late Pleistocene ofNorth America and the Old World implying recent admixture between Old andNew World populations; and 4) both modern and permafrost populations have amixture of DNA haplotypes of Old and New World ancestry implying a historyof continental mixing over the Late Pleistocene.Ancient DNA research has promised to allow evolutionary change tobe observed through real time but has been constrained by the number ofsamples and time frame that it has been possible to analyse. This projectwill fulfil that potential since it permits genetic change to be recordedin two large, well sampled natural populations (Fairbanks and Dawson) overa time frame of tens of thousands of years. It will also lead to a betterunderstanding of the factors involved in molecular preservation underpermafrost conditions, and suitable storage and handling regimes forspecimens uncovered by current mining operations. No organized collectingprogram currently exists for this valuable resource, and each year hundredsof specimens from this genetic museum are simply washed away downstream

北极作为一个独特的生物科学资源而闻名，因为它包含了过去气候波动以及生物群和极端环境之间伴随的相互作用的特殊记录。初步研究表明，来自永久冻土层的动物骨骼包含了全球变化的进一步重要记录--基因记录，详细介绍了晚更新世动物群的演变。初步研究表明，古代DNA技术和聚合酶链反应（PCR）可以用于恢复，扩增，以及来自道森、育空地区和阿拉斯加费尔班克斯附近大量沉积物的各种永久冻土标本中长达600个碱基对的线粒体DNA序列。这些永久冻土沉积物可以追溯到20至50万年前，包含该地区以前居民的数千块骨头，使这一资源成为国宝，包括世界上最大的更新世遗传信息收集。除了测试长期存在的系统性问题，这些骨骼的DNA还可以用来研究过去环境变化的后果，比如白令陆桥的开通，以及气候和人为因素对种群遗传学的影响。永久冻土DNA将被用来研究几个关于晚更新世生态学对现代种群遗传学影响的问题，以及当前环境变化和生物引入的影响与最近的过去相比如何。将对狼（Canis lupus）、驼鹿（Alcesgigas）和麋鹿（Cervus elaphus）各约20个标本的线粒体控制区和细胞色素B DNA序列进行测序，以研究晚更新世以来遗传多样性的变化。这三个分类群在北美都有几千年的化石记录，但现代北美种群的遗传多样性非常有限，以至于最近似乎出现了瓶颈。这些结果将与驯鹿的分析结果进行对比（Rangifer tarandus）和棕熊（Ursus arctos），它们在北美也有很长的记录，但在现代种群中具有中等数量的遗传多样性，这可能是由于整个晚更新世的大种群规模。冻土DNA将被用来评估晚更新世人口的关系，他们的现代同行。我们将区分四种可能的选择：1）现存种群的DNA序列在遗传上与旧大陆的DNA序列不同，并且与晚更新世北美祖先的DNA序列直接相关。这一结果意味着整个晚更新世的遗传连续性和大陆隔离，现代种群在最近的冰川条件和巨型动物灭绝事件中相对隔离地幸存下来：2）现代种群的DNA序列与永久冻土中的种群没有共同的祖先，这意味着北美血统在过去18,000年的某个时候消失了，并被白令吉亚的旧世界血统所取代;（3）现代人群的DNA单倍型与晚更新世北美和旧大陆人群的DNA单倍型有一定的相关性，这意味着新、旧大陆人群的混合;和4）现代人和永久冻土人的DNA单倍型混合了旧大陆和新大陆祖先的DNA单倍型，这意味着在晚更新世大陆混合的历史。古代DNA研究已经承诺允许观察进化变化通过真实的时间，但受到样本数量和时间范围的限制，它已经可以分析。这个项目实现了这一潜力，因为它允许基因变化被记录在两个大的，采样良好的自然种群（费尔班克斯和道森）超过数万年的时间框架。它还将导致更好地了解永久冻土条件下分子保存所涉及的因素，以及目前采矿作业所发现的标本的适当储存和处理制度。目前还没有一个有组织的收集计划来收集这种宝贵的资源，每年这个基因博物馆里的数百个标本都被冲走了。