Collaborative Research: Analysis of a Forty Thousand Year Record of Genetic and Environmental Change in the Arctic

这是加州大学洛杉矶分校和圣克鲁斯分校、阿拉斯加大学费尔班克斯分校和史密森学会的主要研究人员的合作提案。该奖项将由生物学和北极自然科学计划部的人口生态学计划提供资金支持。未来气候变化对北极物种的影响是一个很大的不确定性和关注的来源，自上次冰期以来，北极经历了巨大的气候变化。 因此，研究生物对以前扰动的反应可能会提供重要的证据，说明北极物种的遗传多样性，饮食和地理范围将如何被未来的全球气候变化所改变。利用DNA分析，主要研究人员将根据白令吉亚三个地方的样本，研究贫瘠土地上的驯鹿和一匹灭绝的北极马的遗传多样性历史。从永久冻土中发现的骨头是古代DNA的极好来源，可以用14 C测年。最近的两项遗传学研究分析了北极永久冻土中埋藏的棕熊骨骼的DNA序列，发现了过去4万年来三个不同的遗传时代的证据，每个时代都以人口更替事件为标志。这些以前未被识别的时代是由来自35000（ka）BP以上的标本，21至10 ka BP的标本和现代人群的DNA序列定义的。 古气候研究提供的证据表明，这些时期之间的人口周转可以解释为气候变化有关的威斯康星州中部interstadial，末次冰期最大，全新世。然而，古环境的数据是稀疏和不确定的，这些遗传模式尚未在其他物种中得到验证。作为食草动物，驯鹿和马代表了与棕熊不同的营养水平，两个物种都专门消耗不同类型的植被（分别是苔原和草原）。 主要研究人员预测，生态系统范围内的气候变化不利于大型食草动物及其捕食者，这将导致这两个物种在所有三个地方的人口周转同步周期。这些变化应该与先前在棕熊和灰狼中观察到的变化相匹配。类似的区域或地方生态系统变化将表现为局部地区的同步周期。相比之下，两个物种的不同模式的遗传变化将意味着在苔原/森林的优势或存在新的物种特定的竞争对手和/或捕食者的变化。无论哪种情况，这项研究都将为气候变化对北极哺乳动物遗传多样性的潜在作用提供重要证据。 主要研究人员将确定环境变化的具体因素，并通过研究所有三个地点的三个独立类别的环境替代物来重建过去的北极环境。首先，他们将为DNA研究中分析的遗骸开发稳定的同位素图谱。这些剖面将作为区域气候变化的替代物，并允许推断动物饮食的变化。第二，他们将使用植入食草动物牙齿中的植物材料，重建两种食草动物利用的当地植物群的变化。第三，他们将利用现有的花粉记录和其他古环境数据来重建观察到的遗传更替期间的区域植被和一般气候。重要的是，他们将对来自白令吉亚两种食草动物的300块骨头进行14 C年代测定，这将把他们的结果放在一个时间背景下，以便与现有的气候数据相结合。 边界影响：所有数据将被放置在公共领域，以供未来新技术和新问题的出现。此外，这项研究将培养一群学生进行尖端的跨学科研究，包括遗传学，花粉分析，高分辨率放射性碳测年和稳定同位素生态学。

This is a collaborative proposal by Principal Investigators at the University of California-Los Angles and Santa Cruz, University of Alaska-Fairbanks, and the Smithsonian Institution. This award will be supported with funds from the Population Ecology Program in the Division of Biology and Arctic Natural Sciences Program. The effects of future climatic change on arctic species are a source of great uncertainty and concern and the Arctic has experienced large changes in climate since the last glacial cycle. Therefore, the study of biotic responses to the previous perturbations may provide important evidence of how the genetic diversity, diet, and geographic range of arctic species will be altered by future global climate change. Using DNA analysis, the Principal Investigators will examine the history of genetic diversity in the barren-ground caribou and an extinct arctic horse based on samples from three localities in Beringia. Bones recovered from the permafrost are an excellent source of ancient DNA and can be 14C dated. Two recent genetic studies analyzed DNA sequences from brown bear bones entombed in the arctic permafrost and found evidence of three distinct genetic epochs over the past 40,000 years, each marked by population turnover events. These previously unrecognized epochs are defined by DNA sequences from specimens older than 35 thousand (ka) BP, from specimens 21 to 10 ka BP, and by sequences from modern populations. Paleoclimate studies provide evidence that population turnover between these periods may be explained by changing climate relating to the mid-Wisconsin interstadial, the last glacial maximum, and the Holocene. However, paleoenvironmental data are sparse and inconclusive and these genetic patterns have not been verified in other species. As herbivores, caribou, and horses represent a different trophic level from brown bears and both species specialize on consuming different types of vegetation (tundra and grass-steppe, respectively). The Principal Investigators predict that ecosystem-wide climate change unfavorable to large herbivores and their predators would result in synchronous cycles of population turnover in both species across all three localities. These changes should match those previously observed in the brown bear and gray wolf. Similar regional or local ecosystem change would be manifest as synchronous cycles in a subset of localities. In contrast, differing patterns of genetic change in the two species would imply a change in the tundra/forest dominance or the presence of new species-specific competitors and/or predators. In either case, the study will provide important evidence of the potential role of climate change on genetic diversity in arctic mammals. The Principal Investigators will identify specific agents of environmental change and reconstruct past arctic environments through study of three independent classes of environmental surrogates in all three locations. First, they will develop stable isotope profiles for the remains analyzed in the DNA study. These profiles will serve as proxies for regional climate change and allow changing animal diets to be inferred. Second, they will use plant material imbedded in the teeth of herbivores to reconstruct the changes in local flora utilized by the two herbivores. Third, they will utilize existing pollen records and other paleoenvironmental data to reconstruct the regional vegetation and general climate during periods of observed genetic turnover. Importantly, they will 14C date 300 bones from the two herbivore species across Beringia which will place their results in a temporal context that will allow integration with existing climate data. Boarder Impact: All data will be placed in the public domain for future studies as new techniques and questions arise. Additionally, this research will train a group of students in cutting-edge, interdisciplinary research that incorporates genetics, pollen analysis, high-resolution radiocarbon dating, and stable isotope ecology.