Dissertation Research: Molecular mechanisms underlying rapid adaptive divergence in the Swamp Sparrow

论文研究：沼泽麻雀快速适应性分化的分子机制

• 批准号: 1501471
• 负责人: Irby Lovette
• 金额: $ 2.02万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1501471&HistoricalAwards=false
• 关键词: Dissertation; Research; Molecular; mechanisms; underlying

Populations of a single species that live in different geographic regions often diverge as natural selection drives adaptation to the local environment. Understanding the processes of divergence and local adaptation is of particular importance in this contemporary era of rapidly changing environments. The coastal salt marshes of North America provide excellent systems in which to study rapid adaptive divergence, given that these habitats have formed within the last 15,000 years and represent novel selective environments for their inhabitants. Within many independent lineages of birds, there is a strong pattern of evolving larger bills and darker plumage after colonizing coastal salt marshes, suggesting that these traits offer a selective advantage. This project will allow identification of the genetic basis of divergence in these traits, and provide a window into the evolutionary mechanisms underlying local adaptation. This project will also provide hands-on training for graduate and undergraduate students, and will provide useful information for the conservation of coastal bird populations. Two locally adapted subspecies of the Swamp Sparrow exist in the northeastern US: A brown inland form with a small bill, and a dark grey coastal form with a large bill. Preliminary DNA sequence (ddRAD) data reveal that the two forms are very similar, but several regions of the genome are highly differentiated between them. The natural history of coastal Swamp Sparrows suggests that strong directional selection may have influenced sequence variation in these highly differentiated regions. To test this hypothesis, patterns of genome-wide divergence will be surveyed by generating additional DNA sequence data for each differentiated region; these will be statistically examined for molecular signatures of selective sweeps. This project provides an important test of this emerging statistical methodology.

生活在不同地理区域的单个物种的种群通常会发散，因为自然选择可以适应当地环境。在这个迅速变化的环境中，了解差异和局部适应的过程尤其重要。北美的沿海盐沼提供了出色的系统来研究快速自适应差异，鉴于这些栖息地在过去15，000年内已形成，并代表了其居民的新型选择环境。在许多独立的鸟类谱系中，在殖民沿海盐沼后会发展出更大的钞票和较暗的羽毛，这表明这些特征具有选择性的优势。该项目将允许在这些特征中识别差异的遗传基础，并为局部适应的进化机制提供一个窗口。该项目还将为研究生和本科生提供动手培训，并为沿海鸟类种群的保护提供有用的信息。美国东北部存在两个沼泽麻雀的本地改编的亚种：棕色的内陆形式，带有小账单，还有一个深灰色的沿海形式，带有大账单。初步的DNA序列（DDRAD）数据表明，这两种形式非常相似，但是基因组的几个区域之间有高度区分。 沿海沼泽麻雀的自然历史表明，强烈的方向选择可能影响了这些高度分化的区域的序列变化。为了检验这一假设，将通过为每个区分区域生成其他DNA序列数据来调查全基因组差异的模式。这些将在统计上检查选择性扫描的分子特征。该项目提供了这种新兴统计方法的重要测试。